Tennantite-tetrahedrite series from the Madan Pb-Zn deposits, Central Rhodopes, Bulgaria

ORIGINAL PAPER

Tennantite-tetrahedrite series from theMadan Pb-Zn deposits,Central Rhodopes, Bulgaria

Rossitsa D. Vassileva & Radostina Atanassova &

Kalin Kouzmanov

Received: 31 January 2013 /Accepted: 30 October 2013# Springer-Verlag Wien 2013

Abstract Minerals from the tennantite-tetrahedrite series(fahlores) are found as single euhedral crystals and crustiformaggregates in hydrothermal veins of the Gradishte and PetrovitsaPb-Zn deposits of the Madan ore field, southern Bulgaria.Unusually large compositional variations and fine oscillatorycrystal zoning were investigated with electron microprobe anal-ysis. TheGradishte samples correspond dominantly to tennantite,while Petrovitsa crystals have exclusively tetrahedrite composi-tion. Fahlore compositions at Madan correspond to zincian vari-eties (1.6–1.95 apfu), with low Fe-content (<0.45 apfu). Minorsilver is characteristic only for the Petrovitsa samples, reaching amaximum of 0.30 apfu. The (Cu+Ag) content of the Petrovitsatennantites and the Cu content of the Gradishte tetrahedritessystematically exceed 10 apfu resulting in compensation of theexcess Cu in the structure by Fe3+. Textural characteristics,mineral relationships and available fluid inclusion and stableisotope data suggest that fahlores precipitated in the late stagesof mineralization at Madan, at temperature interval of 300–200 °C from oxidizing fluids with mixed (magmatic-meteoric)signatures.

Introduction

The polymetallic hydrothermal deposits in Central Rhodopesare the largest accumulation of economically important Pb-Zn

ores in southern Bulgaria (Laki, Davidkovo, Ardino,Enyovche, and Madan ore fields, from north to south;Kolkovski and Dobrev 2000; Fig. 1a) and northern Greece(Thermes; Kalogeropoulos et al. 1996). During the last50 years the deposits in the Madan area alone produced morethan 100 million tons of Pb-Zn ores with an average grade of2.5 % Pb and 2.1 % Zn (Milev et al. 1996; Vassileva et al.2009a). Together with Thermes, the Central Rhodopean dis-trict produced a total amount of about 6 Mt of Pb+Zn, whichdefines the region as an important Pb-Zn ore province(Andrew 2003) and one of the most significant manifestationsof vein-type Pb-Zn mineralization in the world (Kolkovskiand Dobrev 2000).

The tennantite-tetrahedrite solid solution series, alsoknown as the fahlore group, is among the most commonsulfosalts occurring in different amounts in many sulfidedeposits worldwide. Tetrahedrite-tenanntitess occur extensive-ly in many base-metal deposits although they have subordi-nate role compared to major sulfides. They are the mostcommon economic ore minerals of silver and often containat least trace amounts of Hg, Bi, Te, Zn, Cd, Sn, Pb, and Se(Mozgova and Tsepin 1983). Compositional variations of themost common sulfosalt solid solution, i.e. tennantite-tetrahedrite, have been extensively studied by many authors(e.g. Charlat and Levy 1974, 1975; Mozgova and Tsepin1983; Sack and Loucks 1985; Spiridonov et al. 2005;Kharbish et al. 2007a). Based on a study of the compositionaltrends in natural and synthetic tetrahedrites and consideringthe most common minor elements in the fahlore structure,Johnson et al. (1986) suggested the generalized formula (Cu,Ag)6Cu4(Fe, Zn, Cu, Hg, Cd)2(Sb, As, Bi, Te)4(S, Se)13.Although Cu is always the predominant metal, considerablesubstitution takes place by Fe and Zn, and less commonly alsoby Ag and Hg. Ratios between different metals and semi-metals were successfully used to study compositional zoningof fahlores on an ore body, deposit to a district scale, reflecting

Editorial handling: A. Beran

R. D. Vassileva (*) : R. AtanassovaGeological Institute, Bulgarian Academy of Sciences, Acad. G.Bonchev Str. 24, 1113 Sofia, Bulgariae-mail: [email protected]

K. KouzmanovDepartment of Earth Sciences, University of Geneva, Rue desMaraîchers 13, CH-1205 Geneva, Switzerland

Miner PetrolDOI 10.1007/s00710-013-0316-0

the evolution of intensive parameters of ore-forming fluids(e.g.temperature, redox state) and fluid-rock interaction (e.g.Wu and Petersen 1977; Marcoux et al. 1994; Kouzmanovet al. 2004; Catchpole et al. 2012).

Despite the work that has been done on defining mineralassociations and chemical composition of the fahlores in thePb-Zn deposits of the Madan (Mincheva-Stefanova 1960;Bonev 1973; Malinov 1987; Kolkovski et al. 1996;Vassileva and Atanassova 2009), Davidkovo (Marinova andKolkovski 1994), and Laki (Kolkovski et al. 2001; Vangelovaand Kolkovski 2007) ore fields, the chemical variations andzoning of the tetrahedrite-tennantite from the CentralRhodopean polymetallic district were not systematically stud-ied till now. Although the members of the series were consid-ered as important ore minerals of Cu and Ag at Davidkovo

(Marinova and Kolkovski 1994) and Laki (Kolkovski et al.2001; Vangelova and Kolkovski 2007), in the Madan depositsthey are subordinate to rare compared to the main base-metalsulfides sphalerite, galena, and chalcopyrite. At Madan, thefahlore group always reveals increased Zn-contents, first re-ported in tetrahedrite from the Gradishte and Borieva deposits(Kirov and Mincheva-Stefanova 1962; Mincheva-Stefanovaet al. 1964).

In the present contribution we systematically investigatethe mineral association, crystal morphology, compositionalzoning, and textural relationships of mm-sized well shapedcrystals and aggregates of fahlores from the Gradishte andPetrovitsa deposits in the Madan ore field. We report a largedataset of electron microprobe analyses of the minerals anddiscuss the observed compositional variations as indicators of

Fig. 1 a Simplified geological map of the Central Rhodopean base-metalore district with Madan, Ardino, Davidkovo, and Laki ore fields (fromsouth to north). Thermes ore field in northern Greece is not indicated onthe map; b Geological map of theMadan ore field; location of the studied

Petrovitsa and Gradishte deposits (in yellow) and the mentioned in thetext Strashimir, Pechinsko, Spoluka, andGoliam Palas deposits (in white)is shown; modified after Ivanov et al. (2000)

R.D. Vassileva et al.

the physico-chemical parameters of ore formation in theMadan deposits, compared to other Tertiary Pb-Zn depositsfrom southern Bulgaria.

Geological setting

The Tertiary (~30 Ma) hydrothermal Pb-Zn deposits of theCentral Rhodopes, in southern Bulgaria and northern Greece,are hosted by a metamorphic core complex in a dome-likestructure (Kolkovski et al. 1996; Kalogeropoulos et al. 1996;Ivanov et al. 2000; Kolkovski and Dobrev 2000; Kaiser-Rohrmeier et al. 2004, 2013; Marchev et al. 2005; Fig. 1a).In the largest Madan ore field, the southernmost on theBulgarian territory, the mineralization is controlled by sixlarge, up to 10–15 km long, NNW-trending subvertical majorfault zones (Kolkovski et al. 1996; Fig. 1b). The mineraliza-tion is mainly hosted by the Madan allochthon unit, consistingof alternations of gneisses, schists, amphibolites and marbles(Fig. 1b). Two levels of marbles in the lower part of theMadanunit, known as “2nd and 3rd marble horizons” are the mainhost for large replacement ore bodies, see below. Rhyolitedikes with WNW-ESE direction occur in the northern part ofthe ore field and pre-date the polymetallic mineralization(Kolkovski et al. 1996; Marchev et al. 2005; Kaiser-Rohrmeier et al. 2013).

The Madan Pb-Zn deposits are characterized by threemorphogenetic types of ore bodies: veins, stockworks,and replacement metasomatic ore bodies (Vassilevaet al. 2009a). The subvertical veins and complexstockwork zones follow the NNW-striking structures,cross-cutting various gneisses, amphibolites and marblesof the host metamorphic complex. The veins representregularly-shaped, simple, steeply-dipping mineralizedsections of the ore-bearing faults. Apophyses are com-mon, generally joining the main vein at depth. Irregularin shape complex stockwork bodies consisting of sulfideveinlets and impregnations are common in the deepestlevels of the deposits and formed in zones with inten-sive hydrothermal alteration. Complex replacementmetasomatic (skarn) ore bodies are developed at theintersections of the ore-controlling faults with the mar-ble horizons. The morphology of the replacement bodiesis additionally complicated by post-mineralizationstructures.

Bonev and Piperov (1977) considered boiling ofhigh-temperature (up to 350 °C) and low-salinity (generally<5 wt.% NaCl equiv) hydrothermal fluids as a major factor ofore-formation in the Madan district and proposed the firstmodel for base-metal deposition in the Central Rhodopeandistrict. Recently, Kostova et al. (2004) and Kotseva et al.(2011) reported the first fluid inclusion LA-ICP-MS analysesfrom the Madan deposits, providing direct data on the metal

concentrations of ore-forming fluids: Pb–10s ppm, Zn–10s to100 s ppm, Mn–100 s ppm, As and Sb–several 100 s ppm.

