ORIGINAL PAPER

Mineralogical, stable isotope, and fluid inclusion studiesof spatially related porphyry Cu and epithermal Au-Temineralization, Fakos Peninsula, Limnos Island, Greece

Andrew P. Fornadel & Panagiotis Ch. Voudouris &Paul G. Spry & Vasilios Melfos

Received: 2 February 2011 /Accepted: 26 March 2012 /Published online: 17 April 2012# Springer-Verlag 2012

Abstract The Fakos porphyry Cu and epithermal Au-Tedeposit, Limnos Island, Greece, is hosted in a ~20 Ma quartzmonzonite and shoshonitic subvolcanic rocks that intrudedmiddle Eocene to lower Miocene sedimentary basementrocks. Metallic mineralization formed in three stages inquartz and quartz-calcite veins. Early porphyry-style(Stage 1) metallic minerals consist of pyrite, chalcopyrite,galena, bornite, sphalerite, molybdenite, and iron oxides,which are surrounded by halos of potassic and propyliticalteration. Stage 2 mineralization is composed mostly ofquartz-tourmaline veins associated with sericitic alterationand disseminated pyrite and molybdenite, whereas Stage 3,epithermal-style mineralization is characterized by polyme-tallic veins containing pyrite, chalcopyrite, sphalerite, gale-na, enargite, bournonite, tetrahedrite-tennantite, hessite,petzite, altaite, an unknown cervelleite-like Ag-telluride,native Au, and Au-Ag alloy. Stage 3 veins are spatiallyassociated with sericitic and argillic alteration. Fluid inclu-sions in quartz from Stage 1 (porphyry-style) mineralizationcontain five types of inclusions. Type I, liquidvapor inclu-sions, which homogenize at temperatures ranging from

189.5C to 403.3C have salinities of 14.8 to 19.9 wt. %NaCl equiv. Type II, liquidvapor-NaCl, Type III liquidvapor-NaCl-XCl2 (where XCl is an unknown chloridephase, likely CaCl2), and Type IV, liquidvapor-hematiteNaCl homogenize to the liquid phase by liquidvapor ho-mogenization or by daughter crystal dissolution at temper-atures of 209.3 to 740.5 C, 267.6 to 780.8 C, and 357.9 to684.2 C, respectively, and, Type V, vapor-rich inclusions.Stage 2 veins are devoid of interpretable fluid inclusions.Quartz from Stage 3 (epithermal-style) veins contains twotypes of fluid inclusions, Type I, liquidvapor inclusionsthat homogenize to the liquid phase (191.6 to 310.0 C)with salinities of 1.40 to 9.73 wt. % NaCl equiv., and TypeII, vapor-rich inclusions. Mixing of magmatic fluids withmeteoric water in the epithermal environment is responsiblefor the dilution of the ore fluids that formed Stage 3 veins.Eutectic melting temperatures of 35.4 to 24.3 C for TypeI inclusions hosted in both porphyry- and epithermal-styleveins suggest the presence of CaCl2, MgCl2, and/or FeCl2 inthe magmatic-hydrothermal fluids. Sulfur isotope values ofpyrite, galena, sphalerite, and molybdenite range from34S06.82 to 0.82 per mil and overlap for porphyry andepithermal sulfides, which suggests a common sulfur sourcefor the two styles of mineralization. The source of sulfur inthe system was likely the Fakos quartz monzonite for whichthe isotopically light sulfur isotope values are the result ofchanges in oxidation state during sulfide deposition (i.e.,boiling) and/or disproportionation of sulfur-rich magmaticvolatiles upon cooling. It is less likely that sulfur in thesulfides was derived from the reduction of seawater sulfateor leaching of sulfides from sedimentary rocks given theabsence of primary sulfides in sedimentary rocks in thevicinity of the deposit. Late-stage barite (34S010.5 permil) is inferred to have formed during mixing of seawaterwith magmatic ore fluids. Petrological, mineralogical, fluid

Editorial handling: R. Abart

A. P. Fornadel (*) : P. G. SpryDepartment of Geological and Atmospheric Sciences,253 Science I, Iowa State University,Ames, IA 50011-3212, USAe-mail: fornadel@iastate.edu

