N Jb Miner Abh2008 Vol 1852 p 199ndash213 Stuttgart November 2008 published online 2008copy by E Schweizerbartrsquosche Verlagsbuchhandlung 2008
DOI 1011270077-775720080118 0077-7757080118 $ 375 copy 2008 E Schweizerbartrsquosche Verlagsbuchhandlung D-70176 Stuttgart
Introduction
The metallogenetic district of Baia Mare represents the NW part of the Neogene Volcanic Chain inside within the Romanian segment of the Carpathian Mountains (Eastern Carpathians) The Baia Mare district is positioned at the intersection of the E-trending Dragoş Vodă fault system and the NNW-trending late Miocene (ca 13ndash7 Ma) vol-canic belt The Baia Mare district comprises the following major deposits and camps (from NW to SE) Oaş Moun-tains Ilba-Nistru (W Gutacirci Mts) Săsar-Dealul Crucii etc (Central Gutacirci Mts around the city of Baia Mare itself) Herja-Baia Sprie-Şuior-Cavnic-Baiuţ (E Gutacirci Mts) The Toroiaga deposit at Baia Borşa ca 60 km ENE of Baia Mare also belongs to the Baia Mare district Each de-posit may contain many dozens of individual veins each hundreds of m or even several km in length of varying width and depth to 1000 m or more Vein strike tends to be specifi c to individual deposits eg typically E-W in Baia Sprie or NNEndashSSW in Cavnic The vein systems feature extensive zonation although patterns vary exten-
sively from deposit to deposit and may in some cases be telescoped or absent altogether
The majority of the deposits in the Baia Mare district are epithermal and they contain a great number of (domi-nantly Sb-) sulphosalts associated with the base metal ores The district is internationally recognised for the fi rst description of several Pb-As-Sb sulphosalt species fel-soumlbanyite (Kenngott 1853) semseyite (Krenner 1881) and andorite (Krenner 1893) in the Baia Sprie area fuumlloumlppite (Finaly amp Koch 1929) from Dealul Crucii and fi zelyite (Krenner amp Loczka 1925) from Herja
The presence of Bi minerals in the Baia Mare Neogene metallogenetic district was however recognised more recently Steclaci (in Szoumlke amp Steclaci 1962) mention trace amounts of Bi-minerals from veins at Toroiaga (Baia Borşa) The fi rst documented occurrence of Bi-sulphosalts was described by Cook (1997) in veins from the same Baia Borşa area The investigated samples contain matildite bismuthinite derivatives (aikinite friedrichite krupkaite hammarite lindstroumlmite and gladite) nuffi eldite berryite and various members of the lillianite homologous series
Bismuth sulphosalts from the galena-matildite series in the Cremenea vein Suior Baia Mare district Romania
Gheorghe Damian Cristiana L Ciobanu Nigel J Cook and Floarea Damian
With 9 fi gures and 1 table
Abstract Ag-Bi-sulphosalts are reported from Cu-rich ores within base metal mineralization situated beneath Au-ores below level 750-800 m in the Cremenea vein of the Şuior epithermal vein deposit Baia Mare region Romania Microanalytical data show the presence of a homogeneous unnamed phase with empirical composition [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] showing light Bi-enrichment relative to ideal AgPbBiS3 Intergrowths of galena and matildite with a characteristic basket-weave texture are interpreted as decomposition products of AgPbBiS3 and other phases along the PbS-AgBiS2 join Parallel lamellar intergrowths have bulk compositions approximating Pb4Ag56Bi56S152 These compositions represent natural equivalents of phases synthesized in the PbS-AgBiS2 system Although galena and matildite end-members and decomposition-products may be formed at still lower temperatures interpretation of observed textures and microanalytical data in combination with published phase diagrams indicate formation of the intermediate phases at temperatures as low as 144 degC Similarly we interpret minimum temperatures of initial pre-cipitation as melts (in the range 40-70 AgBiS2) to be in the range 230ndash175 degC The observed Bi excess may be a factor preventing decomposition of AgPbBiS3 into galena and matildite
Key words Şuior epithermal vein deposit Baia Mare Ag-Bi-sulphosalts galena-matildite series unnamed phases
200 G Damian et al
Cook (1998) reported a second occurrence of Bi-sul-phosalts in the area from the central part of Băiuţ-Văratic Signifi cantly this assemblage of sulphosalts [represent-ed by lillianite homologues (lillianite-gustavite hey-rovskyacuteite lsquoschirmeritersquo) pekoite bismuthinite matildite berryite wittichenite and pavonite homologues] are dis-tributed in Cu-ores Damian amp Costin (1999) also identi-fi ed lillianite gustavite vikingite and heyrovskyacuteite from the NW part of the Băiuţ-Văratic deposit A third occur-rence of Bi-sulphosalts was reported from the eastern part from Baia Mare district at Nistru (Damian amp Cook 1999 Damian et al 2000) In the Nistru Cu-ores Bi-sulphosalts are represented by intermediate members of the lillianite-gustavite solid solution series bismuthinite derivatives (krupkaite gladite pekoite) cosalite and matildite
Bi-sulphosalts have now been shown to be present in deposits from all segments of the Neogene Carpathian Arc Bi-mineral assemblages are particularly characteris-tic and widespread in the Banska Štiavnica-Hodruša ore district Slovakia (eg Kovalenker et al 1993 JeleŇ et al 2000) Assemblages here may be complex with emplectite matildite hodrushite aikinite wittichenite Ag-wittichenite paderaite vikingite gladite krupkaite hammarite lindstroumlmite friedrichite and other minerals reported Various unnamed phases in the Ag-Cu-Pb-Bi-S system were reported by JELEŇ et al (2000)
The occurrence of Bi-minerals in the Beregovo ore fi eld Ukraine was fi rst reported by Matkovsky et al (1987) and Remeshilo et al (1989) who described bis-muthinite berryite lillianite-gustavite series lsquoschirmer-itersquo and cosalite Biruk amp Skakun (2000) described a new occurrences of the Bi-minerals developed at the deep levels of Beregovo deposits and noted the presence of bis-muthinite derivatives (gladite aikinite friedrichite lind-stroumlmite hammarite krupkaite pekoite bismuthinite) lillianite homologues (lillianite ourayite heyrovskyacuteite gustavite treasureite vikingite eskimoite schirmerite) pavonite homologues (mummeite benjaminite) matildite galenobismutite cosalite paderaite emplectite proudite berryite wittichenite součekite and nuffi eldite
Although not common Bi-sulphosalts are also known from Neogene deposits of the South Apuseni Mts Ro-mania Bismuthinite emplectite and galenobismutite are known historically (eg from Picircricircul lui Avram Socoles-cu et al 1963 see review in Cook et al 2004) Cook amp Ciobanu (2004) provided data for lillianite and pavonite homologues and bismuthinite derivatives from the Larga-Faţa Băii system and Ciobanu et al (2005a) have recent-ly described a wide range of Bi-sulphosalts from within low-sulphidation epithermal mineralization at Săcăracircmb Minor amounts of Bi-sulphosalts have subsequently been noted from other deposits in the South Apuseni Mts in-
cluding those of the Stănija area (Ciobanu amp Cook un-publ data) The apparently widespread development of Bi-sulphosalts in veins from across the Inner Carpathian arc may also be important for understanding gold enrich-ment in parts of the deposits since in a number of the examples referred to above there is a marked spatial as-sociation with gold
Geological and metallogenetic background
The Baia Mare metallogenetic district (Fig 1) represents the NW part of the Neogene Volcanic Chain inside the Carpathian Mountains The district is one of the most pro-ductive in Romania and includes both gold and base metal ore deposits According to Balintoni (1997) the Baia Mare ore district occurs within a triple junction between the Preapuliane Getic and Euroasian Cratons Both mag-matic and metallogenetic activity is associated with the subduction of two lithospheric blocks (Alcapa and Tisia) at the eastern border of the European plate (ŞEGHEDI et al 2004) and has been related to the post-collision compres-sive phase of that subduction event The location of the Neogene magmatic rocks and associated ore deposits are controlled by the E-W striking Dragoş-Vodă crustal frac-ture (Popescu 1986) This has recently been interpreted as a ldquotranstensional wrench setting representing the northern sinistral confi ning strike-slip fault relating to a wrench corridor of the eastward extruding TisiandashDacia and Alcapa blocksrdquo (Neubauer et al 2005) Emplacement of volcan-ics release and focussing of ore-forming fl uids and thus localization of main ore deposits in the Baia Mare district took place along the Dragoş-Vodă master fault and subor-dinate (mostly NNWndashSSE-trending) cross-faults
Most Neogene calc-alkaline magmatism in the Baia Mare region resulted from melting of a heterogeneous as-thenospheric mantle source modifi ed by addition of fl u-ids and sediments (ŞEGHEDI et al 2004) A migration of magmatism has been noticed from east to west across the Baia Mare area Thus the oldest magmatic products oc-cur in the western part whereas younger magmatic rocks are dominantly found in the east of the area The subduc-tion that generated this magmatism fi rst occurred in stress conditions with comprehensive tendencies followed by extensional conditions (Popescu 1994) The existence of a subduction event at the beginning of the Miocene is be-lieved to have led to formation of a magma reservoir at the crustal level which was subsequently activated through collision of the Intra-Carpathian microplate with the East-European plate
The pre-Neogene basement consists of metamorphic rocks and Paleogene sedimentary rocks The metamor-
Bi-sulphosalts at Şuior 201
phic rocks of Lower Cambrian age belong to the medium Dacides and the Paleogene sedimentary rocks represent sequences from the Transcarpathian Flysch (SĂndulescu 1984) Neogene sedimentary molasse deposits are repre-sented by Badenian Sarmatian Pannonian and Pontian formations which are contemporary with the volcanic activity in the Baia Mare area The Paleogene molasse de-posits unconformably overlie the metamorphic basement
According to GIUŞCĂ et al (1973) and BorCOŞ et al (1973) volcanic activity from the Gutacirci Mts took place in three stages which could be dated biostratigraphi-cally The fi rst stage (Badenian-Buglovian) was acid in character whereas the other two (Sarmatian-Pontian and Pontian-Pliocene) were intermediate in character Based on K-Ar data the volcanic rocks are Lower Sarmatian to Upper Pannonian in age (ie 134ndash90 Ma Edelstein et al 1992) Only the fi nal basaltic stage in the Gutacirci Mts belongs to the Upper Pannonian-Pontian (8ndash69 Ma)
Intrusive bodies of the Baia Mare district are typically younger than their host lava fl ows of the same calc-al-kaline trend For example the intruvive bodies at Nistru are dated at 109 Ma (KAr F Damian 1995) whereas the pyroxene andesite lava fl ow of Seini type are dated at 134ndash121 Ma (KAr Edelstein et al 1992) Intrusive rocks are in general represented by microdiorites quartz-diorites quartz-monzodiorites (Damian 1995) micro-granodiorites and tonalites These intrusive bodies have an important role in localization of ore deposits and they are believed to derive from a large underlying pluton (BORCOŞ 1994) commonly referred to as the ldquoBaia Mare batholithrdquo by later workers (eg Bailly et al 1998 Grancea et al 2002) K-Ar dating of intrusions in the Eastern part of the Gutacirci Mts which are not directly related to the lava fl ows indicates ages of 11ndash9 million years
