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(1)AGH University of Science and Technology Faculty of Geology, Geophysics and Environmental Protection Economic Geology Department. PhD Thesis. MINERALOGICAL AND GEOCHEMICAL DIVERSITY WITHIN THE STAN TERG DEPOSIT, KOSOVO. Author: Joanna Kołodziejczyk, M.Sc.. Thesis supervisor: Jaroslav Pršek, Ph.D.. Kraków 2016.

(2) PREFACE Lead and zinc deposits belong to what are referred to as base metal deposits. Pb and Zn are often accompanied by other commodities in high concentrations, such as silver or copper, as well as some elements of economic value, like In, Ge, Ga, but occurring in trace concentrations. The mineralogical composition of the ore and its geochemical properties are suggested to be related to the origin of the deposit, hydrothermal alterations, conditions of ore minerals precipitation. Lead and zinc ores are widespread in the Earth and may form in different geological environments. Hydrothermal ore deposits occur as a result of deposition from hot aqueous solutions, which may have had a magmatic, metamorphic, surface or other source. They occur in a wide range of solution temperatures: 50-700 ˚C. The hydrothermal fluids consist mostly of saline water. Hydrothermal ore deposits are relatively small in volume but are characterized with wide range of minerals, mostly sulfides, sulphosalts, and oxides. Hydrothermal deposits vary greatly depending on the source of solutions, source(s) of metals and sulphur, mechanism of transport, and deposition. Also, pressure, temperature, and host rock composition are important factors that contribute to what kind of deposit is ultimately formed. Hydrothermal deposits formed in the highest temperatures are characterized with metasomatic products of alteration by hydrothermal fluids. Such deposits, called skarns are formed in some cases by the replacement of carbonate wall rocks adjacent to an igneous intrusion. Hydrothermal Pb-Zn deposits, for example, occur mainly in sedimentary (carbonates) or volcanic rocks. Pb-Zn deposits may also form through surface processes. In this group belong sedimentary-exhalative deposits (SEDEX), or volcanic-hosted massive sulfide deposits (VHMS). They are the result of exhalations of hydrothermal solutions at the surface under marine conditions at the sea floor/seawater interface. These deposits usually produce stratiform orebodies. The tectonic setting of such conditions are primarily rift valleys. Depending on the exhalation position with respect to the rift valley, these deposits are diverse in terms of their elemental composition but in general are mineralogically simple and uniform in texture and composition. To this group of deposits belongs Mount Isa in Australia, Rio Tinto in Spain, and Kuroko in Japan. Finally, weathering processes can lead to “leaching” from rocks and previously existing sulfide ore deposits leaving a concentrate of sulfates in the residual material. These deposits are not commonly extracted but in recent years they are an area of interest for many II.

(3) exploration companies. The leaching of valuable elements from the upper part of deposit allows them to move and precipitate at depth and produce higher concentration. This often causes the strong zonality, with strong marked gold-silver zone in the central part of the deposit. The aim of this Ph.D. thesis research project was to study the diversity and distribution of base metals found within the skarn Pb-Zn-Ag hydrothermal mineral system at the Stan Terg deposit in Kosovo, in southeastern Europe. It is of great importance to know the amount and distribution of minor chemical elements that may influence the refining process, and to determine if those elements may be extracted from the ore. This work is based on the joint cooperation between the AGH University of Science and Technology in Kraków, Poland, and the Trepça Mining Company, Kosovo. The ore deposits of Trepça can potentially contribute to the economy in the developing country of Kosovo. The mineral wealth is of great importance to the regional development, since the mineral deposits occur across the country. Polymetallic ores in Kosovo have been extracted from ancient times, throughout the centuries, and during the twentieth century were one of most important Pb-Zn occurrences in Europe, and continue to be extracted. The main objectives of this study is: (i) mineralogical and geochemical reexamination of Pb-Zn ores from the Stan Terg deposit using modern analytical techniques, EPMA and LA-ICPMS; (ii) determining where the minor and trace elements reside in the deposit; and (iii) determining the distribution of minor and trace element within the main ore minerals.. III.