P. C. VoudourisDepartment of Mineralogy-Petrology, University of Athens,Athens 15784, Greece

V. MelfosDepartment of Mineralogy, Petrology and Economic Geology,Aristotle University of Thessaloniki,Thessaloniki 54124, Greece

Miner Petrol (2012) 105:85111DOI 10.1007/s00710-012-0196-8

inclusion, and sulfur isotope data indicate that the metallicmineralization at Fakos Peninsula represents an early por-phyry system that is transitional to a later high- to intermediate-sulfidation epithermal gold system. This style of mineralizationis similar to porphyry-epithermal metallic mineralizationfound elsewhere in northeastern Greece (e.g., PagoniRachi, St. Demetrios, St. Barbara, Perama Hill, Mavrokoryfi,and Pefka).

Introduction

Porphyry- and epithermal-style metallic ore deposits arefound worldwide and are related to the generation of hy-drous calc-alkaline and alkaline magmas in convergent tec-tonic regimes (e.g., Seedorff et al. 2005; Simmons et al.2005). Despite being geologically distinct, these two typesof ore deposit share a common elemental metal assemblagethat includes Au, Cu, and S, and they constitute majorglobal resources of both precious and base metals. Thetwo styles of deposit are commonly spatially and temporallyrelated to one another (Arribas 1995; Heinrich et al. 2004).However, epithermal style mineralization invariably transi-tions to porphyry style mineralization at depth (Sillitoe1994; Heinrich 2005).

In areas where these two deposit types are spatiallyrelated, Heinrich (2005) suggested that the epithermal-stylemineralization formed contemporaneously with porphyry-style mineralization, within the error of age-dating techni-ques (e.g., Far South East - Lepanto, Arribas 1995), or that itmay post-date porphyry mineralization by >1 Ma (e.g.,Colquijirca district, Bendezu et al. 2003).

Post-orogenic extension and subsequent magmatism innortheastern Greece and the northern Aegean Sea havegiven rise to a broad variety of styles of hydrothermalmineralization, which include Pb-Zn-Ag veins, metamor-phic base metal replacement, sediment-hosted gold, low-to high-sulfidation epithermal gold, intrusion-related gold,and porphyry CuMoAu deposits (e.g., Melfos et al.2002; Marchev et al. 2005; Voudouris 2006; Fornadel etal. 2011). Also documented in the region are deposits, someof economic importance, which contain both epithermal-and porphyry-style mineralization (e.g., Kassiteres-Sappesarea with ~1.5 million tons of Au at grades of up to 18.4 g/t;Voudouris 2006).

Porphyry- and epithermal-style mineralization occurs inassociation with Miocene volcanism in the northern AegeanSea, particularly on the islands of Limnos and Lesbos(Voudouris and Skarpelis 1998; Voudouris and Alfieris2005; Voudouris et al. 2007a, b). Voudouris and Skarpelis(1998) and Voudouris and Alfieris (2005) reported Cu-Au(Mo)-bearing porphyry-style mineralization on FakosPeninsula, Limnos Island, that is spatially related to

epithermal-style Au-Te bearing veins. Although grade andtonnage information is unknown for this prospect, bulk rockmetal contents were measured in both an exploration effortby Argosy Mining (http://www.thefreelibrary.com/Argosy+Mining++Precious+Metals+Program+Extended+into+Greece.-a019029624) and a study by Voudouris andAlfieris (2005). Samples from these two studies contain upto 13 ppm Au, 11.3 ppm Ag, 780 ppm Cu, 3500 ppm Pb,256 ppm Zn, 300 ppm Sb, 26 ppm Bi, 4630 ppm As,83 ppm Mo, and 18 ppm Se. The Argosy Mining study alsonoted As-Sb-Au soil and rock anomalies, as well as Auanomalies in the sediments of intermittent streams that drainthe peninsula.