Metallogenetic activity corresponds to three distinct phases (GIUŞCĂ et al 1973) and overlaps with the calc-al-
kaline - intermediate magmatic activity during the second eruption cycle According to radiometric data K-Ar and Ar-Ar (Lang et al 1994 Peacutecskay et al 1995a b Kovacs et al 2001) the metallogenetic activity is restricted to the Pannonian (115ndash79 Ma)
Although ores have a dominant base metal character Au-Ag and Cu ores are also present In particular the upper parts of Cu-(Zn-Pb) veins may contain economi-cally signifi cant quantities of Au and Ag A polyascend-ent character can be observed within the base metal veins but in the gold-dominant veins and also those of narrow dimensions a monoascendent character is considered to dominate (Damian et al 2003) The poly-ascendant char-acter of base metal ores in the Baia Mare district could be due to changes in their chemical composition as well as the pulsing character of the hydrothermal solutions and also the reactivation of fractures as a result of the local tectonics Penetration of the magmatic intrusions into the upper levels of the volcanic structures created a system of stress fractures that facilitated access for the mineralizing fl uids and permitted mixing with meteoric waters
Emplacement of the intrusions was accompanied by alteration of the host rock The central zones of the in-trusions show pervasive potassic alteration with index minerals such as orthoclase and biotite as well as seric-ite The potassic zones in which pyrite and chalcopyrite are present as well as magnetite resembles that found in porphyry-type environments Propylitic alteration is more typical of subvolcanic bodies A zonation is expressed by internal propylitization with actinolite in the central part of the intrusion surrounded by external zone with epidote and a third outer one with chlorite The spatial association between mineralization and magmatic intrusions in the Baia Mare district suggests a direct genetic relationship between the intrusion-generating magma and hydrother-mal circulation Mineralization is mainly associated with
Fig 1 Geological sketch map of the Baia Mare area showing loca-tion of the Şuior deposit and other deposits in the district mentioned in the text Inset shows a general map of the Carpathian region and location of the Baia Mare District (box)
202 G Damian et al
phyllic alteration in deposits with Au-enrichment at up-per levels adularia-type andor argillic alteration are also typical Chloritization and phyllic alteration are strongly associated with the occurrence of Cu mineralization in the Baia Mare district Structural control association with magmatic intrusions the mineralogical composition of the ores and association with distinct types of hydrothermal al-teration are indicative of an adularia-sericite type (Heald et al 1987) ie low sulphidation epithermal system
Cremenea-Şuior
The polymetallic Şuior-Cremenea deposit is one of the most economically important within the Baia Mare dis-trict Structural control of the mineralization is particularly evident since the Cremenea vein system is positioned di-rectly on the E-W (Baia Sprie-Şuior) regional alignment The latter represents a shear zone (Popescu 1986) part of the major E-W Dragoş-Vodă fracture The Cremenea vein is in exact alignment with the extension of the Principal vein from Baia Sprie suggesting that the two belong to the same mineralised structure (Baia Sprie-Şuior metal-logenetic structure)
The Cremenea lsquoveinrsquo is an important ndash and in many ways exceptional ndash orebody in the Baia Mare district due to its size at upper levels the vein extends ca 800 m along strike reaching a depth of 1200 m with a width between 2 and 40 m The maximum width was at upper levels and was exploited by open pit ores were predominantly of Au-Ag type According to BORCOŞ et al (1973) calling the orebody a lsquoveinrsquo is inappropriate because the lsquoveinrsquo actually has a lens-like shape Berbeleac (1998) report-ed that the Cremenea vein contains gt 30 Mt ore Beneath the Au-Ag ores at upper levels base metal mineralization is predominant in middle and lower parts Telescoping is recognised in the middle part of the vein with Au-Ag mineralization overlapping the base metal ores The vein cavity contains explosion breccias made up of fragments of andesite and sedimentary rocks all highly silicifi ed sericitized and adularized This is also recognized in Baia Sprie veins supporting the unity of the Baia Sprie-Şuior structure
The Cremenea vein like the Principal vein in Baia Sprie lies on the northern side of a subvolcanic intrusion of porphyritic microdiorite which is considered to belong to the pyroxene-amphibole andesites (Jereapăn phase) The porphyry microdiorite intrudes sedimentary rocks of Paleogene Sarmatian and Pannonian age as well as Pan-nonian quartz-andesites and pyroxene andesites Accord-ing to their respective radiometric data the age of the in-trusion is considered to be Pontian by BORCOŞ et al (1973) and Pannonian by Edelstein et al (1992) The porphyry
microdiorite in Şuior is the eastern extension of the same dyke in Baia Sprie
Stanciu et al (1970) described adularization silici-fi cation and argillization as the most important types of hydrothermal alteration associated with Au-Ag ores in the upper part of the Cremenea vein
Brecciated textures are ubiquitous within the vein with heterogeneous fragments of sedimentary and erup-tive rocks cemented by quartz and sulphides In the upper part the predominant textures are lightly banded with a collomorphic aspect consisting of mm-scale opal chal-cedony quartz and sulphides In the lower part of the ore deposit where the mineralization has a predominantly base-metal character the texture is massive and banded The parallel banded character is expressed by an alter-nation of the different varieties of quartz and amorphous silica At upper levels there were also frequent geodes with quartz crystals Although transition from Au-Ag ore to base-metal ore is gradual the presence of a clear vertical zonation very similar to that at Baia Sprie can be observed with an upper Au-Ag-bearing part and a lower part enriched in base metals In comparison with Baia Sprie however Şuior lacks a clear cupriferous zone specifi c to lower levels with Cu distributed throughout the vertical extent of the deposit The upper Au-Ag part consists of pyrite wurtzite sphalerite arsenopyrite chal-copyrite tetrahedrite galena boulangerite and marcasite Below 800 m sphalerite and galena are predominant frequently associated with chalcopyrite Inclusions of Sb-sulphosalts (tetrahedrite proustite and pyrargyrite) appear frequently within galena Beneath the gold zone Cu-rich ores (pyrite-chalcopyriteplusmnarsenopyrite) may be present at the northern boundary of the orebody They may also in-clude Bi-minerals as described below In this zone the vein width is reduced to just 15ndash30 cm
Homogenisation temperature of two-phase fl uid inclu-sions in quartz varies between 230 and 280 ordmC (BORCOŞ et al 1973) Determination of fl uid inclusion homogenisa-tion temperatures was from quartz from upper and median levels As in all deposits of the Baia Mare area formation temperatures in the lower base-metal mineralization are believed to have been signifi cantly higher Similar conclu-sions were reached by Pomacircrleanu (1971)
According to BORCOŞ et al (1973) native gold has a sporadic presence Damian and Damian (1998) have identifi ed microscopic native gold in both Au-Ag ore and base metal ores In the upper Au-Ag part of the vein native gold is associated with quartz (80 ) and subordinately with pyrite and sphalerite In the base metal ores native gold is predominantly associated with sulphides (25 of gold in pyrite 34 in sphalerite 24 in galena 05 in arsenopyrite and 05 in tetrahedrite) and with quartz
Bi-sulphosalts at Şuior 203
(16 ) The fi neness of native gold is typically between 700 and 755
Description and microanalysis of the Bi-mineral assemblages
Methodology
Electron probe microanalytical data were collected us-ing a Cameca SX-51 instrument at Adelaide Microscopy Adelaide Australia Operating conditions were 20 kV ac-celerating voltage and 195 na beam current Standards used were as follows Bi2Se3 (Bi) PbS (Pb S) Ag (Ag) Cu (Cu) Sb2S3 (Sb) Te (Te) These data are supplemented by data collected using a Hitachi scanning electron micro-scope equipped with an Oxford Instruments wavelength-dispersive spectrometer at the Natural History Museum University of Oslo Blocks were polished to 01 microm using synthetic diamond compounds Electron probe micro-analyses are accurate to +- 2 relative standard Came-
ca-supplied data reduction packages and no matrix cor-rection coeffi cients were used following experience with similar material from other deposits Minimum detection limits are on the range of 003 wt for all elements all samples were carbon-coated prior to SEM study and mi-croprobe analysis
Description and results
The samples containing Bi-sulphosalts which were exam-ined in this study are located in the base metal mineraliza-tion of Cremenea vein (Fig 2) below level 750ndash800 m The Bi-sulphosalts occur however within a Cu-rich ore (pyrite-chalcopyrite assemblage) similar to that identi-fi ed at Toroiaga (Cook 1997 1998) Nistru (Damian amp Cook 1999 Damian et al 2000) and at Băiuţ-Văratic (Cook 1998 Damian et al 2000) In the Cremenea-Şuior orebody such association is found typically close to the northern contact of the vein with the intrusive host rock The gangue consists of quartz
Fig 2 NNW-SSE cross-section across the Şuior-Cremenea orebody with geological set-ting and location of specimens described in this study
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
200 G Damian et al
Cook (1998) reported a second occurrence of Bi-sul-phosalts in the area from the central part of Băiuţ-Văratic Signifi cantly this assemblage of sulphosalts [represent-ed by lillianite homologues (lillianite-gustavite hey-rovskyacuteite lsquoschirmeritersquo) pekoite bismuthinite matildite berryite wittichenite and pavonite homologues] are dis-tributed in Cu-ores Damian amp Costin (1999) also identi-fi ed lillianite gustavite vikingite and heyrovskyacuteite from the NW part of the Băiuţ-Văratic deposit A third occur-rence of Bi-sulphosalts was reported from the eastern part from Baia Mare district at Nistru (Damian amp Cook 1999 Damian et al 2000) In the Nistru Cu-ores Bi-sulphosalts are represented by intermediate members of the lillianite-gustavite solid solution series bismuthinite derivatives (krupkaite gladite pekoite) cosalite and matildite
Bi-sulphosalts have now been shown to be present in deposits from all segments of the Neogene Carpathian Arc Bi-mineral assemblages are particularly characteris-tic and widespread in the Banska Štiavnica-Hodruša ore district Slovakia (eg Kovalenker et al 1993 JeleŇ et al 2000) Assemblages here may be complex with emplectite matildite hodrushite aikinite wittichenite Ag-wittichenite paderaite vikingite gladite krupkaite hammarite lindstroumlmite friedrichite and other minerals reported Various unnamed phases in the Ag-Cu-Pb-Bi-S system were reported by JELEŇ et al (2000)