Paragenesis of the hydrothermal base-metalmineralization

Based on mineral relationships, three main mineralizationstages have been established in the Madan Pb-Zn deposits(Bogdanov 1961; Kirov and Mincheva-Stefanova 1962;Mincheva-Stefanova and Gorova 1965; Bonev 1982;Vassileva and Bonev 2001, 2003; Fig. 2). Fluid inclusionmicrothermometry measurements in transparent minerals in-dicated temperatures of ore formation ranging from 350°down to ~200 °C (Krasteva 1977; Strashimorov et al. 1985;Bonev and Kouzmanov 2002; Kostova et al. 2004; Vassilevaet al. 2009b).

1. Pre-ore stage. The earliest stage in the area correspondsto skarn formation at the expense of marble horizons in theRhodopean metamorphic complex. The exoskarns are of in-filtration type, distal, without direct link to magmatism.Temporally, these skarns are clearly pre-ore, without anyprimary sulfide formation. Primary mineral association ofthe skarn bodies consists of manganoan silicates dominatedby hedenbergite-johannsenite radial pyroxene aggregates, lat-er overprinted by Mn-pyroxenoids (rhodonite and bustamite),Mn-amphiboles, manganilvaite, chlorites, carbonates, andquartz (Vassileva and Bonev 2001, 2002; Bonev et al. 2005;Zotov et al. 2005). Retrograde hydrothermal alteration afterskarns results in the formation of a favorable environment forsulfide deposition (Vassileva and Bonev 2003).

The skarns exhibit well developed lateral and verticalzoning def ined by changing Mn/Fe ra t ios inclinopyroxenes (Vassileva 2004). Compared to other skarntypes (Meinert et al. 2005), manganoan skarns are formedat relatively lower temperatures. Microthermometry ofpyroxene-hosted fluid inclusions revealed temperature ofhomogenization (Th) of 420–400 °C (Vassileva et al.2009b). Simultaneously with the skarn formation, quartz-sericite ± chlorite and epidote-chlorite alteration assem-blages formed in the silicate wallrocks (gneisses, amphib-olites), along the ore-controlling faults, thus reflecting themildly acidic character of the fluids (Tzvetanov 1975;Kolkovski et al. 1980).

2. Base-metal (main ore) stage consists of three substagesdefined as follows: quartz-pyrite, quartz-galena, and quartz-galena-sphalerite. Galena prevails over sphalerite in the veins(typically Pb:Zn=1.5–2.5), while sphalerite is more abundantin the skarn-hosted replacement ore bodies (Pb:Zn=0.5–1).Chalcopyrite is the main copper mineral. Subordinate to rareminerals include arsenopyrite, tennantite-tetrahedrite, pyrrho-tite, and various Ag- and Bi-sulfosalts. The temperature of oreformation, according to fluid inclusion microthermometry

Tennantite-tetrahedrite series from the Madan Pb-Zn deposits

data, is relatively high: 350–250 °C (Strashimorov et al. 1985;Kolkovski et al. 1996; Kostova et al. 2004; Vassileva et al.2009b; Kotseva et al. 2011).

3. Carbonate (post-ore) stage. The stage includes the depo-sition of late gangue mineralization represented by carbonates,quartz, chalcedony, and barite, associated with rare sulfides, andAg-and Bi-sulfosalts (Kolkovski et al. 1996). The temperature offormation of this assemblage, obtained by fluid inclusionmicrothermometry on gangue minerals ranges from 260° to200–180 °C (Strashimorov et al. 1985; Vassileva et al. 2009b).In a study of fluid inclusions in sphalerite from the carbonatestage in several Madan deposits Bonev and Kouzmanov (2002)reported Th of 220–200 °C for primary fluid inclusions and of185–160 °C for secondary ones.

Samples and analytical techniques

Representative tennantite-tetrahedrite samples from the deepmining levels of the Gradishte (level 400) and the upper levelsof the Petrovitsa (level 970) deposits were used in this study.The samples from both deposits originate from the vein orebodies. Tennantite-tetrahedrite minerals were not found in themetasomatic bodies.

Mineral relationships were systematically studied byreflected-light microscopy prior to electron microscopy usingbackscattered electron (BSE) imaging. A secondary electronimaging (SEI) on carbon-and gold-coated samples was used todetermine the morphological characteristics of the crystals.

Electron microprobe analyses (EMPA) and elemental X-ray mapping were carried out using the Jeol JXA 8200

Superprobe WD/ED combined microanalyzer at theUniversity of Lausanne. Operating conditions were accelerat-ing voltage of 20 kV, beam current of 20 nA, and beamdiameter of 1 μm. Standards and radiations used were asfollows: FeS2 (Fe-Kα, S-Kα), GaAs (As-Lα), Sb2S3 (Sb-Lα), Cu5FeS4 (Cu-Kα), Bi2Se3 (Bi-Mα), CdSe (Cd-Lα, Se-Lα), MnS (Mn-Kα), ZnS (Zn-Kα), SnS (Sn-Lα), HgS (Hg-Mα), Te metal (Te-Lα), Ag metal (Ag-Lα). Counting timesof 20 s on peak and 10 s on background on both sides of thepeak were used for all elements. Limits of detection (LOD)were calculated as the minimum concentration requiredto produce count rates three times higher than the squareroot of the background (3σ; 99 % degree of confidenceon the lowest detection limit). LODs and averaged ana-lytical errors are reported together with data results inTables 1 and 2. Concentrations below LOD are reportedas not detected. Overlap and matrix corrections werecarried out following the established protocol and soft-ware in the laboratory.

Laser-ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS) analyses were performed at theGeological Institute of BAS, Sofia, using a 193 nm ArFexcimer laser coupled with an ELAN DRC-e ICP quadrupolemass spectrometer (Peytcheva et al. 2009). For controlledablation, an energy density higher than 10 J/cm2 on the sampleand a laser pulse frequency of 10 Hz were used. Analyseswere performed with a beam diameter of 75 μm. Externalstandardization on NIST glass standard SRM-610 providedrelative element concentrations, which were transformed intotrue values by internal standardization (using Cu concentra-tion determined by EMPA).

Fig. 2 Generalized mineralparagenetic sequence in theMadan base-metal deposits.Thick bars indicate higherabundances, thin and dashed linesrefer to lower abundances; arrowsmark mineral transformationscommon for the replacementmetasomatic ore bodies


Tab

le1

Representativeelectron

microprobeanalyses

oftennantite-tetrahedritefrom

theGradishtedeposit

Sample

Gr2-2A

Gr2-2A

1profile

Gr2-2B

LOD

Error

Analysis#

34

56

78

910

1112

1314

1516

1718

1920

2122

23

Cu(w

t%)

42.85

40.85

39.75

41.07

43.04

39.28

39.50

39.76

39.76

43.44

42.40

41.25

40.09

40.25

40.56

42.80

43.89

41.04

42.76

41.48

43.31

0.10

0.29

Zn

7.63

7.81

7.66

7.53

7.26

7.43

7.56

7.69

7.69

7.35

7.64

7.89

7.79

7.68

7.86

7.84

7.93

8.03

7.79

7.73

7.73

0.11

0.13

Fe0.96

0.39

0.36

0.58

1.05

0.53

0.31

0.29

0.29

1.07

0.87

0.67

0.94

0.86

0.40

0.52

0.58

0.29

0.50

0.48

0.72

0.07

0.05

Snn.d.

n.d.

0.10

n.d.

n.d.

0.11

0.14

0.12

0.12

n.d.

0.07

n.d.

0.08

0.11

0.12

n.d.

n.d.

0.09

n.d.

0.08

n.d.

0.06

0.03

Sb2.03

12.73

18.80

11.50

2.42

16.65

21.20

19.76

19.76

0.33

4.60

12.09

17.71

17.09

18.03

6.26

0.64

13.82

2.28

11.12

0.27

0.15

0.21

As

19.05

11.02

6.94

11.84

18.62

8.39

5.14

6.13

6.13

20.30

16.97

11.67

7.92

8.20

7.52

15.77

20.08

10.38

18.73

12.50

20.10

0.25

0.22

S27.52

26.25

25.48

26.30

27.37

25.66

25.16

25.65

25.65

27.71

27.35

26.28

25.70

25.51

25.50

27.27

27.90

26.10

27.53

26.34

27.90

0.09

0.28

Total

100.04

99.04

99.08

98.82

99.76

98.04

99.01

99.39

99.39

100.20

99.91

99.85

100.23

99.71

99.98

100.45

100.99

99.75

99.59

99.73

100.02

Cu(apfu)

10.09

10.14

10.13

10.16

10.18

10.08

10.18

10.12

10.14

10.15

10.09

10.14

10.05

10.13

10.23

10.20

10.19

10.18

10.12

10.18

10.12

Zn

1.74

1.88

1.90

1.81

1.67

1.84

1.89

1.90

1.93

1.67

1.77

1.88

1.90

1.88

1.93

1.82

1.79

1.94

1.79

1.84

1.75

Fe0.26

0.11

0.10

0.16

0.28

0.15

0.09

0.08

0.12

0.28

0.24

0.19

0.27

0.25

0.11

0.14

0.15

0.08

0.14

0.13

0.19

Sn0.01

0.01

0.02

0.02

0.02

0.01

0.01

0.02

0.02

0.01

0.01

Sb0.25

1.65

2.50

1.48

0.30

2.21

2.85

2.62

2.53

0.04

0.57

1.55

2.32

2.25

2.37

0.78

0.08

1.79

0.28

1.42

0.03

As

3.81

2.32

1.50

2.48

3.74

1.81

1.12

1.32

1.36

4.02

3.43

2.43

1.69

1.75

1.61

3.19

3.95

2.18

3.76

2.60

3.98

S12.85

12.90

12.86

12.90

12.83

12.96

12.85

12.94

12.90

12.83

12.90

12.80

12.77

12.73

12.74

12.88

12.84

12.82

12.91

12.81

12.92

Σcat

16.15

16.10

16.14

16.10

16.17

16.04

16.15

16.06

16.10

16.17

16.10

16.20

16.23

16.27

16.26

16.12

16.16

16.18

16.09

16.19

16.08

As/(A

s+Sb

)0.94

0.58

0.37

0.63

0.93

0.45

0.28

0.34

0.35

0.99

0.86

0.61

0.42

0.44

0.40

0.80

0.98

0.55

0.93

0.65

0.99

Fe/(Fe+Zn)