Voudouris and Alfieris (2005) suggested that the metallicmineralization on Fakos Peninsula, herein called the Fakosprospect, may define the southern-most extent of theOligocene to Miocene Serbomacedonian-Rhodope metallo-genic belt, which hosts porphyry- and epithermal-style min-eralization, and is part of the Alpine-Balkan-Carpathian-Dinaride metallogenetic and geodynamic province (Heinrichand Neubauer 2002; Marchev et al. 2005).

The purpose of this contribution is to evaluate the geol-ogy, mineralogy, and geochemistry (petrochemistry, sulfurisotope, and fluid inclusion studies) of the Fakos prospectby expanding upon the mineralogical and petrological stud-ies of Voudouris and Skarpelis (1998), Voudouris andAlfieris (2005) and Pe-Piper et al. (2009). The source ofsulfur to the mineralizing system and the physicochemicalconditions of ore formation, and microthermometric meas-urements of fluid inclusions trapped in quartz veins fromboth styles of mineralization elucidate changes in the phys-icochemical conditions during the formation of metallicmineralization as the environment transitioned from adeeper porphyry regime to a shallower epithermal setting.

Geologic setting

Regional geologic setting

In Greece and the northern Aegean Sea, the Hellenideorogen is a discrete terrane of the Alpine-Himalaya defor-mational belt and represents a geotectonic link between thesouthern Balkan Peninsula and Turkey. It formed as a resultof the ongoing Alpine collision between the African andEurasian plates since the Mesozoic and caused thrusting andnappe-stacking of three continental blocks (Apulia, Pelagonia,and Rhodope), as well as the intervening oceanic crust (Pe-Piper and Piper 2002; Pe-Piper et al. 2009) (Fig. 1).Subduction and duplexing of crust in the region occurredalong a north-dipping subduction front and the last twohigh-pressure metamorphic events during collision and crustalthickening have been dated at 51 and 42 Ma (e.g., Krohe and

86 A.P. Fornadel et al.

Mposkos 2001; Kilias et al. 2002; Marchev et al. 2005; Brunand Sokoutis 2007).

Since the late Tertiary, the Alpine subduction front mi-grated southwards where it forms the modern Hellenic vol-canic arc (Marchev et al. 2005). The retreat of thesubduction front gave rise to ongoing, large-scale regionalextension within the nappe stack, which occurs in and alongductile shear and detachment zones and, in a brittle manner,along normal faults. The continental crust in northeasternGreece has dilated ~100 % since the early Miocene and isone of the most rapidly extending regions in the world (e.g.,Dinter 1998; Pe-Piper and Piper 2002). The coupled migra-tion of the subduction front and large-scale regional exten-sion caused orogenic collapse and crustal thinning, as wellas the exhumation of deep-crustal metamorphic core com-plexes (Dinter and Royden 1993; Kilias et al. 2002).

The geology of northeastern Greece and the northernAegean Sea is characterized by widespread late Mesozoicto mid-Cenozoic igneous activity within thrusted crustalblocks that was caused by subduction-related processesassociated with the Alpine orogeny and has been ongoing

since the Mesozoic (Pe-Piper and Piper 2002). Igneousrocks of Mesozoic to Paleogene age are present in theRhodope block; however, similar rocks are notably absentin the Apulia and Pelagonia blocks (Pe-Piper et al. 2009).Eocene to Oligocene igneous activity occurred in theRhodope block and in northwestern Turkey and is dominatedby the intrusion of calc-alkaline, I-type granitoids into thetectonically-thickened crust and spatially associated withcalc-alkaline to shoshonitic volcanic rocks (Fig. 1) (Pe-Piperand Piper 2002; Dilek and Altunkaynak 2007; Pe-Piper et al.2009).