The occurrence of Bi-minerals in the Beregovo ore fi eld Ukraine was fi rst reported by Matkovsky et al (1987) and Remeshilo et al (1989) who described bis-muthinite berryite lillianite-gustavite series lsquoschirmer-itersquo and cosalite Biruk amp Skakun (2000) described a new occurrences of the Bi-minerals developed at the deep levels of Beregovo deposits and noted the presence of bis-muthinite derivatives (gladite aikinite friedrichite lind-stroumlmite hammarite krupkaite pekoite bismuthinite) lillianite homologues (lillianite ourayite heyrovskyacuteite gustavite treasureite vikingite eskimoite schirmerite) pavonite homologues (mummeite benjaminite) matildite galenobismutite cosalite paderaite emplectite proudite berryite wittichenite součekite and nuffi eldite
Although not common Bi-sulphosalts are also known from Neogene deposits of the South Apuseni Mts Ro-mania Bismuthinite emplectite and galenobismutite are known historically (eg from Picircricircul lui Avram Socoles-cu et al 1963 see review in Cook et al 2004) Cook amp Ciobanu (2004) provided data for lillianite and pavonite homologues and bismuthinite derivatives from the Larga-Faţa Băii system and Ciobanu et al (2005a) have recent-ly described a wide range of Bi-sulphosalts from within low-sulphidation epithermal mineralization at Săcăracircmb Minor amounts of Bi-sulphosalts have subsequently been noted from other deposits in the South Apuseni Mts in-
cluding those of the Stănija area (Ciobanu amp Cook un-publ data) The apparently widespread development of Bi-sulphosalts in veins from across the Inner Carpathian arc may also be important for understanding gold enrich-ment in parts of the deposits since in a number of the examples referred to above there is a marked spatial as-sociation with gold
Geological and metallogenetic background
The Baia Mare metallogenetic district (Fig 1) represents the NW part of the Neogene Volcanic Chain inside the Carpathian Mountains The district is one of the most pro-ductive in Romania and includes both gold and base metal ore deposits According to Balintoni (1997) the Baia Mare ore district occurs within a triple junction between the Preapuliane Getic and Euroasian Cratons Both mag-matic and metallogenetic activity is associated with the subduction of two lithospheric blocks (Alcapa and Tisia) at the eastern border of the European plate (ŞEGHEDI et al 2004) and has been related to the post-collision compres-sive phase of that subduction event The location of the Neogene magmatic rocks and associated ore deposits are controlled by the E-W striking Dragoş-Vodă crustal frac-ture (Popescu 1986) This has recently been interpreted as a ldquotranstensional wrench setting representing the northern sinistral confi ning strike-slip fault relating to a wrench corridor of the eastward extruding TisiandashDacia and Alcapa blocksrdquo (Neubauer et al 2005) Emplacement of volcan-ics release and focussing of ore-forming fl uids and thus localization of main ore deposits in the Baia Mare district took place along the Dragoş-Vodă master fault and subor-dinate (mostly NNWndashSSE-trending) cross-faults
Most Neogene calc-alkaline magmatism in the Baia Mare region resulted from melting of a heterogeneous as-thenospheric mantle source modifi ed by addition of fl u-ids and sediments (ŞEGHEDI et al 2004) A migration of magmatism has been noticed from east to west across the Baia Mare area Thus the oldest magmatic products oc-cur in the western part whereas younger magmatic rocks are dominantly found in the east of the area The subduc-tion that generated this magmatism fi rst occurred in stress conditions with comprehensive tendencies followed by extensional conditions (Popescu 1994) The existence of a subduction event at the beginning of the Miocene is be-lieved to have led to formation of a magma reservoir at the crustal level which was subsequently activated through collision of the Intra-Carpathian microplate with the East-European plate
The pre-Neogene basement consists of metamorphic rocks and Paleogene sedimentary rocks The metamor-
Bi-sulphosalts at Şuior 201
phic rocks of Lower Cambrian age belong to the medium Dacides and the Paleogene sedimentary rocks represent sequences from the Transcarpathian Flysch (SĂndulescu 1984) Neogene sedimentary molasse deposits are repre-sented by Badenian Sarmatian Pannonian and Pontian formations which are contemporary with the volcanic activity in the Baia Mare area The Paleogene molasse de-posits unconformably overlie the metamorphic basement
According to GIUŞCĂ et al (1973) and BorCOŞ et al (1973) volcanic activity from the Gutacirci Mts took place in three stages which could be dated biostratigraphi-cally The fi rst stage (Badenian-Buglovian) was acid in character whereas the other two (Sarmatian-Pontian and Pontian-Pliocene) were intermediate in character Based on K-Ar data the volcanic rocks are Lower Sarmatian to Upper Pannonian in age (ie 134ndash90 Ma Edelstein et al 1992) Only the fi nal basaltic stage in the Gutacirci Mts belongs to the Upper Pannonian-Pontian (8ndash69 Ma)
Intrusive bodies of the Baia Mare district are typically younger than their host lava fl ows of the same calc-al-kaline trend For example the intruvive bodies at Nistru are dated at 109 Ma (KAr F Damian 1995) whereas the pyroxene andesite lava fl ow of Seini type are dated at 134ndash121 Ma (KAr Edelstein et al 1992) Intrusive rocks are in general represented by microdiorites quartz-diorites quartz-monzodiorites (Damian 1995) micro-granodiorites and tonalites These intrusive bodies have an important role in localization of ore deposits and they are believed to derive from a large underlying pluton (BORCOŞ 1994) commonly referred to as the ldquoBaia Mare batholithrdquo by later workers (eg Bailly et al 1998 Grancea et al 2002) K-Ar dating of intrusions in the Eastern part of the Gutacirci Mts which are not directly related to the lava fl ows indicates ages of 11ndash9 million years
Metallogenetic activity corresponds to three distinct phases (GIUŞCĂ et al 1973) and overlaps with the calc-al-
kaline - intermediate magmatic activity during the second eruption cycle According to radiometric data K-Ar and Ar-Ar (Lang et al 1994 Peacutecskay et al 1995a b Kovacs et al 2001) the metallogenetic activity is restricted to the Pannonian (115ndash79 Ma)
Although ores have a dominant base metal character Au-Ag and Cu ores are also present In particular the upper parts of Cu-(Zn-Pb) veins may contain economi-cally signifi cant quantities of Au and Ag A polyascend-ent character can be observed within the base metal veins but in the gold-dominant veins and also those of narrow dimensions a monoascendent character is considered to dominate (Damian et al 2003) The poly-ascendant char-acter of base metal ores in the Baia Mare district could be due to changes in their chemical composition as well as the pulsing character of the hydrothermal solutions and also the reactivation of fractures as a result of the local tectonics Penetration of the magmatic intrusions into the upper levels of the volcanic structures created a system of stress fractures that facilitated access for the mineralizing fl uids and permitted mixing with meteoric waters
Emplacement of the intrusions was accompanied by alteration of the host rock The central zones of the in-trusions show pervasive potassic alteration with index minerals such as orthoclase and biotite as well as seric-ite The potassic zones in which pyrite and chalcopyrite are present as well as magnetite resembles that found in porphyry-type environments Propylitic alteration is more typical of subvolcanic bodies A zonation is expressed by internal propylitization with actinolite in the central part of the intrusion surrounded by external zone with epidote and a third outer one with chlorite The spatial association between mineralization and magmatic intrusions in the Baia Mare district suggests a direct genetic relationship between the intrusion-generating magma and hydrother-mal circulation Mineralization is mainly associated with
Fig 1 Geological sketch map of the Baia Mare area showing loca-tion of the Şuior deposit and other deposits in the district mentioned in the text Inset shows a general map of the Carpathian region and location of the Baia Mare District (box)
202 G Damian et al
phyllic alteration in deposits with Au-enrichment at up-per levels adularia-type andor argillic alteration are also typical Chloritization and phyllic alteration are strongly associated with the occurrence of Cu mineralization in the Baia Mare district Structural control association with magmatic intrusions the mineralogical composition of the ores and association with distinct types of hydrothermal al-teration are indicative of an adularia-sericite type (Heald et al 1987) ie low sulphidation epithermal system
Cremenea-Şuior
The polymetallic Şuior-Cremenea deposit is one of the most economically important within the Baia Mare dis-trict Structural control of the mineralization is particularly evident since the Cremenea vein system is positioned di-rectly on the E-W (Baia Sprie-Şuior) regional alignment The latter represents a shear zone (Popescu 1986) part of the major E-W Dragoş-Vodă fracture The Cremenea vein is in exact alignment with the extension of the Principal vein from Baia Sprie suggesting that the two belong to the same mineralised structure (Baia Sprie-Şuior metal-logenetic structure)
The Cremenea lsquoveinrsquo is an important ndash and in many ways exceptional ndash orebody in the Baia Mare district due to its size at upper levels the vein extends ca 800 m along strike reaching a depth of 1200 m with a width between 2 and 40 m The maximum width was at upper levels and was exploited by open pit ores were predominantly of Au-Ag type According to BORCOŞ et al (1973) calling the orebody a lsquoveinrsquo is inappropriate because the lsquoveinrsquo actually has a lens-like shape Berbeleac (1998) report-ed that the Cremenea vein contains gt 30 Mt ore Beneath the Au-Ag ores at upper levels base metal mineralization is predominant in middle and lower parts Telescoping is recognised in the middle part of the vein with Au-Ag mineralization overlapping the base metal ores The vein cavity contains explosion breccias made up of fragments of andesite and sedimentary rocks all highly silicifi ed sericitized and adularized This is also recognized in Baia Sprie veins supporting the unity of the Baia Sprie-Şuior structure
The Cremenea vein like the Principal vein in Baia Sprie lies on the northern side of a subvolcanic intrusion of porphyritic microdiorite which is considered to belong to the pyroxene-amphibole andesites (Jereapăn phase) The porphyry microdiorite intrudes sedimentary rocks of Paleogene Sarmatian and Pannonian age as well as Pan-nonian quartz-andesites and pyroxene andesites Accord-ing to their respective radiometric data the age of the in-trusion is considered to be Pontian by BORCOŞ et al (1973) and Pannonian by Edelstein et al (1992) The porphyry
microdiorite in Şuior is the eastern extension of the same dyke in Baia Sprie
Stanciu et al (1970) described adularization silici-fi cation and argillization as the most important types of hydrothermal alteration associated with Au-Ag ores in the upper part of the Cremenea vein