0.13

0.06

0.05

0.08

0.15

0.08

0.05

0.04

0.06

0.15

0.12

0.09

0.12

0.12

0.06

0.07

0.08

0.04

0.07

0.07

0.10

Structuralformulae

calculated

inatom

sperform

ulaunit(apfu)

basedon

Σatom

s=29

LOD—lim

itof

detectionin

wt%

;Error—averagevalueforthelower

andhigher

countrates

forsinglemeasurement,averaged

forthesetm

easurements,inwt%

Mn,Ag,Se,T

e,HgandBiare

system

atically

belowtheelectron

microprobedetectionlim

it:0.03,0.20,0.21,0.05,0.10,and

0.13

wt%

,respectively;

n.d.=notd

etected


Tab

le2

Representativeelectron

microprobeanalyses

oftennantite-tetrahedritefrom

thePetrovitsadeposit

Sample

SP1B

profile

SP1B

LOD

Error

Analysis#

5556

5758

5960

6162

6364

6869

7071

7273

7475

Cu(w

t%)

40.21

39.45

39.29

38.85

38.44

38.36

38.71

37.96

38.81

37.33

38.54

39.21

37.70

37.83

38.33

37.37

37.54

37.51

0.10

0.29

Ag

0.77

0.96

0.98

1.18

1.34

1.38

1.45

1.36

0.98

1.57

1.12

1.11

1.50

1.59

1.56

1.64

1.70

1.80

0.27

0.15

Zn

7.87

7.83

7.81

7.53

7.36

7.27

7.25

7.13

7.52

6.99

7.54

7.36

7.20

7.44

7.30

7.25

7.24

7.47

0.11

0.13

Fe0.27

0.27

0.24

0.38

0.44

0.58

0.60

0.54

0.38

0.50

0.49

0.59

0.50

0.35

0.46

0.44

0.41

0.42

0.07

0.05

Sn0.07

0.08

0.12

0.11

0.12

0.08

0.12

0.15

0.11

0.12

0.11

0.08

0.14

0.12

0.10

0.11

0.12

0.15

0.06

0.03

Sb17.33

18.62

18.33

21.75

23.68

23.84

22.46

25.16

21.12

26.07

22.26

19.54

26.23

26.09

23.72

26.29

26.08

26.31

0.15

0.21

As

7.90

7.14

7.36

4.69

3.74

3.49

4.29

2.31

5.33

1.78

4.60

6.66

1.91

1.76

3.53

1.69

1.73

1.55

0.25

0.22

S25.42

25.44

25.60

25.09

24.71

24.64

24.97

24.73

24.89

24.15

24.99

25.66

24.43

24.52

24.74

24.58

24.25

24.55

0.09

0.28

Total

99.84

99.78

99.72

99.57

99.83

99.64

99.85

99.35

99.14

98.52

99.65

100.20

99.61

99.69

99.73

99.37

99.06

99.77

Cu(apfu)

10.16

10.02

9.97

10.02

10.00

10.01

10.00

9.96

10.04

9.96

9.96

9.94

9.94

9.96

9.99

9.87

9.97

9.88

Ag

0.11

0.14

0.15

0.18

0.21

0.21

0.22

0.21

0.15

0.25

0.17

0.17

0.23

0.25

0.24

0.26

0.27

0.28

Zn

1.93

1.93

1.93

1.89

1.86

1.84

1.82

1.82

1.89

1.81

1.89

1.81

1.84

1.90

1.85

1.86

1.87

1.91

Fe0.08

0.08

0.07

0.11

0.13

0.17

0.18

0.16

0.11

0.15

0.14

0.17

0.15

0.11

0.13

0.13

0.12

0.12

Sn0.01

0.01

0.02

0.01

0.02

0.01

0.02

0.02

0.02

0.02

0.01

0.01

0.02

0.02

0.01

0.02

0.02

0.02

Sb2.29

2.47

2.43

2.93

3.22

3.25

3.03

3.45

2.85

3.63

3.00

2.58

3.61

3.58

3.23

3.62

3.61

3.62

As

1.69

1.54

1.58

1.03

0.83

0.77

0.94

0.52

1.17

0.40

1.01

1.43

0.43

0.39

0.78

0.38

0.39

0.35

S12.73

12.81

12.87

12.83

12.74

12.74

12.79

12.87

12.76

12.77

12.80

12.89

12.77

12.79

12.77

12.86

12.76

12.82

Σcat

16.27

16.19

16.13

16.17

16.26

16.26

16.21

16.13

16.24

16.23

16.20

16.11

16.23

16.21

16.23

16.14

16.24

16.18

Ag/(A

g+Cu)

0.01

0.01

0.01

0.02

0.02

0.02

0.02

0.02

0.01

0.02

0.02

0.02

0.02

0.02

0.02

0.03

0.03

0.03

As/(A

s+Sb

)0.43

0.38

0.39

0.26

0.20

0.19

0.24

0.13

0.29

0.10

0.25

0.36

0.11

0.10

0.19

0.09

0.10

0.09

Fe/(Fe+Zn)

0.04

0.04

0.03

0.06

0.07

0.08

0.09

0.08

0.06

0.08

0.07

0.09

0.08

0.05

0.07

0.07

0.06

0.06

Structuralformulae

calculated

inatom

sperform

ulaunit(apfu)

basedon

Σatom

s=29

LOD—lim

itof

detectionin

wt%

;Error—averagevalueforthelower

andhigher

countrates

forsinglemeasurement,averaged

forthesetm

easurements,inwt%

Mn,Se,Te,H

gandBiare

system

atically

belowtheelectron

microprobedetectionlim

it:0.04,0.21,0.06,0.09,and0.14

wt%

,respectively


Mineral relationships and morphological characteristics

Mineralogy and textures

The mineral associations of the studied samples are shown inFig. 3. The tennantite-tetrahedrites from Gradishte areintergrown with quartz, sphalerite, galena, and chalcopyriteof the base metal stage. The sulfosalts occur predominantly asidiomorphic crystals which postdate chalcopyrite and pyriteaggregates and are overgrown in turn by late carbonates(Fig. 3a). Tennantite-tetrahedrites form irregularly shaped

overgrowths and in the peripheral zones triangular chalcopy-rite inclusions are embedded in a fahlore matrix (Fig. 4a).Chalcopyrite relics give a textural evidence of oriented re-placement of the mineral by fahlores.

Tetrahedrites from Petrovitsa are associated intimately withthe main sulfides but they are formed later than and corrodeslightly sphalerite and galena or penetrate chalcopyrite(Fig. 3b–d). The galena and chalcopyrite crystals are partlyto intensively affected by natural dissolution. However, thisprocess has not left macroscopic marks on the tetrahedritecrystal faces. In polished sections galena occurs as

Fig. 3 Textural relationships oftennantite-tetrahedrite with themain base-metal sulfides fromGradishte (a) and Petrovitsa (b–e) deposits: a Tennantite-tetrahedrite crustiform aggregateintergrown with carbonates andovergrowing large chalcopyritecrystals; b Tetrahedrite associatedwith chalcopyrite and sphaleriteovergrowing large galenacrystals; c Crust of polyhedraltetrahedrite crystals overgrowingpartly dissolved galena andchalcopyrite; d Tetrahedriteassociated with quartz,overgrowing large sphaleritecrystals; e Position of thetetrahedrite within the mineralsequence in the veinmineralization of the Petrovitsadeposit—single crystals formed atthe boundary between sphalerite-2 and 3, associated withchalcopyrite and galena; see textfor details (composite transmittedlight microphotograph of adoubly polished 150 μm-thicksection). Abbreviations: Cal—calcite,Ccp—chalcopyrite,Gn—galena, Py—pyrite, Qz—quartz,Sp—sphalerite, Tnt—tennantite,Ttr—tetrahedrite; according toWhitney and Evans (2010)


characteristic dissolution forms in association with chalcopy-rite and sphalerite intergrown with tetrahedrite (Fig. 4e). Theproportion between the three minerals changes significantly indifferent parts of the aggregates, suggesting complex inter-growth mechanisms of formation and metasomaticreplacement.

Based on color in transmitted light (Fig. 3e) and Fe-content, as well as intergrowth textures with the other oreand gangue minerals, three generations of sphalerite can bedefined–sphalerite-1 and sphalerite-2 formed during the earlyand late base-metal stage, respectively, and sphalerite-3(completely transparent in transmitted light, Fig. 3e)–duringthe carbonate stage. The timing of fahlore precipitation in thePetrovitsa sample is well constrained and corresponds to thetransition between sphalerite-2 and sphalerite-3 (late in base-metal to early in the carbonate stage).