Early Miocene volcanism in the northeastern Aegean Seaand western Turkey occurred to the south of the Mesozoic toearly Cenozoic igneous activity of the Rhodope block andwas coeval with large-scale regional extension (Dinter 1998;Pe-Piper and Piper 2002; Pe-Piper et al. 2009). The igneousrocks associated with the Early Miocene have been definedas a belt of shoshonitic volcanic rocks (Pe-Piper and Piper2002; Pe-Piper et al. 2009) (Fig. 1). They originated fromlarge stratovolcanoes in the northeastern Aegean Sea, theremnants of which are present on the Greek islands of

++

+

+++

+++

+

+

+

+

AFRICAN PLATE

EURASIAN PLATEVardar suture

Pindos suture

Intra-Pontidesuture

I-Asuture

Black Sea

Hellenicsubduction

zonem

odernsubduction fron

t

Rhodope blockPelagonia blockApulia block

Neogeneaccretionary

prism

Aegean Sea

E 03E 02

32 N

36 N

40 N

+ Aegean shoshonite beltand volcanic centers

Surface traces of Mesozoicocean sutures

Cities

Limnos

Lesbos

Samothraki

Istanbul

N2000 km

Alexandroupolis

+++

+++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++

+++++++++++++++++

+++++++++++++++++++++++++++++++++

++++++++++++++++++++

AFRICAN PLATAA E

EURASIAN PLATAA EVardar sutureVV

Pindos suture

Intra-Pontidesuture

I-Asuture

Black Sea

Hellenicsubduction

zonem

odernsubduction fron

t

Rhodope blockPelagonia blockApulia block

Neogeneaccretionary

prism

Aegean Sea

E03E02

32 N

36 N

40 N

+++++++++++++++++++++ Aegean shoshonite beltand volcanic centers

Surface traces of Mesozoicocean sutures

Cities

Limnossssssssssssssssss

LesbLesbLesbLesbesLesLesbLesbLesbLesbLeLLesLesbesbesbLesbLesbesbLesbLes ososososososossosososssosososso

Samoooooooooooooooothrahthrathrathrahrathrathrathrathrathrathrathratthrahhrathrarathrarakikkkikkkikkkkikkkkk

Istanbul

N2000 km

Alexandroupolis

+ +++

+

+++

+++

++

++

Fig. 1 Regional geologicalmap of Greece and the AegeanSea showing the distribution ofshoshonitic volcanic rocks inthe northern Aegean Sea, suturezones, and the modern andHellenic subduction fronts.Modified from Pe-Piper andPiper (2002), Pe-Piper et al.(2009)

Fakos transitional porphyry Cu to epithermal Au-Te mineralization 87

Lesbos, Limnos, and Samothraki, and in western Turkey(Pe-Piper and Piper 2002; Altunkaynak and Dilek 2006;Pe-Piper et al. 2009).

Several possible causes for such widespread volcanic andplutonic activity have been proposed, however the mostwidely-accepted include steepened geothermal gradients as-sociated with mantle upwelling that was caused by thedetachment and/or roll-back of the subducting slab (e.g.,Fytikas et al. 1984; de Boorder et al. 1998; Pe-Piper et al.1998; Kilias and Mountrakis 1998; Melfos et al. 2002), andas crustal thickening due to subduction (e.g., Yilmaz 1990).Due to the style of rare earth element (REE) enrichment,Mg- and Cr-rich clinopyroxene phenocrysts, and an evolvedSm-Nd isotope signature for the rocks on Limnos Island, Pe-Piper et al. (2009) suggested that magmas in the regionincorporated upwelling asthenospheric mantle due to slabdetachment, which, in turn, caused melting of metabasalticamphibolites that underplated subducted continental crust.

Geology of Limnos Island

Limnos Island is predominantly comprised of Paleogeneflysch that was deposited in a NE-SW trending postorogenicbasin that formed as a result of normal faulting and exten-sion during postorgenic collapse of the Rhodope-Sakaryaorogen and comprises the sedimentary basement (Fig. 2).

The sedimentary rocks were slightly folded due to regionalcompression prior to the onset of large-scale regional exten-sion and associated igneous activity (Roussos et al. 1993;Innocenti et al. 1994; Tranos 2009; Brun and Sokoutis 2010)

According to Roussos et al. (1993), the sedimentarybasement rocks can be delineated into two discrete units,the Upper Unit and the Lower Unit. The late Eocene to earlyOligocene Lower Unit covers large parts of the island and iscomposed of siliciclastic continental slope deposits includ-ing conglomerates, sandstones, mudstones, claystones, andturbidites (Fig. 2). The early Oligocene Upper Unit is spa-tially more restricted than the Lower Unit and is interpretedto have been deposited in a shallower environment than theLower Unit. The Upper Unit is composed of marine andbrackish fluviodeltaic sedimentary rocks, including inter-bedded claystones and sandstones, sandstones, and sandylimestones at the bottom of the section. Towards its top, theUpper Unit is composed of terrestrial fluvial sediments,including conglomerates and sandstones.