Brecciated textures are ubiquitous within the vein with heterogeneous fragments of sedimentary and erup-tive rocks cemented by quartz and sulphides In the upper part the predominant textures are lightly banded with a collomorphic aspect consisting of mm-scale opal chal-cedony quartz and sulphides In the lower part of the ore deposit where the mineralization has a predominantly base-metal character the texture is massive and banded The parallel banded character is expressed by an alter-nation of the different varieties of quartz and amorphous silica At upper levels there were also frequent geodes with quartz crystals Although transition from Au-Ag ore to base-metal ore is gradual the presence of a clear vertical zonation very similar to that at Baia Sprie can be observed with an upper Au-Ag-bearing part and a lower part enriched in base metals In comparison with Baia Sprie however Şuior lacks a clear cupriferous zone specifi c to lower levels with Cu distributed throughout the vertical extent of the deposit The upper Au-Ag part consists of pyrite wurtzite sphalerite arsenopyrite chal-copyrite tetrahedrite galena boulangerite and marcasite Below 800 m sphalerite and galena are predominant frequently associated with chalcopyrite Inclusions of Sb-sulphosalts (tetrahedrite proustite and pyrargyrite) appear frequently within galena Beneath the gold zone Cu-rich ores (pyrite-chalcopyriteplusmnarsenopyrite) may be present at the northern boundary of the orebody They may also in-clude Bi-minerals as described below In this zone the vein width is reduced to just 15ndash30 cm
Homogenisation temperature of two-phase fl uid inclu-sions in quartz varies between 230 and 280 ordmC (BORCOŞ et al 1973) Determination of fl uid inclusion homogenisa-tion temperatures was from quartz from upper and median levels As in all deposits of the Baia Mare area formation temperatures in the lower base-metal mineralization are believed to have been signifi cantly higher Similar conclu-sions were reached by Pomacircrleanu (1971)
According to BORCOŞ et al (1973) native gold has a sporadic presence Damian and Damian (1998) have identifi ed microscopic native gold in both Au-Ag ore and base metal ores In the upper Au-Ag part of the vein native gold is associated with quartz (80 ) and subordinately with pyrite and sphalerite In the base metal ores native gold is predominantly associated with sulphides (25 of gold in pyrite 34 in sphalerite 24 in galena 05 in arsenopyrite and 05 in tetrahedrite) and with quartz
Bi-sulphosalts at Şuior 203
(16 ) The fi neness of native gold is typically between 700 and 755
Description and microanalysis of the Bi-mineral assemblages
Methodology
Electron probe microanalytical data were collected us-ing a Cameca SX-51 instrument at Adelaide Microscopy Adelaide Australia Operating conditions were 20 kV ac-celerating voltage and 195 na beam current Standards used were as follows Bi2Se3 (Bi) PbS (Pb S) Ag (Ag) Cu (Cu) Sb2S3 (Sb) Te (Te) These data are supplemented by data collected using a Hitachi scanning electron micro-scope equipped with an Oxford Instruments wavelength-dispersive spectrometer at the Natural History Museum University of Oslo Blocks were polished to 01 microm using synthetic diamond compounds Electron probe micro-analyses are accurate to +- 2 relative standard Came-
ca-supplied data reduction packages and no matrix cor-rection coeffi cients were used following experience with similar material from other deposits Minimum detection limits are on the range of 003 wt for all elements all samples were carbon-coated prior to SEM study and mi-croprobe analysis
Description and results
The samples containing Bi-sulphosalts which were exam-ined in this study are located in the base metal mineraliza-tion of Cremenea vein (Fig 2) below level 750ndash800 m The Bi-sulphosalts occur however within a Cu-rich ore (pyrite-chalcopyrite assemblage) similar to that identi-fi ed at Toroiaga (Cook 1997 1998) Nistru (Damian amp Cook 1999 Damian et al 2000) and at Băiuţ-Văratic (Cook 1998 Damian et al 2000) In the Cremenea-Şuior orebody such association is found typically close to the northern contact of the vein with the intrusive host rock The gangue consists of quartz
Fig 2 NNW-SSE cross-section across the Şuior-Cremenea orebody with geological set-ting and location of specimens described in this study
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 201
phic rocks of Lower Cambrian age belong to the medium Dacides and the Paleogene sedimentary rocks represent sequences from the Transcarpathian Flysch (SĂndulescu 1984) Neogene sedimentary molasse deposits are repre-sented by Badenian Sarmatian Pannonian and Pontian formations which are contemporary with the volcanic activity in the Baia Mare area The Paleogene molasse de-posits unconformably overlie the metamorphic basement
According to GIUŞCĂ et al (1973) and BorCOŞ et al (1973) volcanic activity from the Gutacirci Mts took place in three stages which could be dated biostratigraphi-cally The fi rst stage (Badenian-Buglovian) was acid in character whereas the other two (Sarmatian-Pontian and Pontian-Pliocene) were intermediate in character Based on K-Ar data the volcanic rocks are Lower Sarmatian to Upper Pannonian in age (ie 134ndash90 Ma Edelstein et al 1992) Only the fi nal basaltic stage in the Gutacirci Mts belongs to the Upper Pannonian-Pontian (8ndash69 Ma)
Intrusive bodies of the Baia Mare district are typically younger than their host lava fl ows of the same calc-al-kaline trend For example the intruvive bodies at Nistru are dated at 109 Ma (KAr F Damian 1995) whereas the pyroxene andesite lava fl ow of Seini type are dated at 134ndash121 Ma (KAr Edelstein et al 1992) Intrusive rocks are in general represented by microdiorites quartz-diorites quartz-monzodiorites (Damian 1995) micro-granodiorites and tonalites These intrusive bodies have an important role in localization of ore deposits and they are believed to derive from a large underlying pluton (BORCOŞ 1994) commonly referred to as the ldquoBaia Mare batholithrdquo by later workers (eg Bailly et al 1998 Grancea et al 2002) K-Ar dating of intrusions in the Eastern part of the Gutacirci Mts which are not directly related to the lava fl ows indicates ages of 11ndash9 million years
Metallogenetic activity corresponds to three distinct phases (GIUŞCĂ et al 1973) and overlaps with the calc-al-
kaline - intermediate magmatic activity during the second eruption cycle According to radiometric data K-Ar and Ar-Ar (Lang et al 1994 Peacutecskay et al 1995a b Kovacs et al 2001) the metallogenetic activity is restricted to the Pannonian (115ndash79 Ma)
Although ores have a dominant base metal character Au-Ag and Cu ores are also present In particular the upper parts of Cu-(Zn-Pb) veins may contain economi-cally signifi cant quantities of Au and Ag A polyascend-ent character can be observed within the base metal veins but in the gold-dominant veins and also those of narrow dimensions a monoascendent character is considered to dominate (Damian et al 2003) The poly-ascendant char-acter of base metal ores in the Baia Mare district could be due to changes in their chemical composition as well as the pulsing character of the hydrothermal solutions and also the reactivation of fractures as a result of the local tectonics Penetration of the magmatic intrusions into the upper levels of the volcanic structures created a system of stress fractures that facilitated access for the mineralizing fl uids and permitted mixing with meteoric waters
Emplacement of the intrusions was accompanied by alteration of the host rock The central zones of the in-trusions show pervasive potassic alteration with index minerals such as orthoclase and biotite as well as seric-ite The potassic zones in which pyrite and chalcopyrite are present as well as magnetite resembles that found in porphyry-type environments Propylitic alteration is more typical of subvolcanic bodies A zonation is expressed by internal propylitization with actinolite in the central part of the intrusion surrounded by external zone with epidote and a third outer one with chlorite The spatial association between mineralization and magmatic intrusions in the Baia Mare district suggests a direct genetic relationship between the intrusion-generating magma and hydrother-mal circulation Mineralization is mainly associated with
Fig 1 Geological sketch map of the Baia Mare area showing loca-tion of the Şuior deposit and other deposits in the district mentioned in the text Inset shows a general map of the Carpathian region and location of the Baia Mare District (box)
202 G Damian et al
phyllic alteration in deposits with Au-enrichment at up-per levels adularia-type andor argillic alteration are also typical Chloritization and phyllic alteration are strongly associated with the occurrence of Cu mineralization in the Baia Mare district Structural control association with magmatic intrusions the mineralogical composition of the ores and association with distinct types of hydrothermal al-teration are indicative of an adularia-sericite type (Heald et al 1987) ie low sulphidation epithermal system
Cremenea-Şuior
The polymetallic Şuior-Cremenea deposit is one of the most economically important within the Baia Mare dis-trict Structural control of the mineralization is particularly evident since the Cremenea vein system is positioned di-rectly on the E-W (Baia Sprie-Şuior) regional alignment The latter represents a shear zone (Popescu 1986) part of the major E-W Dragoş-Vodă fracture The Cremenea vein is in exact alignment with the extension of the Principal vein from Baia Sprie suggesting that the two belong to the same mineralised structure (Baia Sprie-Şuior metal-logenetic structure)
The Cremenea lsquoveinrsquo is an important ndash and in many ways exceptional ndash orebody in the Baia Mare district due to its size at upper levels the vein extends ca 800 m along strike reaching a depth of 1200 m with a width between 2 and 40 m The maximum width was at upper levels and was exploited by open pit ores were predominantly of Au-Ag type According to BORCOŞ et al (1973) calling the orebody a lsquoveinrsquo is inappropriate because the lsquoveinrsquo actually has a lens-like shape Berbeleac (1998) report-ed that the Cremenea vein contains gt 30 Mt ore Beneath the Au-Ag ores at upper levels base metal mineralization is predominant in middle and lower parts Telescoping is recognised in the middle part of the vein with Au-Ag mineralization overlapping the base metal ores The vein cavity contains explosion breccias made up of fragments of andesite and sedimentary rocks all highly silicifi ed sericitized and adularized This is also recognized in Baia Sprie veins supporting the unity of the Baia Sprie-Şuior structure
The Cremenea vein like the Principal vein in Baia Sprie lies on the northern side of a subvolcanic intrusion of porphyritic microdiorite which is considered to belong to the pyroxene-amphibole andesites (Jereapăn phase) The porphyry microdiorite intrudes sedimentary rocks of Paleogene Sarmatian and Pannonian age as well as Pan-nonian quartz-andesites and pyroxene andesites Accord-ing to their respective radiometric data the age of the in-trusion is considered to be Pontian by BORCOŞ et al (1973) and Pannonian by Edelstein et al (1992) The porphyry
microdiorite in Şuior is the eastern extension of the same dyke in Baia Sprie
Stanciu et al (1970) described adularization silici-fi cation and argillization as the most important types of hydrothermal alteration associated with Au-Ag ores in the upper part of the Cremenea vein