Crystal morphology

Although crystals are occasionally reported, the fahlore-groupminerals generally occur in nature as small (<l mm) anhedralgrains intergrown with or as inclusions in sulfide minerals(Kostov and Kostov 1999). In the studied samples, however,fahlores occur as millimeter-sized crystals with typical poly-hedral morphologies (Figs. 3 and 5).

The tetrahedral or rhombododecahedral habit of theGradishte tennantite is developed by (111), (1 1̄1), and (110)(Fig. 5a–c). Tennantite overgrows (112) chalcopyrite faceswith parallel mutual orientation (Fig. 5a), due to the similarbasic structural motifs (Bonev 1973). Characteristic penetra-tion twins on {111} are observed (Fig. 5b).

In hand specimens, tetrahedrite from Petrovitsa occurs ascrustiform aggregates associated with sphalerite, galena, and

Fig. 4 Zonation and intergrowth textures of fahlores from Gradishte (a–b ) and Petrovitsa (c–e ) deposits: a Zoned tennantite aggregateintergrown with euhedral chalcopyrite and quartz; electron microprobeanalyses #3–21 are reported in Table 1; b Tennantite overgrowth onpyrite. Note the similarities in the oscillatory zoning pattern between(a) and (b). The inset corresponds to a reflected light microphotographof the same area; c Cross section of a crust aggregate from the sampleshown on Fig. 3c. Note the complex intergrowth textures of tetrahedritewith galena, chalcopyrite and sphalerite in the center of the crust. Base-

metal sulfides in the center of the aggregate served as nuclei for thetetrahedrite formation. The crust has a symmetrical structure, witnessedby the development of voids parallel to the growth banding on both sidesof the crust–bottom and top; d Detail from (c) with large homogeneousgrowth banding. Position of the LA-ICP-MS analyses is shown; data arereported in Table 3; e Dissolution form of galena in association withchalcopyrite, intergrown with tetrahedrite; reflected light microphoto-graph. a–d Backscattered electron (BSE) images. Abbreviations usedas in Fig. 3


chalcopyrite, intergrown with quartz (Figs. 3b–e and 4c–e).Two common textural features were recognized: i)Tetrahedrite crystals completely overgrow and mimic theshape of the base-metal sulfides (Figs. 3c–d and 5e–f). Suchperimorphoses consist of subparallel crystals, reaching 0.5–4 mm in size. They show tetrahedral habit and are shaped byo{111}, d{110}, and small n{211}; ii) Small (up to 1 mm)tetrahedrite single crystals are observed as overgrowth oncuboctahedral galena (Fig. 5e–f), following the scheme galena(100) [100]//tetrahedrite (001) [110]. According to texturalrelationships the single tetrahedrite crystals have formedshortly after the polyhedral crusts.

Compositional variations and zoning

About 100 electron microprobe analyses were obtained fromminerals of the tennantite-tetrahedritess from the Madan de-posits and representative analyses are reported in Tables 1 and2. Electron-microprobe data reveal the existence of completesolid-solution between the tennantite and tetrahedrite end-members from the Gradishte deposit. Most of the crystals

from Petrovitsa are of tetrahedrite composition, showing fre-quent incorporation of Zn, and Fe and Ag to a minor extent.

The tennantite-tetrahedrite from Gradishte displays finezonation pattern parallel to the crystal faces (Fig. 4a–b and6a). Typical for these samples is a compositional “stratigra-phy” occurring as a common zonal feature in different sam-ples and consisting of compositional fluctuation of alternatingfine zones with various width (several-50 μm)—from atennantite core, evolving towards tetrahedrite composi-tion, and changing again back to tennantite (Figs. 4a–band 6a–b). Core-to-rim profiles reveal fluctuating Cu content,slightly increasing Zn and decreasing Fe content, and inverse-ly zoned As and Sb content (Fig. 6b). Elemental X-ray map-ping (Fig. 7) illustrates better these compositional fluctuationson a crystal scale.

The Petrovitsa samples display a different zoning pattern—from intermediate in composition cores towards progressivelyincreasing Sb content and almost pure tetrahedrite rims(Figs. 4c–d and 6c–d). Copper content along core-to-rimprofiles across the crustiform aggregates correlates negativelywith Sb. Particular feature of the Petrovitsa tetrahedrite is aminor Ag content which correlates positively with antimony.

Fig. 5 Fahlore crystalmorphology (Gradishte: a–c ;Petrovitsa: d–f), secondaryelectron images (SEI): a Euhedraltennantite crystals on striatedalong [201] chalcopyrite crystalface. Both minerals show parallelmutual orientation; b Twinned on{111} tennantite crystalsovergrowing chalcopyrite; cEuhedral tennantite crystalsovergrowth on chalcopyrite andpyrite; d Negative (11̄1) andsmall positive (111) tetrahedronsand (211) of tetrahedrite; eTetrahedral crystals shaped by(111) and (110), overgrowinggalena cuboctahedron along<111> direction; f Tetrahedritecrystals faceted by positivetetrahedron (111),rhombododecahedron (110) and(211). Abbreviations used as inFig. 3


Zinc and iron, similarly to the Gradishte samples, displayinverse zonation (Fig. 6d).

The main features of the chemical composition of theGradishte and Petrovitsa tennantite-tetrahedritess are illustrat-ed in Fig. 8 and can be summarized as follows:

As and Sb The electron microprobe data on Gradishte andPetrovitsa samples reveal that the studiedcompositions cover the complete solid solutionfrom pure tennantite to almost pure tetrahedriteend members (Tables 1–2, Fig. 8a). The

Gradishte fahlores belong mostly to tennantiteand intermediate members of the solid solution,with Sb ranging from 0.04 to 2.53 apfu. ThePetrovitsa fahlores are exclusively oftetrahedrite compositions and contain As up to1.69 apfu in the crystal cores; however, Ascontent generally does not exceed 1 apfu.Zoning pattern revealed by BSE imaging onsamples from both deposits is mainly controlledby As-Sb substitutions (Figs. 4, 6 and 7).

Fig. 6 Compositional profilesacross zoned tennantite-tetrahedrite crystals fromGradishte (a–b) and Petrovitsa(c–d) deposits. Electronmicroprobe data are reported inapfu (atoms per formula unit);analyses #55-72 are reported inTable 2. See text for discussion


Cu and Ag Silver content in the studied samples is low—below detection limit of 0.27 wt.% in theGradishte samples and in the range 0.11 to 0.28apfu in the Petrovitsa samples (Tables 1–2;

Fig. 8b). Thus, copper is the dominantmonovalent element. The (Cu+Ag) issystematically above 10 apfu, and excess Cu(Cu after subtraction of 10 (Cu+Ag) atoms for a

Fig. 7 Elemental X-ray mappingof zoned tennantite crystal fromGradishte (sample Gr 2–3), areacorresponds to the BSE imagefrom Fig. 6a

Fig. 8 Compositions of fahloresfrom the Madan Pb-Zn deposits.Location of different deposits isshown in Fig. 1b: a As vs Sb; b Cuvs Ag; c Zn vs Fe; d Compositionsof Cu-excess tennantite-tetrahedritefrom different localities plotted inthe Cu-Fe-Zn system. Cu* is Cu inexcess after subtraction of 10 (Cu+Ag) atoms for a total of 12 metalatoms. Lower field (Cu*=Fe3+)includes compositions whereexcess Cu is compensated by Fe3+.Upper field includes compositionswhere Cu* is not compensated byFe3+ (Cu*>Fe3+) indicatingpresence of Cu2+ and requiring anabsence of Fe2+. Note that all datafrom theMadan deposits plot in theFe3+ field, see text for discussion.Data sources: Gradishte andPetrovitsa deposits—this study;Goliam Palas (Kolkovski et al.1980); single analyses of fahloresare available from Gradishte(Mincheva-Stefanova et al. 1964),Strashimir, Spoluka, and Pechinsko(Breskovska et al. 1984)


total of 12 metal atoms) is a common feature forfahlores from both deposits (Fig. 8c).

Zn and Fe Our microprobe data reveal increased Zn contentswith relatively constant values in the range 1.67-1.93 apfu.Most of the analytical points contain Znclose to 1.85 apfu. Such important Zn-incorporation defines the studied crystals aszincian varieties of the tennantite-tetrahedritess(Fig. 8d). The Fe content is generally low, rangingfrom 0.08 to 0.45 at Gradishte and from 0.06 to0.21 apfu at Petrovitsa. Both elements negativelycorrelate (Fig. 6b and d, Fig. 8c). No clear corre-lation exists between Zn, Fe and As, Sb.

Manganese, Se, Te, Hg, and Bi weresystematically measured as well, however datashow that these elements are below the electronmicroprobe detection limits of 0.04, 0.21, 0.06,0.09, and 0.14 wt.%, respectively.

Traceelements

Due to the very fine crystal zoning of the studiedfahlores, systematic analyses of trace elements byLA-ICP-MS with large enough beam size to al-low lower limit of detection were not possible.However three analyses in a large growth band ofa tetrahedrite crystal from Petrovitsa reveal traceelement concentrations at a ppm level (Table 3;Fig. 4d). Perfect matching exists between majorand minor elements measured by EMPA and LA-ICP-MS. Smooth ablation profiles for most of theelements are indicative of homogeneous elemen-tal distribution along the analyzed volume; rarelyinhomogeneous distribution occurs due to zona-tion or solid inclusions. Cobalt andNi contents arein the 141–154 and 157–190 ppm ranges, re-spectively. Lead ranges from 10 to 52 ppm; Bi, In,and Ge are <1 ppm. Manganese, Se, Te, Ga, Au,and Tl are constantly below the respective limit ofdetections (Table 3).