Roughly half of the sedimentary basement on LimnosIsland is unconformably overlain by Lower Miocene volca-nic rocks of the Hellenide orogen, which consist of subvol-canic intrusions, lava flows, and pyroclastic deposits(Fytikas et al. 1980; Innocenti et al. 1994; Pe-Piper andPiper 2002; Pe-Piper et al. 2009). The volcanic centers arelocated in the western and southwestern portions of Limnos

Th Moudros

Katalakon

Myrina

Fakos Peninsula

L. Aliki

AgiosIoannis

Kaminia

RomanouL. Chortarolimni

TownsNLakes

Katalakon Unit: Fakos quartz monzonite

Paleogene SedimentaryBasement

"Therma Unit": Marls and Pyroclastics

Katalakon Unit: Subvolcanic Intrusions

Romanou Unit: Pyroclastics

Myrina Unit: Lava Domes

Agios IoannisSubunit

Th

40 km

40N

3956' N

3952' N

3948' N

22 14' E E '2222E '0122

Area of Study

Fig. 2 Geological map of Limnos Island modified from Innocenti et al. (1994) and Pe-Piper et al. (2009)

88 A.P. Fornadel et al.

Island, and are delineated by domes and lava flows that areaccompanied by agglomerates. The sedimentary basement isincreasingly exposed at the surface in the east and northeastof the island, distal to the volcanic centers (Fig. 2).

The volcanic rocks are divided into three units (Katalakon,Romanou, and Myrina) on the basis of lithology, age, andgeographic location (Innocenti et al. 1994). These rocks areLower Miocene in age (2118 Ma) and demonstrate a calc-alkaline to shoshonitic affinity (Fytikas et al. 1980, 1984;Innocenti et al. 1994; Pe-Piper and Piper 2002; Pe-Piper etal. 2009).

The lower-most Katalakon unit consists of NW trendingK-rich andesitic to dacitic lavas. In places, it is interbeddedwith, or crosscut by, andesitic lava flows, hydrothermalbreccias cemented by a monomineralic quartz matrix, sills,and E-W trending dikes (Innocenti et al. 1994; Pe-Piper andPiper 2002). Andesite and dacite in the Katalakon unityielded whole rock and groundmass K-Ar ages rangingfrom 21.30.7 to 20.20.2 Ma (Innocenti et al. 1994).This unit is overlain by the Romanou unit that is composedlargely of K-rich dacites and latites. At its base, theRomanou unit is dominated by light-colored lithic- andpumice-rich pyroclastic flows that are up to 160 m thick. Tothe west and up section, the pyroclastic flows of the Romanouunit are intercalated with volcanic breccias, banakitic lavas,airfall tuffs, and terrigenous sediments. Ignimbrites and ande-sites from the Romanou unit yielded whole rock K-Ar ages of20.50.9 Ma and 20.20.8, respectively (Fytikas et al. 1980;Innocenti et al. 1994; Pe-Piper and Piper 2002). The upper-most volcanic unit, the Myrina unit, overlies the Romanouunit and is composed of K-rich dacite, with lesser amounts ofandesite and trachyte, which are associated with hydrothermalbreccias lithologically similar to those in the Katalakon unit,lava flows, and lahars. Dacites and andesites of the Myrinaunit yielded groundmass, sanidine, and biotite K-Ar agesranging from 19.30.3 to 17.90.4 Ma (Fytikas et al. 1980;Innocenti et al. 1994; Pe-Piper and Piper 2002). Both thevolcanic rocks and the sedimentary basement of LimnosIsland are intermittently overlain by a Pliocene to recentalluvial sedimentary unit that is composed of conglomerates,calc-arenites, and sandstones.