Brecciated textures are ubiquitous within the vein with heterogeneous fragments of sedimentary and erup-tive rocks cemented by quartz and sulphides In the upper part the predominant textures are lightly banded with a collomorphic aspect consisting of mm-scale opal chal-cedony quartz and sulphides In the lower part of the ore deposit where the mineralization has a predominantly base-metal character the texture is massive and banded The parallel banded character is expressed by an alter-nation of the different varieties of quartz and amorphous silica At upper levels there were also frequent geodes with quartz crystals Although transition from Au-Ag ore to base-metal ore is gradual the presence of a clear vertical zonation very similar to that at Baia Sprie can be observed with an upper Au-Ag-bearing part and a lower part enriched in base metals In comparison with Baia Sprie however Şuior lacks a clear cupriferous zone specifi c to lower levels with Cu distributed throughout the vertical extent of the deposit The upper Au-Ag part consists of pyrite wurtzite sphalerite arsenopyrite chal-copyrite tetrahedrite galena boulangerite and marcasite Below 800 m sphalerite and galena are predominant frequently associated with chalcopyrite Inclusions of Sb-sulphosalts (tetrahedrite proustite and pyrargyrite) appear frequently within galena Beneath the gold zone Cu-rich ores (pyrite-chalcopyriteplusmnarsenopyrite) may be present at the northern boundary of the orebody They may also in-clude Bi-minerals as described below In this zone the vein width is reduced to just 15ndash30 cm
Homogenisation temperature of two-phase fl uid inclu-sions in quartz varies between 230 and 280 ordmC (BORCOŞ et al 1973) Determination of fl uid inclusion homogenisa-tion temperatures was from quartz from upper and median levels As in all deposits of the Baia Mare area formation temperatures in the lower base-metal mineralization are believed to have been signifi cantly higher Similar conclu-sions were reached by Pomacircrleanu (1971)
According to BORCOŞ et al (1973) native gold has a sporadic presence Damian and Damian (1998) have identifi ed microscopic native gold in both Au-Ag ore and base metal ores In the upper Au-Ag part of the vein native gold is associated with quartz (80 ) and subordinately with pyrite and sphalerite In the base metal ores native gold is predominantly associated with sulphides (25 of gold in pyrite 34 in sphalerite 24 in galena 05 in arsenopyrite and 05 in tetrahedrite) and with quartz
Bi-sulphosalts at Şuior 203
(16 ) The fi neness of native gold is typically between 700 and 755
Description and microanalysis of the Bi-mineral assemblages
Methodology
Electron probe microanalytical data were collected us-ing a Cameca SX-51 instrument at Adelaide Microscopy Adelaide Australia Operating conditions were 20 kV ac-celerating voltage and 195 na beam current Standards used were as follows Bi2Se3 (Bi) PbS (Pb S) Ag (Ag) Cu (Cu) Sb2S3 (Sb) Te (Te) These data are supplemented by data collected using a Hitachi scanning electron micro-scope equipped with an Oxford Instruments wavelength-dispersive spectrometer at the Natural History Museum University of Oslo Blocks were polished to 01 microm using synthetic diamond compounds Electron probe micro-analyses are accurate to +- 2 relative standard Came-
ca-supplied data reduction packages and no matrix cor-rection coeffi cients were used following experience with similar material from other deposits Minimum detection limits are on the range of 003 wt for all elements all samples were carbon-coated prior to SEM study and mi-croprobe analysis
Description and results
The samples containing Bi-sulphosalts which were exam-ined in this study are located in the base metal mineraliza-tion of Cremenea vein (Fig 2) below level 750ndash800 m The Bi-sulphosalts occur however within a Cu-rich ore (pyrite-chalcopyrite assemblage) similar to that identi-fi ed at Toroiaga (Cook 1997 1998) Nistru (Damian amp Cook 1999 Damian et al 2000) and at Băiuţ-Văratic (Cook 1998 Damian et al 2000) In the Cremenea-Şuior orebody such association is found typically close to the northern contact of the vein with the intrusive host rock The gangue consists of quartz
Fig 2 NNW-SSE cross-section across the Şuior-Cremenea orebody with geological set-ting and location of specimens described in this study
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
202 G Damian et al
phyllic alteration in deposits with Au-enrichment at up-per levels adularia-type andor argillic alteration are also typical Chloritization and phyllic alteration are strongly associated with the occurrence of Cu mineralization in the Baia Mare district Structural control association with magmatic intrusions the mineralogical composition of the ores and association with distinct types of hydrothermal al-teration are indicative of an adularia-sericite type (Heald et al 1987) ie low sulphidation epithermal system
Cremenea-Şuior
The polymetallic Şuior-Cremenea deposit is one of the most economically important within the Baia Mare dis-trict Structural control of the mineralization is particularly evident since the Cremenea vein system is positioned di-rectly on the E-W (Baia Sprie-Şuior) regional alignment The latter represents a shear zone (Popescu 1986) part of the major E-W Dragoş-Vodă fracture The Cremenea vein is in exact alignment with the extension of the Principal vein from Baia Sprie suggesting that the two belong to the same mineralised structure (Baia Sprie-Şuior metal-logenetic structure)
The Cremenea lsquoveinrsquo is an important ndash and in many ways exceptional ndash orebody in the Baia Mare district due to its size at upper levels the vein extends ca 800 m along strike reaching a depth of 1200 m with a width between 2 and 40 m The maximum width was at upper levels and was exploited by open pit ores were predominantly of Au-Ag type According to BORCOŞ et al (1973) calling the orebody a lsquoveinrsquo is inappropriate because the lsquoveinrsquo actually has a lens-like shape Berbeleac (1998) report-ed that the Cremenea vein contains gt 30 Mt ore Beneath the Au-Ag ores at upper levels base metal mineralization is predominant in middle and lower parts Telescoping is recognised in the middle part of the vein with Au-Ag mineralization overlapping the base metal ores The vein cavity contains explosion breccias made up of fragments of andesite and sedimentary rocks all highly silicifi ed sericitized and adularized This is also recognized in Baia Sprie veins supporting the unity of the Baia Sprie-Şuior structure
The Cremenea vein like the Principal vein in Baia Sprie lies on the northern side of a subvolcanic intrusion of porphyritic microdiorite which is considered to belong to the pyroxene-amphibole andesites (Jereapăn phase) The porphyry microdiorite intrudes sedimentary rocks of Paleogene Sarmatian and Pannonian age as well as Pan-nonian quartz-andesites and pyroxene andesites Accord-ing to their respective radiometric data the age of the in-trusion is considered to be Pontian by BORCOŞ et al (1973) and Pannonian by Edelstein et al (1992) The porphyry
microdiorite in Şuior is the eastern extension of the same dyke in Baia Sprie
Stanciu et al (1970) described adularization silici-fi cation and argillization as the most important types of hydrothermal alteration associated with Au-Ag ores in the upper part of the Cremenea vein
Brecciated textures are ubiquitous within the vein with heterogeneous fragments of sedimentary and erup-tive rocks cemented by quartz and sulphides In the upper part the predominant textures are lightly banded with a collomorphic aspect consisting of mm-scale opal chal-cedony quartz and sulphides In the lower part of the ore deposit where the mineralization has a predominantly base-metal character the texture is massive and banded The parallel banded character is expressed by an alter-nation of the different varieties of quartz and amorphous silica At upper levels there were also frequent geodes with quartz crystals Although transition from Au-Ag ore to base-metal ore is gradual the presence of a clear vertical zonation very similar to that at Baia Sprie can be observed with an upper Au-Ag-bearing part and a lower part enriched in base metals In comparison with Baia Sprie however Şuior lacks a clear cupriferous zone specifi c to lower levels with Cu distributed throughout the vertical extent of the deposit The upper Au-Ag part consists of pyrite wurtzite sphalerite arsenopyrite chal-copyrite tetrahedrite galena boulangerite and marcasite Below 800 m sphalerite and galena are predominant frequently associated with chalcopyrite Inclusions of Sb-sulphosalts (tetrahedrite proustite and pyrargyrite) appear frequently within galena Beneath the gold zone Cu-rich ores (pyrite-chalcopyriteplusmnarsenopyrite) may be present at the northern boundary of the orebody They may also in-clude Bi-minerals as described below In this zone the vein width is reduced to just 15ndash30 cm
Homogenisation temperature of two-phase fl uid inclu-sions in quartz varies between 230 and 280 ordmC (BORCOŞ et al 1973) Determination of fl uid inclusion homogenisa-tion temperatures was from quartz from upper and median levels As in all deposits of the Baia Mare area formation temperatures in the lower base-metal mineralization are believed to have been signifi cantly higher Similar conclu-sions were reached by Pomacircrleanu (1971)
According to BORCOŞ et al (1973) native gold has a sporadic presence Damian and Damian (1998) have identifi ed microscopic native gold in both Au-Ag ore and base metal ores In the upper Au-Ag part of the vein native gold is associated with quartz (80 ) and subordinately with pyrite and sphalerite In the base metal ores native gold is predominantly associated with sulphides (25 of gold in pyrite 34 in sphalerite 24 in galena 05 in arsenopyrite and 05 in tetrahedrite) and with quartz
Bi-sulphosalts at Şuior 203
(16 ) The fi neness of native gold is typically between 700 and 755
Description and microanalysis of the Bi-mineral assemblages
Methodology
Electron probe microanalytical data were collected us-ing a Cameca SX-51 instrument at Adelaide Microscopy Adelaide Australia Operating conditions were 20 kV ac-celerating voltage and 195 na beam current Standards used were as follows Bi2Se3 (Bi) PbS (Pb S) Ag (Ag) Cu (Cu) Sb2S3 (Sb) Te (Te) These data are supplemented by data collected using a Hitachi scanning electron micro-scope equipped with an Oxford Instruments wavelength-dispersive spectrometer at the Natural History Museum University of Oslo Blocks were polished to 01 microm using synthetic diamond compounds Electron probe micro-analyses are accurate to +- 2 relative standard Came-
ca-supplied data reduction packages and no matrix cor-rection coeffi cients were used following experience with similar material from other deposits Minimum detection limits are on the range of 003 wt for all elements all samples were carbon-coated prior to SEM study and mi-croprobe analysis
Description and results
The samples containing Bi-sulphosalts which were exam-ined in this study are located in the base metal mineraliza-tion of Cremenea vein (Fig 2) below level 750ndash800 m The Bi-sulphosalts occur however within a Cu-rich ore (pyrite-chalcopyrite assemblage) similar to that identi-fi ed at Toroiaga (Cook 1997 1998) Nistru (Damian amp Cook 1999 Damian et al 2000) and at Băiuţ-Văratic (Cook 1998 Damian et al 2000) In the Cremenea-Şuior orebody such association is found typically close to the northern contact of the vein with the intrusive host rock The gangue consists of quartz
Fig 2 NNW-SSE cross-section across the Şuior-Cremenea orebody with geological set-ting and location of specimens described in this study