Composition of the main base-metal sulfides

The base metal sulfides associated with fahlores from Petrovitsawere analyzed by EMPA. Sphalerite from the central parts of thetetrahedrite aggregates shows higher Cd content—1.02 wt.%,Cu–0.67 wt.%, As–0.58 wt.%, Fe–0.48 wt.%, and Ag–0.26 wt.%, compared to those found at the border betweenintermediate and outer zone–Cd (0.57 wt.%), and Cu(0.62 wt.%), which are however enriched in Co (0.21 wt.%)and Te (0.27 wt.%). Chalcopyrite contains Zn (0.26 wt.%), Co(0.20 wt.%) and Te (0.11 wt.%). Galena observed as corrodedcrystals, overgrown by tetrahedrite (Fig. 4e) contains up to1 wt.% Ag and 1.34 wt.% Bi. No As or Sb were detected asminor or trace elements in the studied sulfides by EMPA.

Discussion

Compositional variations and conditions of formation

Fahlore minerals are described from a variety of epithermaldeposits, most of which are Au-bearing, e.g. in Sardinia, Italy(Fadda et al. 2005); Romania (Ciobanu et al. 2005; Cook et al.2005), Austria (Kharbish et al. 2007a); Russia and Uzbekistan(Plotinskaya et al. 2005, 2013), Argentina (Makovicky et al.2005), Oregon, USA (Foit and Ulbricht 2001), Yukon, USA(Lynch 1989). Minerals of the series are minor but widespreadore minerals also in the stratiform and stratabound massivesulfide deposits (Miller and Craig 1983). Recently Catchpoleet al. (2012) described tennantite-tetrahedrite in zonedCordilleran base metal vein and replacement deposits atMorococha, Peru.

In Bulgaria, fahlores have been studied in several prov-inces: in the Chiprovtsi ore region (Atanassov 1975; Dragov1997; Dimitrova et al. 2007), Eastern Rhodopes (Breskovska1988; Breskovska et al. 1985; Tarkian and Breskovska 1990;Bogdanov 1992; Breskovska and Tarkian 1994; Bogdanovand Fillipov 2001), Srednogorie zone (Bogdanov 1992;

Table 3 LA-ICP-MS analyses of tetrahedrite from the Petrovitsa deposit,sample SP-2A

Element point 1* point 2* point 3*

V51 ppm <0.86 <1.4 <2.7

Cr53 ppm <9.3 <17 <37

Mn55 ppm <0.86 <1.3 <3.1

Fe57 wt% 0.34 0.48 0.40

Ni62 ppm 173 190 157

Co59 ppm 152 141 154

Cu65 wt% 38.51 38.11 38.69

Zn66 wt% 8.50 8.16 8.52

Ga69 ppm <0.77 <0.47 <1.9

Ge72 ppm 2.5 <3.0 <5.8

As75 wt% 3.79 3.91 3.85

Se77 ppm <24 <19 <67

Mo95 ppm 1.2 <0.64 <1.8

Ag107 wt% 1.09 1.10 1.18

In115 ppm 0.10 <0.11 <0.21

Sn118 ppm <1.2 <1.6 <3.8

Sb121 wt% 28.56 28.23 27.27

Te125 ppm <5.7 <6.4 <16

Au197 ppm <0.11 <0.10 <0.35

Tl205 ppm <0.04 <0.05 <0.12

Pb208 ppm 52 10 36

Bi209 ppm 0.38 0.36 <0.30

*Analyses were performed in a homogeneous growth band; location ofanalytical points is shown on Fig. 4d


Tarkian and Breskovska 1995; Kouzmanov 2001;Kouzmanov et al. 2004).

Although most of the fahlores from the Central Rhodopeandeposits reported in the literature (e.g. Mincheva-Stefanova et al.1964; Malinov 1987; Vangelova and Kolkovski 2007), revealelevated Zn-contents, those of the present study represent themost zincian tennantite-tetrahedrites described until now (up to1.94 apfu). According to the available data on the Zn-content infahlores the studied samples are among the most Zn-rich mem-bers of natural tennantite-tetrahedrites (Johnson et al. 1986; Foitand Ulbricht 2001; Kharbish et al. 2007b; Catchpole et al. 2012)and are the most zincian fahlores described from Bulgariandeposits (e.g. Breskovska and Tarkian 1994; Dragov 1997;Dimitrova et al. 2007). This chemical feature is related to thegeochemical specialization of the Madan Pb-Zn deposits.

According to the recommendations of the IMACommission on New Minerals, Nomenclature andClassification and to Nickel (1992), the studied minerals fromPetrovitsa and Gradishte deposits could be classified aszincian members of the tennantite-tetrahedrite solid solutionseries based on chemical characteristics and X-ray data. Thelattice parameter a0=10.33(8) Å of zincian tetrahedrite fromPetrovitsa is in agreement with calculated cell parameters fornatural tetrahedrites based on the composition, applying theequation proposed by Johnson et al. (1987). The same authorsstate that the Zn/Fe ratio does not influence the variation in thelattice parameter.

Apart from the high Zn-contents, the examined sulfosaltsare characterized chemically by the large As-Sb substitution.In Petrovitsa As substitutes for Sb only in small proportionswhile in Gradishte this substitution results in an almost com-plete series from the As end-member (0.02 apfu Sb) to arsenictetrahedrite (2.91 apfu Sb). Such a chemical inhomogeneityresulting in fine oscillatory zoning (Figs. 4 and 6) can beexplained by the small-scale fluctuations of As and Sb in themineralizing fluid, due to growth rate kinetics of thetetrahedrite crystals, controlled by the concentrations of theseelements in the reaction zone (Plotinskaya et al. 2005).

Even if our data suggest that at depth (Gradishte–400 m.a.s.l.) tennantite compositions prevail, while at shallowlevels (Petrovitsa–970 m.a.s.l) tetrahedrite is dominant, it isdifficult to generalize this statement for the whole ore field. Inthe Goliam Palas deposit, in the northwestern part of theMadan ore field (Fig. 1b), Kolkovski et al. (1980) reportedfahlore compositions that cover the full range of the solidsolution series (Fig. 8a).

Silver incorporation is often related to the late stage offormation of tetrahedrite, compared to the main sulfide para-genesis as seen in Petrovitsa samples. The latter is in accor-dance with the evidence of Sack and Loucks (1985) thatpositive Sb-Ag correlation is controlled by crystallochemicalfactors enabling Sb-rich tetrahedrite to accommodate more Agthan Sb-poor tetrahedrite.

The studied samples reveal low Fe-contents and variableamounts of Ag, which is in accordance with the compositionof the other sulfides. The associated sphalerite in Petrovitsashows only trace amounts of Fe (up to 0.48 wt.%). Galena ischaracterized by 1 wt.% Ag. The small amounts of Co, Ni, Pbdetermined in the studied fahlore samples are found also in themain ore sulfides at 10s to 100 s ppm level (Vassileva et al.2010).

The geochemical manganoan specialization of the CentralRhodopean district is revealed in the increasedMn-contents ofsilicates (johannsenite-hedenbergite clinopyroxenes,manganoan pyroxenoids, manganilvaite), carbonates andsome ore minerals (Vassileva 2004; Vassileva and Bonev2003; Bonev et al. 2005; Vassileva et al. 2010), metamorphicrocks (Cherneva, personal communication), and even in com-ponents of the surface environment (water and soils;Kerestedjian et al. 2000). In the metasomatic replacementore bodies, the preceding skarn mineralization shows highMn-content and the resulting metasomatic ores, e.g. sphaleriteand chalcopyrite, reveal enhanced Mn-contents (Radulova1996; Kolkovski et al. 1996; Vassileva et al. 2010).Although Mn-rich tetrahedrites are reported by Basu et al.(1984), Burkhart-Baumann (1984), and Damian and Damian(2003), the absence of Mn in the studied minerals (<3 ppm,see Table 3) may be due to the fact that the fahlores atGradishte and Petrovitsa occur only in the vein-type orebodies and thus do not inherit the manganoan signature ofthe metasomatic ore bodies, formed after altered manganoanskarns.

Compared to other deposits from the Madan ore field(Goliam Palas, Strashimir, Pechinsko, and Spoluka), fahloresfrom Petrovitsa and Gradishte have very homogeneous metalcontents (Fig. 8). Among the Madan Pb-Zn deposits, fahloresfrom Goliam Palas have the largest variations in As-Sb, Cu-Ag, and Zn-Fe substitutions (Fig. 8a–c).