Faults and joints occur in both the igneous and sedimen-tary rocks, and gentle to open folds occur in the sedimentarybasement rocks (Roussos et al. 1993; Innocenti et al. 1994;Tranos 2009). The axes of these folds trend E-W and WSW-ENE and gently plunge (~11) to the WSW (Tranos 2009).Folding does not affect the Miocene volcanic rocks.

Faults are pervasive throughout the island (up to 7 km long)and occur in three dominant orientations, NE-SW, ENE-WSW,and E-W. Minor populations of faults are oriented NNESSW(N10E to N30E) and NWSE to NNWSSE (Tranos 2009).These different orientations led Tranos (2009) to conclude thatfive discrete regional-scale deformational events were

responsible for the faulting. Faults and associated deformation-al features crosscut both the sedimentary basement and theoverlying volcanic rocks.

Geology of the Fakos area

The Fakos prospect occurs in an area topographically de-fined by two large hills, the western Tourlida Hill and theeastern Petrospitos Hill, both of which are ~300 m in eleva-tion. Their prominence is controlled by subvolcanic intru-sions that were emplaced into the sedimentary host rocks(Fig. 3). The sedimentary basement on Fakos Peninsula iscomposed largely of medium-grained quartz-rich sandstonesand claystones that were silicified by hydrothermal fluids(Fig. 4a). Finely disseminated sulfides are pervasive in thesesandstones.

The sedimentary basement rocks were intruded and over-lain by the oldest plutonic rocks and volcanic rocks foundon Limnos Island, which are comprised of andesitic lavaflows, tuffs, and trachyandestic subvolcanic intrusions of thesouthern-most exposures of the Katalakon unit (Fig. 3). Atthe north end of Fakos Peninsula, there is a small outcrop ofpyroclastic rock of the Romanou unit (Roussos et al. 1993;Innocenti et al. 1994; Pe-Piper and Piper 2002; Voudouris2006; Pe-Piper et al. 2009). Based on the classificationscheme of Le Bas et al. (1986), the extrusive rocks onFakos Peninsula range from shoshonitic andesites (latites),to trachyandesites, and trachytes (Innocenti et al. 1994;Voudouris 2006; Pe-Piper et al. 2009).

Towards the central part of Fakos Peninsula, the extrusiveand sedimentary basement rocks were intruded by a subvol-canic microporphyrytic quartz monzonite (the Fakos quartzmonzonite) (Voudouris and Alfieris 2005; Voudouris 2006;Pe-Piper et al. 2009) (Fig. 3). Pe-Piper et al. (2009) suggestedthat the Fakos quartz monzonite is genetically related to theemplacement of other subvolcanic intrusions of the Katalakonunit due to its age, chemistry, and proximity to the Katalakonunit instrusives. Late-stage, E-W trending, alkaline dikeswarms crosscut the Fakos quartz monzonite and the adjacentrocks (Roussos et al. 1993; Voudouris and Skarpelis 1998; Pe-Piper and Piper 2002; Voudouris 2006; Kamvisis 2010)(Fig. 4b).

Much of the southwestern portion of Limnos Island wassubjected to hydrothermal alteration along fault zones(Papoulis and Tsolis-Katagas 2008). Four discrete zones ofhydrothermal alteration have been identified based on claymineralogy: smectite, illite, halloysite, and kaolinite-dickitezones. However, the smectite and illite zones are uncommon(Papoulis and Tsolis-Katagas 2008).

The Fakos Peninsula, like the rest of Limnos Island, iscrosscut by many major NE-SW and ENE-WSW-trendingfaults. These structures controlled the emplacement of thesubvolcanic bodies and facilitated the flow of magmatic-

Fakos transitional porphyry Cu to epithermal Au-Te mineralization 89

hydrothermal fluids that were responsible for the metallicmineralization (Voudouris 2006; Tranos 2009). The Fakosquartz monzonite and adjacent host rocks were locally sub-jected to intense hydrothermal alteration (Voudouris andAlfieris 2005; Voudouris 2006; Papoulis and Tsolis-Katagas2008). Recent subsidence of Fakos Peninsula is inferred tohave occurred as a result of extension along en echelon normalfaults.