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 203
(16 ) The fi neness of native gold is typically between 700 and 755
Description and microanalysis of the Bi-mineral assemblages
Methodology
Electron probe microanalytical data were collected us-ing a Cameca SX-51 instrument at Adelaide Microscopy Adelaide Australia Operating conditions were 20 kV ac-celerating voltage and 195 na beam current Standards used were as follows Bi2Se3 (Bi) PbS (Pb S) Ag (Ag) Cu (Cu) Sb2S3 (Sb) Te (Te) These data are supplemented by data collected using a Hitachi scanning electron micro-scope equipped with an Oxford Instruments wavelength-dispersive spectrometer at the Natural History Museum University of Oslo Blocks were polished to 01 microm using synthetic diamond compounds Electron probe micro-analyses are accurate to +- 2 relative standard Came-
ca-supplied data reduction packages and no matrix cor-rection coeffi cients were used following experience with similar material from other deposits Minimum detection limits are on the range of 003 wt for all elements all samples were carbon-coated prior to SEM study and mi-croprobe analysis
Description and results
The samples containing Bi-sulphosalts which were exam-ined in this study are located in the base metal mineraliza-tion of Cremenea vein (Fig 2) below level 750ndash800 m The Bi-sulphosalts occur however within a Cu-rich ore (pyrite-chalcopyrite assemblage) similar to that identi-fi ed at Toroiaga (Cook 1997 1998) Nistru (Damian amp Cook 1999 Damian et al 2000) and at Băiuţ-Văratic (Cook 1998 Damian et al 2000) In the Cremenea-Şuior orebody such association is found typically close to the northern contact of the vein with the intrusive host rock The gangue consists of quartz
Fig 2 NNW-SSE cross-section across the Şuior-Cremenea orebody with geological set-ting and location of specimens described in this study
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
204 G Damian et al
Fig 3 Back-scattered electron images illustrating aspects of the occurrence of Bi-sulphosalts in Şuior (a) Bi-sulphosalts (white) located at grain boundaries between quartz (Qz) and pyrite (Py) as well as within the quartz (b) Typical association of Bi-sulphosalts with chalco-pyrite (Cp) (c) and (d) Bi-sulphosalts associated with brecciation in quartz (c) and pyrite (d) (e) Bi-sulphosalts occurring as well-formed lamellae within chalcopyrite (f) Bi-sulphosalt lamellae (arrowed) crossing mutual boundaries between quartz and chalcopyrite The ten-dency for Bi-sulphosalts to fi ll the dilational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can also be seen (g) Blebs of Bi-sulphosalts within chalcopyrite along the margins of the larger lamellae (Fig 3g) Tet tetrahedrite (h) Combination of lamellae and smaller lsquodropletsrsquo of Bi-sulphosalts within chalcopyrite Tet tetrahedrite Wit wittichenite Scale bars are 100 microm on all images except (f) 200 microm and (g) 10 microm
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 205
The Bi-sulphosalts appear as clustered elongated patches placed mostly at contacts between quartz and sul-phides They may also be located at grain boundaries in the quartz aggregates especially when pyrite is the only sulphide adjacent to the cluster (Fig 3a) Typically how-ever they are found in close association with chalcopyrite (Fig 3b) Smaller rounded blebs of Bi-sulphosalts sur-round the larger patches these protrude into the quartz or pyrite grains along brecciation trails (Fig 3c d) When in chalcopyrite they occur instead as well-shaped la-mellae (Fig 3e) Such lamellae may be oriented at 60deg angles to one another suggesting they follow cleavage planes within chalcopyrite Such lamellae can however cross mutual boundaries between quartz and chalcopyrite (Fig 3f) This indicates that the structural control of host chalcopyrite for contained inclusions does not necessar-ily indicate that the Bi-sulphosalts formed as a result of exsolution The tendency for Bi-sulphosalts to fi ll the di-lational spaces created during brecciation at the junctions between quartz grains and chalcopyrite can be seen in the same fi gure The Bi-sulphosalts form only diffuse fi elds and inclusions trails in the adjacent pyrite within the same assemblage In detail we see that blebs of Bi-sulphosalts can also occur within chalcopyrite along the margins of the larger lamellae (Fig 3g) The same combination of la-mellae and smaller droplet-like bodies of Bi-sulphosalts within chalcopyrite is seen also in Fig 3h suggesting that precipitation of these minerals was contemporaneous with brecciation The droplet-like appearance is reminis-cent of textures from other deposits which we have in-terpreted to have been deposited as melt (Ciobanu et al 2005b) We also note small idiomorphic grains of tetrahe-drite formed along the margin of Bi-sulphosalt lamellae Although larger and irregular masses of tetrahedrite may also be seen (Fig 3g h) this mineral is always restricted to an association with Bi-sulphosalts The observed car-ies texture between tetrahedrite and Bi-sulphosalts in the
lamellae is probably the result of local replacement and re-equilibration during crystallisation Such marginal re-actions are also seen in the formation of wittichenite at the boundary between some of the lamellae and chalcopyrite (Fig 3h)
With the exception of wittichenite the Bi-sulphosalts correspond to compounds that plot along the matildite-galena join (AgBiS2-PbS) in the Ag(+Cu)-Bi(+Sb)-Pb system However only a small number of the lamellae and blebs are fully homogenous (Fig 4a-c) most of them show microscopic intergrowths of two or more miner-als with either lamellar or basket-weave textures (Figs 5 and 6) The compositional clusters obtained by electron probe microanalysis of homogenous lamellae 2x and bleb 3x overlap with one another in an area of the (Ag+Cu)-(Bi+Sb)-Pb diagram between the ideal composition PbAgBiS3 (corresponding to no named mineral) and half way towards the tie line corresponding to the lillianite homologue NL = 9 (Table 1 Fig 4e) Microanalysis pro-fi les taken along and across the homogenous lamella 2x (Fig 4a) indicate that compositional homogeneity is maintained throughout the entire lamella Despite this we observe towards the margins of this lamella some thin separations of darker colour on the BSE images (Ag-rich-er) (Fig 4b) which were avoided when taking the com-positional profi les Such Ag-rich lamellar separations are more obvious in many of the other lamellae (eg Fig 4d) We also observe that some of these separations are further decomposed into two-phase intergrowths
The second group of lamellae within the samples dis-play such lamellar intergrowths (Fig 5a b) These inter-growths consist of a combination of fi ne and coarser la-mellae parallel to the long axis of the grain larger lamellae may also show basket-weave intergrowths between galena (bright on the BSE images) and matildite (dark) In indi-vidual patches the separation between the domains with basket-weave and lamellar intergrowths may be marked
Table 1 Electron probe microanalyses of PbAgBiS3 phase
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
206 G Damian et al
either by a curved (Fig 5c) or straight boundary (Fig 5d) Compositional plots for the parallel intergrowths (avoid-ing much of the basket-weave textures) show a spread be-tween the phases PbAgBiS3 and PbAg2Bi2S5 (Fig 7a) The data cluster expands on both sides of the galena-matildite join The plots represent various mixtures averaging the compositions across the two types of lamellae as shown in the detail in Fig 7b
The most abundant types of lamellae are those that display well-developed basket-weave intergrowths of galena and matildite (Fig 6) Needle-shaped matildite is generally coarser than the galena Within individual
patches we note distinct domains of basket-weave inter-growths with different orientations separated by curvilin-ear boundaries (Fig 6a) In detail the intergrowths with-in each domain show coarser and fi ner aspects (Fig 6b) In other patches the boundaries between domains with different orientations appear straight (Fig 6c) Although there is tendency towards parallel orientation of the intergrowths in such cases (Fig 6d) they nevertheless differ substantially from the fi ne parallel lamellar inter-growths described above One particular difference is in the needle-point termination of the matildite a feature characteristic for the galena-matildite basket-weave ex-
Fig 4 Back-scattered electron images illustrating aspects of the occurrence of homogeneous Bi-sul-phosalt lamellae from Şuior (a) lsquoLamella 2xrsquo (ideally PbAgBiS3) showing the typical 60ordm orientation with adjacent lamellae (b) Detail of lsquoLamella 2xrsquo in (a) showing marginal tetrahedrite (Tet) (c) lsquoGrain 4xrsquo (ideally PbAgBiS3) (d) lsquoLamella 10xrsquo a largely ho-mogeneous grain with tendency to develop internal parallel lamellar textures as well as decomposition along margins (e) Compositional data for PbAgBiS3 from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ter-nary diagram
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 207
Fig 5 Back-scattered electron images illus-trating aspects of the occurrence of Bi-sul-phosalts showing parallel lamellar textures from Şuior (a) and (b) Intergrowths consist of a combination of fi ne and coarser lamel-lae parallel to the long axis of the grain (c) and (d) Larger lamellae may also show basket-weave intergrowths between galena (bright) and matildite (dark) The bounda-ry between the domains with basket-weave and lamellar intergrowths may be either cur-ved (c) or straight (d)
Fig 6 Back-scattered electron images il-lustrating aspects of the occurrence of Bi-sulphosalts showing basket-weave textures from Şuior (a) Distinct domains of basket-weave intergrowths with different orienta-tions separated by curvilinear boundaries (b) Detail on intergrowths in (a) showing that within each domain there are coarser and fi ner aspects Note that needle-shaped matildite (dark) is generally coarser than the galena (c) Straight boundaries between do-mains with different orientations (d) Detail of basket-weave intergrowths in (c) show-ing a tendency towards parallel orientation Note however the needle-shaped termina-tion of matildite (dark) (e) Co-existence of basket-weave intergrowths of galena and matildite with homogenous domains of in-termediate compositions (f) Homogeneous areas of galena (bright) separated from the basket weave intergrowths
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
208 G Damian et al
solutions but not of the parallel lamellar intergrowths A further aspect of the patches with basket-weave inter-growths is that they typically coexist with homogenous domains within the same patch (Fig 6e) The composi-tional plot for patches with basket-weave intergrowths expands on both sides of the ideal phase PbAgBiS3 along the PbS-AgBiS2 join (Fig 8a) Close-to-galena compo-sitions were measured from larger homogeneous areas separated from the basket-weave intergrowths (brighter areas in the BSE images Fig 6f) close-to-matildite compositions are determined for the needle-shaped la-mellae in the same intergrowths (darker areas in the BSE images Fig 8b) There is thus a difference in the com-positional spread between the lamellar and basket-weave intergrowths on the one hand and the homogenous grains on the other Nonetheless they all are tied together to
the galena-matildite join and point to an ideal phase with composition PbAgBiS3