Mössbauer spectroscopy studies of 57Fe in synthetictetrahedrite showed that Fe strongly varies from the ferric tothe ferrous state, corresponding to changing Cu content of themineral (Makovicky et al. 1990). The content of Cu and Fe intennantite-tetrahedrite has important implications for the oxi-dation state of Fe and improves the understanding of theformation conditions (Kouzmanov et al. 2004; Catchpoleet al. 2012). If Cu is present in excess of 10 apfu (Cu+Ag),it substitutes for Fe in the ideal Cu+10Fe

2+2(As,Sb)4S13 for-

mula. Tennantite-tetrahedrite with more than 10 apfu (Cu+Ag) was first described by Charlat and Levy (1974) and called“Cu-excess” tennantite after Marcoux et al. (1994). If there issufficient Fe, present as Fe2+, excess Cu+ will be compensatedby Fe3+ until a maximum of 1 apfu Fe is reached. At that point,all Fe is ferric, and the composition can be written asCu+11Fe

3+(As,Sb)4S13. Any further excess Cu will be presentin its divalent state. Additional Zn2+ or Mn2+ will substitutefor Fe2+ (Catchpole et al. 2012). Most of the data from the


Madan deposits reveal Cu excess in the structure of thefahlores. Excess-Cu, if present, is compensated dominantlyby Fe3+ (Fig. 8d), suggesting high oxygen fugacity during theformation of the fahlore-bearing assemblages. According toSpiridonov et al. (2005) important Zn-incorporation in thefahlores is also indicative for high fO2, due to the resultingenhanced Cu2+/Me2+ ratios. Another argument pointing to-wards high oxygen fugacity during the late stages of mineral-ization in the Madan deposits is the common presence ofhematite and epidote towards the end of the base-metal stageand at the beginning of the carbonate stage (Fig. 2).

The precipitation of tennantite-tetrahedrite minerals onlyduring the late stages of ore formation in Madan indicatesincreased As and Sb activity in the fluids. This is in goodagreement with recently reported increased As and Sb concen-trations in late-stage ore-forming fluids from the Laki ore fieldin the northern part of the Central Rhodopean district (Buret2012). Arsenic and Sb, being very soluble at low temperaturesand transported as stable neutral hydroxyl complexes Sb(OH)3and As(OH)3 in hydrothermal environment over a wide rangeof temperatures (Zotov et al. 1995, 2003), can be easily fixed assulfosalt minerals when the base metals are not anymore avail-able in high concentrations, due to precipitation, but there is stillavailable reduced sulphur in the fluid.

When compared to other Tertiary Pb-Zn deposits from orefields from the central and northern part of the CentralRhodopean district (Davidkovo and Laki) and deposits fromthe Eastern Rhodopes, compositions of fahlores from thestudied deposits have particular compositions (Fig. 9). Onthe As/(As+Sb) vs Ag/(Ag+Cu) diagram Petrovitsa samplesplot along a well-defined trend in the bottom part of thediagram, partially overlapping with data from the Laki de-posits (Fig. 9a). Fahlores from the Davidkovo ore field areexclusively of tetrahedrite compositions and show much

higher Ag content. Data from the Eastern Rhodopes plot alongthree trends one of which overlaps with the data fromGradishte deposit. Fahlore compositions from the GoliamPalas deposit in the northwestern part of the Madan ore fieldare with the highest Ag content. On the Cu*-Fe-Zn diagram(Fig. 9b), data from theMadan, Laki and Davidkovo ore fieldsdefine different trends. Compositions from Davidkovo andLaki plot in the upper part of the diagram, suggesting evenmore oxidized conditions of formation compared to theMadan deposits, due to the presence of Cu2+ in addition toFe3+ in the fahlore structure.

According to Spiridonov et al. (2005) and Sack (2005),fahlore precipitation in nature takes place at temperature be-tween 100° and 400 °C, but mostly in the 180–300 °C inter-val, and at pressures <4 Kbar. We were unable to measurefluid inclusions in minerals directly associated with thefahlores from the studied samples; thus, the temperature oftheir formation can be estimated based on existingmicrothermometry data on minerals which are pre-and post-dating the fahlores. Microthermometry of fluid inclusions inquartz from the main base-metal stage in these samples re-vealed Th of as high as 340–320 °C for the quartz-chalcopyrite association in Gradishte (Vassileva et al.2009b). The mineral relationships show that the fahlores arelater than the chalcopyrite and associated quartz crystals; theyformed at the end of the main ore stage. From the other hand,fahlores formed before sphalerite-3 (see Fig. 3e), which be-longs to the late carbonate stage and in which Bonev andKouzmanov (2002) reported Th of primary fluid inclusionsalong growth zones ranging from 240° to 200 °C. Thus,textural characteristics, mineral relationships and existing flu-id inclusion data suggest that tennantite-tetrahedritess atMadan precipitated in the late stages of mineralization attemperatures between 300 and 200 °C, from oxidizing fluids.

Fig. 9 Compositions of fahlores from the Madan Pb-Zn deposits com-pared to Laki and Davidkovo ore fields from the Central Rhodopeanbase-metal district and other polymetallic vein deposits from the EasternRhodopes and Osogovo: a As/(As+Sb) vs Ag/(Ag+Cu); b Cu-Fe-Zn

system. Data sources: Madan—same as in Fig. 8, Laki (Kolkovski et al.2001; Vangelova and Kolkovski 2007), Davidkovo (Marinova andKolkovski 1994), Eastern Rhodopes (Breskovska et al. 1985; Bogdanov1992), Osogovo (Bogdanov 1992)


According to the existing stable isotope data on the base-metal stage of the Madan Pb-Zn deposits, the ore-formingfluids have mixed magmatic-meteoric signatures and plotalong a well-defined mixing trend on a δD-δ18O diagram(Piperov and Penchev 1982; Bonev et al. 1993). Importantmeteoric fluid input during the late stages of mineralization atMadan can also be the reason for an increase of oxygenfugacity, as it has been discussed above.

Conclusions

Minerals of the tennantite-tetrahedrite solid solution serieswere systematically studied in vein-type ore bodies from theGradishte and Petrovitsa deposits from the central part of theMadan Pb-Zn ore field, in the southern part of the CentralRhodopean base-metal district. The minerals are the mostcommon sulfosalt constituents of the Madan Pb-Zn mineral-ization. Mineral relationships with the associated sulfidesrevealed that they belong to the late phases of the main base-metal stage. Although fahlores are associated intimately withthe main sulfides they are formed later than chalcopyrite,galena and sphalerite.

A wide range of compositions from pure tennantite toarsenian tetrahedrite is covered in Gradishte. The depositionof the tetrahedrite together with and shortly after the mainsulfide minerals in Petrovitsa indicates the predominant roleof Sb in the ore deposition compared to that of As. All thestudied fahlore minerals are zincian varieties with 1.61–1.94apfu Zn and low Fe-content. Minor silver incorporation occursonly in tetrahedrite crystals from Petrovitsa.

The presence of fahlores in the late hydrothermalmineralization suggests increased activity of Sb and Asin the fluids. Presence of excess-Cu, compensated byFe3+ in the structure indicates increased fO2 of the fluidduring fahlore precipitation. Oxidizing character of theore-forming fluids results in the formation of an oxi-dized mineral assemblage, consisting of hematite andepidote, during the late mineralization stages. Texturalcharacteristics, mineral relationships, and available fluidinclusion data suggest that fahlore minerals at Madanare late feature of the hydrothermal system, and precip-itated at temperatures between 300 and 200 °C.

Acknowledgments The work is supported by the projectBG051PO001-3.3.05–0001 “Science and business” in the frame of “De-velopment of the man resources” Program of the Bulgarian Ministry ofScience and Education, the SCOPES IZ73Z0-128089 and the SNF20021-127123/1 projects of the Swiss National Science Foundation. Dr.Elitsa Stefanova is gratefully acknowledged for the technical support andher help with the LA-ICP-MS analyses at the Geological Institute, BAS.Reviews by Associated Editor Anton Beran and Eugen Libowitzkysubstantially improved the quality of the manuscript.

References

Andrew CJ (2003) Europe’s base metal mining industry a status report.In: Kelly JG, Andrew CJ, Ashton JH, Boland MB, Earls G,Fusciardi L, Stanley C (eds.). Europe’s major base metal deposits,Irish Association for Economic Geology: 31–47

Atanassov V (1975) Argentian mercurian tetrahedrite, a new variety fromthe Chiprovtsi ore deposit, Western Stara Planina Mountains,Bulgaria. Miner Mag 40:233–237

Basu K, Bortnikov NS, Mookherjee A, Mozgova NN, Svintsov AV,Tsepin AI, Vrublevskaja ZV (1984) Rare minerals from theRajpura-Dariba, Rajasthan, India. V. The first recorded occurrenceof manganoan fahlore. N Jb Miner Abh 149:105–112

Bogdanov B (1961) Stages of mineralization, mineral paragenesis andzonality in Pb-Zn deposts in Madan and Nedelino ore districts. RevBulg Geol Soc 22(2):133–160, in Bulgarian

Bogdanov K (1992) Tetrahedrite-tennantite series from some ore depositsin Bulgaria. Annuaire de l’Universite de Sofia 83(1):71–85

Bogdanov K, Fillipov A (2001) Mineral chemistry and thermodynamicsof tetrahedrite-tennantite mineral series from the Eastern Rhodopes,Bulgaria. Annuaire de l’Universite de Sofia 91(1):109–116

Bonev IK (1973) Genesis of the oriented overgrowths and intergrowths inthe Madan ore region. Bull Geol Inst, Ser GeochemMineral PetrogrXXII:91–105, in Bulgarian

Bonev I (1982) Central rhodopes. Guide-Book 3, IMA-82, 13th GeneralMeeting, Varna, 71

Bonev IK, Boyce AJ, Fallick AE, Rice CM (1993) Stable isotope evidencefor the genesis of the Madan vein and replacement lead-zinc deposits,Central Rhodopes, Bulgaria. In: Fenoll Hach-Ali, Torres-Ruiz, Gervilla(eds.). Current Research in Geology Applied to Ore Deposits, 37–40

Bonev IK, Kouzmanov K (2002) Fluid inclusions in sphalerite as nega-tive crystals: A case study. Eur J Miner 14:607–620