Samples and analytical methods

Major oxide and trace element (including REE) composi-tions of 31 samples of igneous and sedimentary rock relatedto the metallic mineralization were obtained from ACMEAnalytical Laboratory, Vancouver, Canada, (Acme methods4A and 4B) using inductively coupled plasma (ICP)-emis-sion spectrometry (ES) and ICP-mass spectrometry (MS),respectively, after the samples were subjected to lithiummetaborate-tetraborate fusion and dilute nitric acid digestion.Loss on ignition was obtained by measuring the mass differ-ence of each sample prior to and subsequent to roasting at1000C. Total carbon and sulfur were measured be Lecoanalysis. Base metal (Cu, Pb, and Zn) and precious metalcontents were ascertained by dissolution of samples in aqua

regia followed by ICP-MS analysis. Standards used byACME Analytical are accurate to within 2 percent for majorelements and 5 ppm for trace elements. The whole rockgeochemical results of selected samples are given in Table 1.

Sixty surface samples were collected of igneous andsedimentary rocks that host metal-bearing quartz veins forpetrographic, fluid inclusion, stable isotope, and electronmicroprobe studies. Thin and polished thin sections of hostrocks and metal-bearing veins were studied with a polariz-ing microscope at Iowa State University, and a JEOL JSM5600 scanning electron microprobe equipped with back-

Alunitic

Silicic

Sericitic / Argillic

Potassic / Propylitic

TourlidaHill

PetrospitasHill

TourlidaHill

PetrospitasHill

Katalakon Unit: Fakos quartz monzonite

Paleogene SedimentaryBasement

Katalakon Unit: Subvolcanic intrusions

Faults

N

0.50 km

Primitive Roads

B

3949' N

22 10' E

A

Fig. 3 a Geological map of the study area on Fakos Peninsula showing trends of local faults and, b Approximate extent of the hydrothermalalteration zones superimposed onto the local geology

Fig. 4 a Silicified sandstones that form the basement on Fakos Pen-insula. In places, the bedding is obliterated by intense hydrothermalalteration. b Dark-colored alkalic dike that crosscuts the Fakos quartzmonzonite. c and d Quartz stockworks surrounded by potassicallyaltered host rock associated with porphyry-style mineralization. eFakos quartz monzonite pervasively altered by K-feldspar and magne-tite. f Large-scale quartz vein system trending roughly EW that isspatially associated with epithermal-style polymetallic mineralization.g and h Quartz-tourmaline veins associated with sericitic alteration. iSericitically altered monzonite breccia cemented by tourmaline. jQuartz-calcite-telluride veinlet associated with Stage 3 epithermalmineralization. k Potassically altered Fakos quartz monzonite. l Alu-nitic alteration with native sulfur. m Quartz vein system developedacross Fakos Peninsula with alunitic-silicic lithocap visible in thebackground. n Vuggy-silica alteration showing silica deposition intohollows

b

90 A.P. Fornadel et al.

Fakos transitional porphyry Cu to epithermal Au-Te mineralization 91

Table1

Whole-rockchem

istry

Sam

ple

AF-4

AF-21A

AF-75

AF-76

AF-84

AF-99

AF-101

PP-LM45*

PP-LM48*

PP-LM50*

AF-8

AF-21b

AF-5

AF-14

AF-15

AF-16

AF-17

AF-25

AF-27

AF-34

AF-47

AF-64A

AF-64B

Lithology

qmz

qmz

qmz

qmz

qmz

qmz

qmz

qmz

qmz

qmz

dike

dike

dkqm

zss

ssss

ssss

ssss

ssss

ss

SiO

2(wt.%)

60.58

58.71

69.73

62.31

66.92

65.57

61.83

59.7

60.2

58.4

57.51

59.25

59.48

82.85

88.06

76.42

72.21

84.87

89.24

78.17

74.96

81.82

74.53

TiO

20.74

0.75

0.4

0.7

0.52

0.46

0.64

0.78

0.79

0.84

0.82

0.64

0.56

0.33

0.27

0.27

0.74

0.33