Discussion and conclusions
Galena-matidite series
The existence of intermediate phases between galena and matildite along the PbS-AgBiS2 join has not been proven in many of the experimental studies of the PbS-Ag2S-Bi2S3 system (eg Van Hook 1960 Craig 1967) Wang (1999) however reported no less than fi ve in-termediate phases in the system (in the range from 31 to 67 mol AgBiS2) forming at temperatures as low as 144 ordmC This latter study has shown that the interme-
Fig 7 (a) Compositional data for Bi-sulphosalts sho-wing parallel lamellar textures from Şuior plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (grains 10 13 14n and 15) (b) Typical aspect of the lamellar in-tergrowths in the analysed grains
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 209
diate solid-solution in the above compositional range is formed in the temperature interval 230ndash144 degC However the intermediate solid-solution remains continuous only down to 175 degC Below 175 degC it separates into 4 solvi from which the 5 discrete phases are crystallised below 144 degC (Fig 9) Final exsolution of matildite and galena may also occur at still lower temperatures from each of these phases The intermediate compositional range has a miscibility gap on both sides The gap on the PbS side (PbSss + PbS-AgBiS2 ss) is a two-phase fi eld between 85 to 29 AgBiS2 with solvus crest at 325 degC and 17 AgBiS2 The solvus on the matildite side (PbS-AgBiS2 ss
+ matildite) is asymmetrical and is placed between 67 AgBiS2 (PbAg2Bi2S5) at 190 degC and matildite at 144 degC The importance of these results can be seen in the fact that they predict formation of minerals with compositions
Fig 8 (a) Compositional data for Bi-sulphosalts displaying basket-weave intergrowths of galena and matildite plus homogeneous galena and matildite in grains 6 and 7x plotted in a (Bi+Sb) ndash (Ag+Cu) ndash Pb ternary diagram (b) Typical basket-weave intergrow-ths in grains from which composition of galena (Gn) and matildite (Mtd) were acquired (grey circles on a) The diamonds represent compositions of areas with fi ne basket-weave intergrowths
Fig 9 Simplifi ed depiction of the PbS - AgBiS2 phase diagram from Wang (1999) indicating the four solvi in the central portion of the diagram as dashed curves
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
210 G Damian et al
corresponding to the synthetic phases obtained from the intermediate solid solution range(s) even though the study does not provide specifi c stability conditions for any of them It is however apparent from the experi-ments that intermediate members may be eventually pre-served under geological conditions (much slower cool-ing paths than in the experiments) This contrasts with previously generalised opinion that only fi nal exsolution products ie galena and matildite will crystallise at low temperatures from PbS-AgBiS2 solid-solution at higher temperature
Intermediate members of the galena-matildite series in Şuior
Natural analogues of these phases including PbAg2Bi2S5 Pb4Ag56Bi56S152 and PbAgBiS3 have been noted from a number of vein occurrences eg Karamazar Rus-sia (Bortnikov et al 1987) Colorado California and Pennsylvania USA (Foord amp Shawe 1989) Štiavnica-Hodruša Slovakia (Kovalenker et al 1993) and most recently by the present authors (Ciobanu et al 2005a) from the Săcăricircmb deposit in Romania
In Şuior we observe that despite the widespread pres-ence of galena-matidite intergrowths homogenous do-mains of intermediate composition co-exist with such intergrowths (Fig 6f) Moreover whereas the basket-weave textures are highly indicative of exsolution (or de-composition) of a single phase at an immiscibility point the fi ne lamellar intergrowths (eg Fig 6b) are not The latter suggest that a composition which is slightly dif-ferent from that attained at an immiscibility point is ac-commodated by lattice-scale intergrowths of two or more intermediate phases that share structural elements (stack-ing disorder) This is well-known for other Bi-sulphosalt series (ie bismuthinite derivative series lillianite ho-mologous series Pring 1989 Pring et al 1999 Pring amp Ciobanu 2008) Coarsening of lattice-scale intergrowths to microscopic scale is also known for members of the cuprobismutite series and structurally-related paderaite (Ciobanu et al 2004) Co-existence of both lamellar and basket-weave intergrowths within the same patch sug-gests that locally some of the domains (Fig 5c) or lamel-lae (eg Fig 5d) reached compositions at immiscibility points
The spread of compositional data representing ei-ther homogenous areas or a mixture between such areas and fi ne basket-weave intergrowths is centred onto the PbAgBiS3 point with 50 AgBiS2 (Fig 8a) The cluster formed by individual points representing lamellar inter-growths is centred instead on the Pb4Ag56Bi56S152 phase
(Fig 6a) We also note that this cluster is not as well aligned along the galena-matildite join as the one repre-senting the basket-weave intergrowths and their associated homogenous areas This may be explained by the fact that a lamellar intergrowth is typically more inhomogeneous on the scale of the microprobe beam than the more regu-lar basket-weave The above results indicate that although both types of intergrowths represent compositions within the intermediate solid-solution range of the PbS-AgBiS2 series they are formed from distinct solvi domains The patches with dominant basket-weave intergrowths thus represent the phase PbAgBiS3 situated mid-way between Pb3Ag2Bi2S7 and Pb4Ag56Bi56S152 The patches with domi-nant lamellar intergrowths mainly represent the Ag-richer phase Pb4Ag56Bi56S152 situated between PbAgBiS3 and PbAg2Bi2S5
The data cluster obtained from the homogenous lamel-lae is located (as the centre the basket-weave cluster) at the position of the PbAgBiS3 phase along the PbS-Ag-BiS2 join although the cluster is shifted vertically towards slightly higher Bi values than those corresponding to this series (Fig 4e) This compositional expansion on only one side of the PbS-AgBiS2 join is unexpectedly seen only for those lamellae with almost complete homogenous appear-ance (with negligible fi nal breakdown to galena-matildite intergrowths) We suggest that such lamellae represent a compositional fi eld encompassing lattice-scale inter-growths between PbAgBiS3 and one of the Ag-bearing lillianite homologues Coherent lattice scale intergrowths can be formed between Bi-sulphosalts that are not mem-bers of the same series (polysomatic intergrowths) (eg lillianite and cosalite Pring amp Etchmann 2002 cupro-bismutite and paderaite Ciobanu et al 2004) However such a hypothesis needs to be proven by investigations at the lattice-scale using high resolution electron micro-scopy Alternatively the slight Bi excess may represent a limited solid-solution range in the mineral structure again this would need to be checked by single crystal investigations Whichever of these alternatives is cor-rect the slight Bi excess seems to stabilise formation of PbAgCuS3 since we see these lamellae alone are not decomposed into extensive intergrowths although this phase is compositionally overlapped in all types of lamel-lae within the occurrence
From the discussion above we conclude that the Bi-sulphosalts in the Şuior occurrence include at least two intermediate members of the galena-matildite series ie PbAgBiS3 and Pb4Ag56Bi56S152 as well as their fi nal de-composition products matildite and galena The existence of the second member is however based upon interpre-tation of the composition within patches with dominant lamellar intergrowths The compositional range of the
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Bi-sulphosalts at Şuior 211
patches that represent the entire occurrence is between 40ndash70 AgBiS2 thus corresponding to part of the in-termediate range of solid-solution in the galena-matildite series as given by Wang (1999) although with the most numerous group of lamellae formed at 50 AgBiS2
Since intergrowths of galena and matildite may give compositions resembling each of the intermediate mem-bers of the galena-matildite series careful study using scanning electron microscopy is essential to distinguish homogeneous phases from obvious mixtures The back-scattered electron images and compositional data in the present study demonstrate that a phase with the composi-tion PbAgBiS3 exists within the Şuior ores
Formation of Bi-sulphosalts in Şuior
The Bi-sulphosalts in Şuior were likely precipitated in a molten form as seen from the curvilinear boundaries be-tween distinct domains within many of the patches They represent the crystallisation products of several solvi formed below 175 degC from the larger solvus formed at temperatures below 230 degC as considered by Wang (1999) in the galena-matildite series Formation of intermediate members below 144 degC in different patches is partially preserved despite breakdown into galena and matildite intergrowths of many of these phases at even lower tem-peratures
Although formed at similar conditions the homog-enous lamellae averaging PbAgBiS3 have a slight Bi-ex-cess [(Ag081Cu012)093Pb091(Bi111Sb006)117(S298Se002)3] and are preserved as a unique phase suggesting that crystal-lisation in such cases was already frozen at 175 degC (before solvi formation) Thus although intermediate members of the series are formed at temperatures as low as 144 degC and end-members at temperatures even lower the min-eral relationships in Şuior corroborated with the phase diagram of Wang (1999) for the galena-matildite series allow us to conclude that minimum temperatures of pre-cipitation are between 230ndash175 degC However precipita-tion of the patches forming homogenous lamellae which do not show the solvi separation make the upper 230 degC estimate appear more realistic
Textures discussed in the present paper show that the Bi-sulphosalt assemblage in the Şuior occurrence is formed from precipitates fractionated in a molten form and from a fl uid involved during episodes of brecciation The intimate association of Bi-sulphosalts with tetra-hedrite within the majority of the patches indicates that these minerals are formed from the same Cu-rich fl uids that produced chalcopyrite Otherwise elements such as Sb involved in formation of tetrahedrite could be easily
incorporated as minor elements within the Bi-sulphosalts themselves Finally we note that the Bi-sulphosalt associ-ation in Şuior displays a very restricted mineral speciation in comparison with other occurrences of Bi-sulphosalts from Baia Mare district It shows nonetheless similarities in the association with Cu-rich ores that are also enriched in Au in some of these other occurrences (eg Toroiaga Cook 1997) In contrast with these occurrences howev-er where the Cu-Bi-Au association relates to hotter and also deeper (in some cases) levels of mineralization the Cu-Bi-sulphosalt association in Şuior is part of the upper levels with precipitation temperatures in the epithermal range