Bonev IK, Piperov NB (1977) Ore deposition, boiling and vertical extendof the lead-zinc mineralization of theMadan district. Geol Balcanica7(4):27–42

Bonev IK, Vassileva RD, Zotov N, Kouzmanov K (2005) Manganilvaite,CaFe2+Fe3+(Mn, Fe2+)(Si2O7)O(OH), a new mineral in the ilvaitegroup, from Pb-Zn skarn deposits in the Rhodope Mts., Bulgaria.Can Mineral 43:1027–1042

Breskovska V (1988) The sulphosalts from the Madzharovo ore district.Annuaire de l’Universite de Sofia 78(1-II):294–320

Breskovska V, Tarkian M (1994) Compositional variation in Bi-bearingfahlores. N Jb Miner Mitth 5:230–240

Breskovska V, Mozgova N, Bortnikov N, Tzepin A (1984) Features ofchemical composition of faded ores in the lead-zinc deposits ofRhodopes (Bulgaria). Bull Acad Nauk SSSR 1:78–84, in Russian

Breskovska V, Mladenova V, Mozgova N, Tzepin A, Borodaev Y (1985)Sulphosalts from Zvesdel-Pcheloyad ore field, Eastern Rhodopes.Annuaire de l’Universite de Sofia 79(1):113–131, in Bulgarian withEnglish abstract

Buret Y (2012) Polymetallic mineralization of the Djurkovo deposit, Lakimining district, southern Bulgaria: Paragenesis and fluid evolution.MSc Thesis, University of Geneva

Burkhart-Baumann I (1984) Unusual tennantite from Quiruvilica, Peru.In: Sulfosalts: Observations and mineral descriptions, experimentsand applications (G. Moh, compiler). N Jb Miner Abh 150:25–64

Catchpole H, Kouzmanov K, Fontboté L (2012) Copper-excessstannoidite and tennantite-tetrahedrite as proxies for hydrothermalfluid evolution in a zoned cordilleran base metal district,Morococha, Central Peru. Can Mineral 50:719–743

Charlat M, Levy C (1974) Substitutions multiples dans la série tennantite-tdtraédrite. Soc franç Minéral Crist Bull 97:241–250

Charlat M, Levy C (1975) Influence des principales substitutions sur leparamétre cristallin dans la série tennantite-tdtraédrite. Soc françMinéral Crist Bull 98:152–158


Ciobanu CL, Cook NJ, Capraru N, Damian G, Cristea P (2005) Mineralassemblage from the vein salband at Sacarimb, goldenQuadrilateral,Romania: I. Sulphides and sulphosalts. Au-Ag-Te-Se deposits:IGCP Project 486, Kiten, Bulgaria. Geochem Mineral Petrol 43:47–55

Cook NJ, Ciobanu CL, Capraru N, Damian G, Cristea P (2005) Mineralassemblage from the vein salband at Sacarimb, GoldenQuadrilateral, Romania: II. Tellurides. Au-Ag-Te-Se deposits:IGCP Project 486, Kiten, Bulgaria. Geochem Mineral Petrol 43:56–63

Damian Gh, Damian F (2003)Mn-tetrahedrites in the Romanian territory.Acta Mineral Petrogr Abstr Ser. 1, Szeged, 24

Dimitrova D, Kerestedjian T, Petrova M, Ts I (2007) Compositionalvariation in the tetrahderite-tennantite fahlores and polybasite-pearceite series from the Chiprovtsi Ag-Pb deposit, northwesternBulgaria. Geol Surv Finland, Guide 53:39–44

Dragov P (1997) Fahlores in the Chiprovtsi Ag-Pb deposit (NWBalkan).Rev Bulg Geol Soc 58(1):3–14, in Bulgarian

Fadda S, Fiori M, Grillo SM (2005) Chemical variations in thetetrahedrite-tennantite minerals from the Furtei epithermal Au de-posit, Sardinia, Italy: Mineral zoning and ore fluids evolution. Au-Ag-Te-Se deposits: IGCP Project 486, Kiten, Bulgaria. GeochemMineral Petrol 43:79–84

Foit FF, Ulbricht ME (2001) Compositional variation in mercuriantetrahedrite-tennantite from the epithermal deposits of the Steensand Pueblo Mountains, Harney County, Oregon. Can Mineral 39:819–830

Ivanov Z, DimovD, Sarov S (2000) Structure of the central Rhodopes. In:Ivanov Z (ed.). Structure, alpine evolution andmineralizations of thecentral Rhodopes area (South Bulgaria). ABCD-GEODE Borovetz,Guide to Excursion B: 6–20

Johnson NE, Craig JR, Rimstidt JD (1986) Compositional trends intetrahedrite. Can Mineral 24:385–397

Johnson NE, Craig JR, Rimstidt JD (1987) Effect of substitutions on thecell dimension of tetrahderite. Can Mineral 25:237–244

Kaiser-Rohrmeier M, Handler R, von Quadt A, Heinrich C (2004)Hydrothermal Pb-Zn ore formation in the central Rhodopian dome,south Bulgaria: Review and new time constraints from Ar-Ar geo-chronology. Schweiz Miner Petrol Mitt 84:37–58

Kaiser-Rohrmeier M, von Quadt A, Driesner T, Heinrich CA, Handler R,Ovtcharova M, Ivanov Z, Petrov P, Sarov S, Peytcheva I (2013)Post-orogenic extension and hydrothermal ore formation: High-precision geochronology of the Central Rhodopian metamorphiccore complex (Bulgaria-Greece). Econ Geol 108:691–718

Kalogeropoulos SJ, Kilias SP, Arvanitidis ND (1996) Physicochemicalconditions of deposition and origin of carbonate-hosted base metalsulfide mineralization, Thermes ore field, Rhodope Massif, north-eastern Greece. Miner Depos 31:407–418

Kerestedjian T, Atanassova R, Bonev IK, Hristov V, Yurukova L,Arnaudov V, Hadjiev A, Apostolova I, Meshinev T (2000)Environmental impact of the mining activity—a complex investiga-tion in the Erma Reka valley, Madan ore district. Geochem MineralPetrol 37:111–126

Kharbish S, Götzinger M, Beran A (2007a) Compositional variations offahlore groupminerals fromAustria. Austrian J Earth Sci 100:44–52

Kharbish S, Libowitzky, Beran A (2007b) The effect of As-Sb substitu-tion in the Raman spectra of tetrahedrite-tennantite and pyrargyrite-proustite solid solutions. Eur J Miner 19:567–574

Kirov G, Mincheva-Stefanova J (1962) Mineralogische undgeochemische untersuchung der Blei-Zink-Lagerstätte “Borieva”in Erzbezirk Madan. Trav Geol Bulgarie, Ser Geochem Pol izk 3:129–178, in Bulgarian

Kolkovski B, Dobrev S (2000) Ore mineralization in the centralRhodopes. In: Ivanov Z (ed.). Sructure, Alpine Evolution andMineralizations of the Central Rhodopes Area (South Bulgaria).ABCD-GEODE Borovetz, Guide to Excursion B: 23–36

Kolkovski B, Bogdanov K, Petrov S (1980) Mineralogy, geochemistryand genetic features of the deposits along Goljam Palas-Ribnitsafault, Madan ore field. Annuaire de l’Universite de Sofia 74(1):97–153, in Bulgarian

Kolkovski B, Dobrev S, Petrov P, Manev D (1996) Geology, mineralogyand genesis of madan ore field. Proc Ann Meeting IGCP Project356(2):157–173

Kolkovski B, Marinova I, Nikovski V (2001) New data about the com-position and the genesis of strata bound base metal mineralizationsfrom Persenk ore field, Central Rhodopes. Annuaire de l’Universitede Sofia 94(1):171–192, in Bulgarian

Kostov I, Kostov R (1999) Crystal habits of minerals. Prof M DrinovAcad Publ House and Pensoft Publishers, Sofia

Kostova B, Pettke T, Driesner T, Petrov P, Heinrich C (2004) LA-ICP-MSstudy of fluid inclusions in quartz from the Yuzhna Petrovitsa deposit,Madan ore field, Bulgaria. Schweiz Miner Petrol Mitt 84:25–36

Kotseva B, Guillong M, Stefanova E, Piprov N (2011) LA-ICP-MSanalysis of single fluid inclusions in a quartz crystal (Madan oredistrict, Bulgaria). J Cheochem Explor 108:163–175

Kouzmanov K (2001). Genèse des concentrations en métaux de base etprécieux de Radka et Elshitsa (zone de Sredna Gora, Bulgarie): uneapproche par l’étude minéralogique, isotopique et des inclusionsfluides, Unpublished PhD Thesis, l’Université d’Orléans, in French

Kouzmanov K, Ramboz C, Bailly L, Bogdanov K (2004) Genesis of highsulphidation vinciennite-bearing Cu-As-Sb±(Au) assemblage fromthe Radka epithermal copper deposit, Bulgaria: evidence from min-eralogy and infrared microthermometry of enargite. CanMineral 42:1501–1521

Krasteva M (1977) Mineral thermometrical investigations on quartz andcarbonates from deposits along fault Ribnitsa-Golyam Palas. Ore-forming Processes and Mineral Deposits 7:23–37, in Bulgarian

Lynch JVG (1989) Large-scale hydrothermal zoning reflected in thetetrahedrite-freibergite solid solution, Keno Hill Ag-Pb-Zn district,Yukon. Can Mineral 27:383–400