As in other epithermal vein systems in the Carpathi-ans and elsewhere where favourable conditions to form intermediate members of the galena-matildite series are met there is also a likelihood of precipitation in a molten state under such conditions Incorporation (lsquoscavengingrsquo) of Au in such Bi-based melts (which later crystallise as sulphosalts or tellurides) is currently recognised as an im-portant mechanism to concentrate gold and to explain the strong paragenetic association between gold and Bi-minerals in a variety of ore types Although scavenging of gold is an attractive mechanism in high-temperature (gt 400 degC) environments (eg skarns orogenic and meta-morphosed gold deposits) It has been argued based on phase equilibria (Ciobanu et al 2005b 2006) that the mechanism can also operate at the upper end of epither-mal conditions (240ndash300 degC) Our interpretation of the assemblages at Şuior suggests that it may in fact oper-ate even at relatively low temperatures The possibility of gold partitioning into the Bi-sulphosalts at Şuior will be the subject of further study
Acknowledgements
This paper is a contribution to International Geoscience Project 486 lsquoAu-Ag-Te-Se depositsrsquo CLC gratefully ac-knowledges receipt of an ARC Discovery fellowship The assistance of Angus Netting Peter Self and John Terlot (Adelaide Microscopy) with the analytical work is much appreciated
References
Bailly L Milesi J P Leroy J amp Marcoux E (1998) The AundashCundashZnndashSb epithermal mineralisations of the Baia Mare district (North Romania) new mineralogical and microthermo-metric results ndash Comptes Rendus de lrsquoAcadeacutemie des Sciences Series IIa Earth and Planetary Science 327 385ndash390
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
212 G Damian et al
Balintoni I (1997) Geotectonica terenurilor metamorfi ce din Romacircnia ndash Ed Carpatica Cluj-Napoca 176 pp
Berbeleac I (1998) Zăcăminte de plumb şi zinc ndash Ed Tehnică Bucureşti 528 pp
Biruk S V amp Skakun L Z (2000) Bismuth minerals of the Be-regovo ore fi eld mineral assemblages and spatial zonation (Tran-scarpathian Ukraine) ndash Geol Quarterly 44 (1) 39ndash46
BORCOŞ M (1994) Neogene volcanicitymetallogeny in the Oaş-Gutacirci Mts ndash In BORCOŞ M amp VLAD Ş (eds) IGCP 356 Field Trip Guide Plate tectonics and metallogeny in the East Carpathi-ans and Apuseni Mts Bucharest 20ndash22
BORCOŞ M LANG B BOŞTINESCU S MIcircNDROIU V amp VOLANSCHI E (1973) Consideraţii privind activitatea metalogenetică asociată andezitelor piroxenice ponţiene din munţii Gutacirci (Zăcămintele Herja Baia Sprie şi Şuior) ndash St Teh Econ Inst Geol (Bucureşti) Seria I nr 9 95ndash135
Bortnikov N S Laputina I P amp Safonov Y G (1987) New mineral group of the system Ag-Pb-Bi-S from Kanimansur ore fi eld Karamazar ndash Dokl Akad Sci USSR Earth Sci Sect 292 1459ndash1463
Ciobanu C L Pring A amp Cook N J (2004) Micron- to nano-scale intergrowths among members of the cuprobismutite series
and paderaite HRTEM and microanalytical evidence ndash Mineral Mag 68 279ndash300
Ciobanu C L Cook N J Capraru N Damian Gh amp Cri-stea P (2005a) Mineral assemblages from the vein salband at Sacarimb Golden Quadrilateral Romania I Sulphosalts ndash Geo-chem Miner Petrol (Bulg Acad of Sci Sofi a) 43 47ndash55
Ciobanu C L Cook N J amp Pring A (2005b) Bismuth tel-lurides as gold scavengers ndash In Mao J W amp Bierlein F P (eds) Mineral Deposit Research Meeting the Global Challenge Springer Berlin Heidelberg New York 1383ndash1386
Ciobanu C L Cook N J Damian F amp Damian G (2006) Gold scavenged by bismuth melts An example from Alpine shear-remobilisates in the Highiş Massif Romania ndash Mineral Petrol 87 351ndash384
Cook N J (1997) Bismuth and bismuth-antimony sulphosalts from Neogene vein mineralization Baia Borşa area Maramureş Romania ndash Mineral Mag 61 387ndash409
ndash (1998) Bismuth sulphosalts from hydrothermal vein deposits of Neogene age NW Romania ndash Mitt Oumlsterr Mineral Gesellsch 143 19ndash39
Cook N J amp Ciobanu C L (2004) Bismuth tellurides and sul-phosalts from the Larga hydrothermal system Metaliferi Mts Romania Paragenesis and genetic signifi cance ndash Mineral Mag 68 301ndash321
Cook N J amp Ciobanu C L Damian Gh amp Damian F (2004) Tellurides and sulphosalts from deposits in the Golden Quadrilat-eral ndash In Cook N J amp Ciobanu C L (eds) Gold-Silver-Tel-luride Deposits of the Golden Quadrilateral South Apuseni Mts Romania ndash Guidebook Internat Field Workshop of IGCP-486 Alba Iulia Romania 31st Aug ndash 7th Sept 2004 IAGOD Guide-book Series 12 111ndash144
Craig J R (1967) Phase relations and mineral assemblages in the Ag-Bi-Pb-S system ndash Miner Deposita 1 278ndash306
Damian F (1995) Intruziunea micromonzodioritică din cacircmpul metalogenetic Nistru Buletinul Ştiinţific al Universităţii din Baia Mare Seria D Exploatări miniere Prepararea substanţelor mine-rale utile Metalurgie neferoasă ndash Geologie şi Ingineria mediului Vol IX 51ndash58
Damian F amp Cook N J (1999) Bi-sulphosalts from the cuprifer-ous mineralisations fromnistru Baia Mare area ndash Rom J Min-eral 79 (suppl nr 1) 27
Damian F Damian Gh amp Costin D (2000) Bismuth sulphos-alts in the Neogene hydrothermal vein ores from the Baia Mare Ore District ndash Acta Mineralogica-Petrografi ca Szeged XLI (suppl) 27
Damian Gh amp Costin D (1999) New data about the bismuth sulphosalts from the hydrothermal mineralisations from Văratic-Băiuţ Baia Mare district Rom J Mineral 79 (supplement nr 1) 28
Damian Gh amp Damian F (1998) Les parageneses de lrsquoor natif dans le fi lon de Cremenea le gisement de Şuior la region de Baia Mare ndash Buletinul Ştiinţific al Universităţii din Baia Mare Se-ria D Exploatări miniere Prepararea substanţelor minerale utile Metalurgie neferoasă Geologie şi Ingineria mediului Vol XII 105ndash112
Damian Gh Damian F amp Istvan D (2003) The Neogene met-allogenesis of the central western area of the Baia Mare District (Gutacirci Mts ndash East Carpathians) Final GEODE-ABCD Work-shop Geodynamics and Ore Deposit Evolution of the Alpine-Balkan-Carpathian-Dinaride Province Seggauberg Austria 22ndash24 March 2003 Abstract vol 26
Edelstein O Bernad A Kovacs M Crihan M amp Pecskay Z (1992) Preliminary date regarding the K-Ar ages of some eruptive rocks from Baia Mare Neogene volcanic zone ndash Reacutev Roum Geacuteol Geacuteophys Geacuteogr Geacuteologie 36 45ndash60
Finalyi I amp Koch S (1929) Fuumlloumlppite a new Hungarian Mi-neral of the plagionite-semseyite group ndash Mineral Mag 22 179ndash189
Foord E E amp Shawe D R (1989) The Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulphosalts A review and some new data from Colorado California and Pennsylvania ndash Can Mineral 27 363ndash382
GIUŞCĂ D BORCOŞ M Lang B amp Stan N (1973) Neogene volcanism and metallogenesis in the Gutacirci Mountains ndash Guide Excursion IGR Bucharest
Grancea L Bailly L Leroy J L Banks D Marcoux E Mileacutesi J P Cuney M Andreacute A S Istvan D amp Fabre C (2002) Fluid evolution in the Baia Mare epithermal goldpolymetallic district Inner Carpathians Romania ndash Mineral Deposita 37 630ndash647
Heald P Foley N K amp Hayba D O (1987) Comparative anatomy of volcanic-hosted epithermal deposits acide-sulfate and adularia-sericite type ndash Econ Geol 82 3ndash26
JELEŇ S Haber M amp Kodera P (2000) New results on ore min-eralization in the Štiavnica-Hodruša ore district Slovacia ndash Acta Mineral-Petrograf Szeged XLI (suppl) 59
Kenngott A (1853) Mineralogische Notizen Sitzungsber der Akad d Wissensch Wien Bd 10 288ndash299
Kovacs M Grancea L IŞTVAN D Nedelcu L Mihalache A amp CHIUZBĂIAN C (2001) Baia Sprie epithermal deposit ndash Rom J Mineral Deposits 79 9ndash12
Kovalenker V A JELEŇ S amp Sandomirskaya S (1993) Min-erals of the system Ag-Cu-Pb-Bi-S from polymetalic viens of the Štiavnica-Hodruša ore fi eld (Slovakia) ndash Geol Carpath 44 409ndash419
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
Lang B Edelstein O Kovacs M Bernad A amp Crihan M (1994) K-Ar age determination on Neogene Volcanic rocks from Gutacirci Mts (eastern Carpathians Romania) ndash Geol Carpath 45 357ndash363
Matkovsky O I Remeshilo B G Yasinskaya A A Shkly-anka V M amp Yerzeva L N (1987) The new fi nds of bismuth minerals from Transcarpathian (in Russian) ndash Miner Zhurn 3 (9) 79ndash86
Neubauer F Lips A Kouzmanov K Lexa J amp IVĂŞCANU P (2005) 1 Subduction slab detachment and mineralization the Neogene in the Apuseni Mountains and Carpathians ndash Ore Geol Rev 27 13ndash44
Peacutecskay Z Edelstein O Seghedi I Szakaacutecs A Lexa J Kovacs M Crihan M amp Bernard A (1995a) KndashAr datings of NeogenendashQuaternary calc-alkaline volcanic rocks in Roma-nia ndash Acta Vulcanologica 7 53ndash61
Peacutecskay Z Lexa J Szkaacutecs A Balogh K Seghedi I KONEČNY V Kovacs M Maacuterton E Kaliciak M Szeacuteky-Fux V Poacuteka T Gyarmati P Edelstein O ROŞU E amp Zec B (1995b) Space and time distribution of NeogenendashQuaternary volcanism in the Carpatho-Pannonian Region ndash Acta Vulcanolo-gica 7 15ndash28
Pomacircrleanu V (1971) Geotermometria şi aplicarea ei la unele minerale din Romacircnia ndash Ed Academiei Romacircne Bucureşti 158 p
Popescu C Gh (1986) Metalogenie aplicată şi prognoza geo-logică ndash Edit Univ Bucureşti 316 p
ndash (1994) A Geodinamic Model regarding the Neogene Volcanism and the associated Metallogenesis in Baia Mare Metallogenetic District (The East Carpathians) ndash Analele Univ Bucureşti Seria Geol XLIII 19ndash26
Pring A (1989) Structural disorder in aikinite and krupkaite ndash Amer Mineral 74 250ndash255
Pring A amp Ciobanu C L (2008) Chemical modulations in PbndashBi sulphosalts a glimpse at minerals in solid-state chemistry In Harris K amp Edwards P (eds) Turning points in Solid State Materials and Surface Chemistry Roy Soc Chem Publ 239ndash249
Pring A amp Etchmann B (2002) HRTEM observations of struc-tural and chemical modulations in cosalite and its relationship to the lillianite homologues ndash Mineral Mag 66 451ndash458
Pring A Jercher M amp Makovicky E (1999) Disorder and compositional variation in the lillianite homologous series ndash Mineral Mag 63 917ndash926
Remeshilo B G Yasinskaya A A amp Matkovsky O I (1989) The chemical composition of some sulphides from Beregovo ore deposit Transcarpathian (in Russian) ndash Miner Sbor Lvov 3 (2) 97ndash101
SĂNDULESCU M (1984) Geotectonica Romacircniei ndash Ed Tehnică Bucureşti 335 pp
ŞEGHEDI I DOWNES H SZAKAacuteCS A MASON R D P THIRLWALL F M ROŞU E Peacutecskay Z Maacuterton E amp Panaiotu C (2004) Neogene-Quaternary magmatism and geodynamics in the Car-tathian region a synthesis ndash Lithos 72 117ndash146
Socolescu M Bonea L amp Haiduc P (1963) Contribuţii la cunoasterea mineralizaţiei cuprifere de la Picircricircul lui Avram (M Apuseni) ndash Revista Minelor 14 9
Stanciu C Udrescu C amp MEDEŞAN A (1970) Studiul proce-sului de adularizare a andezitelor neogene din zăcămintele Şuior şi Nistru (M Gutacirci) St Teh Econ Inst Geol (Bucureşti) Seria A 8 27ndash51
Szoumlke A amp Steclaci L (1962) Regiunea Toroiaga Baia Borşa Studiul geologic petrografic şi geochimic ndash Ed Acad Romacircne Bucureşti 240 pp
Van Hook H J (1960) The ternary system Ag2S-Bi2S3-PbS ndash Econ Geol 55 759ndash788
Wang N (1999) An experimental study of some solid solutions in the system Ag2S-PbS-Bi2S3 at low temperatures ndash N Jb Miner Mh 1999 223ndash240
Received January 2006 accepted 2006 publisher received manuscript June 12 2008Responsible editor G C Ulmer
Authorrsquos addresses
Gh Damian Universitatea de Nord Str Victor Babeş 62A RO-4800 Baia Mare Romania
C L Ciobanu Department of Earth and Environmental Sciences University of Adelaide SA 5005 Australia and Department of Min-eralogy South Australian Museum North Terrace Adelaide SA 5000 Australia
N J Cook Natural History Museum University of Oslo Boks 1172 Blindern NO-0318 Oslo Norway
F Damian Universitatea de Nord Str Victor Babes 62A RO-4800 Baia Mare Romania