Makovicky E, Forcher K, LottermoserW, Amthauer G (1990) The role ofFe2+ and Fe3+ in synthetic Fe-substituted tetrahedrite. Mineral Petrol43:73–81

Makovicky E, Karanovic L, Poleti D, Balić-Žunić T, Paar W (2005)Crystal structure of copper-rich unsubstituted tennantite, Cu12,5As4S13. Can Mineral 43:679–688

Malinov O (1987) Simultaneous deposition of zincian tetrahedrite andzincian tennantite in the lead-zinc ore deposit of Jučora and in theKavalci ore manifestation, Madan ore field. Geochem MineralPetrol 23:45–53, in Bulgarian

Marchev P, Kaiser-Rohrmeier M, Heinrich C, Ovtcharova M, von QuadtA, Raycheva R (2005) 2: Hydrothermal ore deposits related to post-orogenic extensional magmatism and core complex formation: TheRhodope Massif of Bulgaria and Greece. Ore Geol Rev 27:53–89

Marcoux E, Moëlo Y, Milési JP (1994) Vinciennite and Cu-excesstennantite from the Layo (Cu, Sn, As, Au) epithermal deposit(southern Peru). Mineral Petrol 51:21–36

Marinova I, Kolkovski B (1994) New data on mineralization sequenceand mineralogy of Davidkovo ore field, Central Rhodopes.Annuaire de l’Universite de Sofia 84:301–343, in Bulgarian

Meinert LD, Dipple GM, Nikolescu S (2005) World skarn deposits.Society of economic geologists, economic geology 100th anniver-sary volume: 299–336

Milev V, Stanev V, Ivanov V (1996) Mining production in Bulgaria1878–1995, statistical reference book. Zemia-93 Press, in Bulgarian

Miller JW, Craig JR (1983) Tetrahedrite-tennantite series compositionalvariations in the Cofer deposit, mineral district, Virginia. AmMineral 68:227–234

Mincheva-Stefanova J (1960) On epitaxic intregrowths of galena andtetrahedrite. Zap Vses Mineral Obshchest 89:213–219, in Russian

Mincheva-Stefanova J, Gorova M (1965) Mineralogie und geochemieder blei-zink-lagerstätte Gradiste im erzbezirk Madan. Trav Geol


Bulg, Ser Geochim Mineral Petrogr V:117–191, in Bulgarian withGerman abstract

Mincheva-Stefanova J, Gorova M, Pavlova M (1964) Zink-tetraedrit ausden blei-zink-lagerstätten im Erzbezirk Madan. Rev Bulg Geol Soc25:181–186, in Bulgarian

Mozgova NN, Tsepin AI (1983) The Fahlores. Nauka, Moskow, inRussian

Nickel EH (1992) Solid solutions in mineral nomenclature. Can Mineral30:231–234

Peytcheva I, Dimitrova D, Marchev P, Cherneva Z, Ganev V, Popov M(2009) LA-ICP-MS at the geological institute, bulgarian academy ofsciences—a powerful tool for the trace element and isotope studiesof rocks, minerals, soils, coal, water and archeological artifacts. ProcNational Conference Geosciences, Sofia, pp 19–20

Piperov NB, Penchev NP (1982) Deuterium content of the inclusionwater from hydrothermal galenas, Madan, Bulgaria: Preliminaryinvestigation. Scientific Communications 195–197

Plotinskaya OY, Rusinov VL, Kovalenker VA, Seltman R (2005)Oscillatroy zoning in goldfieldites as possible indicator of theirformation conditions. Au-Ag-Te-Se deposits: IGCP Project 486,Kiten, Bulgaria. Geochem Mineral Petrol 43:142–147

Plotinskaya OY, Grabezhev AI, Groznova EO, Seltmann R, Lehmann B(2013) The Late Paleozoic porphyry-epithermal spectrum of theBirgilda-Tomino ore cluster in the South Urals, Russia. J AsianEarth Sci. doi:10.1016/j.jseaes.2013.01.015

Radulova AS (1996) Chemical composition of chalcopyrite from Madanore district. Geochem Mineral Petrol 31:41–49

Sack RO (2005) Internally consistent database for sulfides and sulfosaltsin the system Ag2S-Cu2S-ZnS-FeS-Sb2S3-As2S3: Update. GeochimCosmochim Acta 69:1157–1164

Sack RO, Loucks RR (1985) Thermodynamic properties of tetrahedrite-tennantites: Constrains on the interdependence of the Ag↔Cu;Fe↔Zn, Cu↔Fe and As↔Sb exchange reactions. Am Mineral70:1270–1289

Spiridonov E, Maleev M, Kovachev V, Kulikova I, Nazmova G,Filimonov S (2005) Minerals of fahlore group: indicators of oregenesis. Proc Jubilee Intern Conf Bulg Geol Soc 80th Ann: 79–82

Strashimorov S, Georgiev V, Mitov V (1985) Mineralothermometricstudies in Batanci, Krushev dol, Borieva and Gradishte deposits(Madan ore region). Annual of the Higher Institute of Mining andGeology 31(2):67–77

Tarkian M, Breskovska V (1990) Arsenic minerals and their geneticsignificance in the Madjarovo ore field, Eastern Rhodope,Bulgaria. N Jb Miner Mitth 10:433–442

TarkianM, Breskovska V (1995) Mineralogy and fluid inclusion study ofthe Zidarovo copper polymetallic deposit, eastern Bulgaria. N JbMiner Abh 168:283–298

Tzvetanov R (1975) Hydrothermal metasomatites in the Caraaliev dol-Petrovitza fault of the Madan ore field. Annuaire de l’Universite deSofia 67(1):295–308, in Bulgarian with English abstract

Vangelova V, Kolkovski B (2007) Mineralogy, geochemistry and geneticfeatures of deposit Chetroka, Laki ore field. Annuaire de

l’Universite de Sofia 100(1):97–129, in Bulgarian with Englishabstract

Vassileva RD (2004) Compositional variation in the manganoanclinopyroxenes from the Central Rhodopian skarn-Pb-Zn deposits,Bulgaria. Proc. 5th Intern Symp Eastern Mediterranean Geology,Thessaloniki, pp 1469–1472

Vassileva RD, Bonev IK (2001) Manganoan amphiboles from the skarn-ore Pb-Zn deposits in the Madan district, Central Rhodope Mts.,Bulgaria. Geochem Mineral Petrol 38:45–53

Vassileva RD, Bonev IK (2002) Hydrothermal manganoan chamositefrom the vein and replacement Pb-Zn ore deposits, Madan district,Bulgaria. Geochem Mineral Petrol 39:81–93

Vassileva RD, Bonev IK (2003) Retrograde alterations of manganoanskarns in the Madan Pb-Zn deposits, South Bulgaria. In: Eliopoulos(ed) Mineral exploration and sustainable development. Millpress,Rotterdam, pp 403–406

Vassileva RD, Atanassova R (2009) Zincian tetrahedrite from the depositof Yuzhna Petrovitsa, Madan ore field. Proc National ConferenceGeosciences, Sofia, pp 31–32

Vassileva RD, Atanassova R, Bonev IK (2009a) A review of themorphological varieties of ore bodies in the Madan Pb-Zndeposits, Central Rhodopes, Bulgaria. Geochem MineralPetrol 47:31–49

Vassileva RD, Atanassova R, Kouzmanov K, Kerestedjian T (2009b)Madan Pb-Zn deposits, Central Rhodopes, Bulgaria: Mineralizationstages and fluid inclusion microthermometry. XXECROFI meeting,Granada, pp 271–272

Vassileva RD, Atanassova R, Stefanova E, Marchev P, Peytcheva I,Kouzmanov K (2010) Minor and trace element content of sulphidesfrom the Madan polymetallic deposits, Central Rhodopes: A LA-ICP-MS study. Proc National Conference Geosciences, Sofia, pp52–53

Whitney DL, Evans BW (2010) Abbreviations for names of rock-formingminerals. Am Mineral 95:185–187

Wu I, Petersen U (1977) Geochemistry of tetrahedrite and mineral zoningat Casapalca, Peru. Economic Geology and the Bulletin of theSociety of Economic Geologists 72 (6) Mineral deposits in theSouth American Cordillera: 993–1016

Zotov AV, Kudrin AV, Levin KA, Shikina ND, Var’yash LN (1995)Experimental studies of the solubility and complexing of selectedore elements (Au, Ag, Cu, Mo, As, Sb, Hg) in aqueous solutions. In:Shmulovich KI, Yardley BWD, Gonchar GG (eds) Fluids in thecrust—Equilibrium and transport properties. Chapman & Hall,London, pp 95–137

Zotov AV, Shikina ND, Akinfiev NN (2003) Thermodynamicproperties of the Sb (III) hydroxide complex Sb(OH)3(aq) athydrothermal conditions. Geochim Cosmochim Acta 67:1821–1836

Zotov N, Kockelmann W, Jacobsen S, Mitov I, Paneva D, Vassileva RD,Bonev IK (2005) Structure and cation ordering in manganilvaite: Acombined X-ray diffraction, Neutron diffraction and Mössbauerstudy. Can Mineral 43:1043–1053


http://dx.doi.org/10.1016/j.jseaes.2013.01.015

Date post:	23-Dec-2016
Category:	Documents
Upload:	kalin
View:	219 times
Download:	5 times

Tennantite-tetrahedrite series from the Madan Pb-Zn deposits, Central Rhodopes, Bulgaria

Documents