(4) ACKNOWLEDGEMENTS This project was supported financially in part by the Society of Economic Geology Foundation in 2014 and 2015, as well as by the Faculty of Geology, Geophysics and Environmental Protection at the AGH University of Science and Technology (AGH-UST) in Kraków, Poland. I am grateful to Jaroslav Pršek for his encouragement and guidance throughout my academic career. My gratifying thanks are also extended to Vasilios Melfos, and Panagiotis Voudouris for their help in data analysis. I would like to express my sincere gratitude to the laboratories at the AGH-UST, the Geological Institute of the Bulgarian Academy of Sciences (Sofia, Bulgaria), and the University of Adelaide (Adelaide, Australia). My sincere thanks also go to Jean Féraud who helped in the literature search, and most of all thanks to John M. Hanchar for the English corrections of this manuscript and many fruitful discussions about the analytical methods used and analyses discussed in this thesis. My special thanks go to the current Trepça Mining Company managers, Ferat Shala, Halil Qela, and Ahmet Tmava, and the director of the Stan Terg mine, Qazim Jashari. I am particularly grateful for the assistance during field work provided by the staff of Stan Terg mine including Feriz Maliqi, Safet Peci, Avdullah Berisha, Refik Veseli, Xhemajl Tupella, Behxhet Vinarci, Hakif Beqiri, Shyqyri Sadiku, and Burim Asllani.. IV.

(5) ABSTRACT Detailed mineralogical and geochemical analyses were done on the samples from various mineralization styles collected from the Stan Terg Pb-Zn mine, Kosovo. The application of electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) allowed for the determination for obtaining major, minor, and trace element chemical compositions of selected mineral phases, including submicroscopic inclusions, and at very low concentrations (as low as around 1 ppm) that can be linked in the crystal chemistry of the main sulphides. Galena is the main host of Bi, Ag, Au, Sb, Sn and Tl, sphalerite hosts Sn, In, Ga, Cd and Hg, pyrite hosts Co and Ni, arsenopyrite Ge, Au, and Co, chalcopyrite Ag, Ge, Cd, Sn, Ni, tetrahedrite Ag and Hg. Pyrrhotite does not incorporate significant minor or trace elements in its structure. Several Bi-bearing sulphosalts, previously unknown in Kosovo, have been identified in the Stan Terg deposit using the EPMA analyses done on samples associated with skarn mineral paragenesis. Tetradymite group minerals, mainly ikunolite and babkinite, show low degree of S and Se substitution and higher concentrations of Pb for Bi. Joséite-A is the first Te mineral described from this locality. Lillianite homologues include lillianite (N=4) and heyrovskýite (N=7) with a low degree of AgBi for 2Pb2+ substitution, average x = 0.21 and 0.17, respectively. Izoklakeite, the fourth member of the kobellite homologous series with average Sb/(Sb+Bi) ratio about 0.43, is also described. Other Bi-bearing minerals identified include cannizzarite, cosalite, native bismuth, and bismuthinite. All minerals described are associated with galena with elevated Bi and Ag contents (0.02 Bi+Ag apfu). The presence of native gold is spatially related with Bi mineralization. The physico-forming conditions for bismuth-related mineralization suggests temperatures between 350-400°C. Investigation of sulphotelluride phases indicate a presence of joséite-A, joséite-B and two unidentified minerals: phase A, with chemical formula (Bi,Pb)2(TeS)2 , and phase B, with chemical formula (Bi,Pb)2.5Te1.5S1.5. Sulphotellurides occur in association with cosalite, Sbrich lillianite, kobellite homologeus series and Bi-rich jamesonite. In situ analyses of the tellurides or the accompanying sulphosalts do not reveal significant concentrations of Ag or Au, and Ag tellurides have not been found in the Stan Terg deposit. The hydrothermal fluids were likely depleted in precious metals limiting the precipitation of Au and Ag from this hydrothermal system. Also reported are results from recently discovered Ag mineral association in the Stan Terg deposit, located in the Vardar Zone (in the northern Kosovo). The mineralization described comprises pyrargyrite, freieslebenite, high-Ag bearing tetrahedrite, freibergite and native compounds (electrum, native Ag, native Sb). Ag minerals occur in vugs and cracks in massive galena ore that suggests these are the latest precipitated minerals in the deposit. The chemical composition of those minerals was determined with the EPMA. Freibergite from the Stan Terg deposit is chemically zoned and contains between 13.91-20.28 at. % of Ag. High Ag solutions are also indicated by relatively high Ag content in electrum, which is between 47.02 and 73.19 at. % of Ag. The Ag association is thought to be an epithermal equivalent of precious metal mineralization which could be located in the external part of the Stan Terg hydrothermal system. This association occurs at low temperatures, below 200˚C. The Ag minerals may be part of an epithermal vein system from the external part of the Stan Terg deposit. Similarly to other known Pb-Zn-Ag hydrothermal systems, silver association is related to formation of the rhodochrosite banded ore and Ag-Au-Sb±Hg dominated mineralization. Tin is a common minor element in the hydrothermal base metal deposits in Kosovo. Stannite commonly occurs at Stan Terg deposit in small amounts in association with V.

(6) sphalerite, chalcopyrite, galena, pyrite and pyrrhotite. Sphalerite from Stan Terg, commonly overgrown by stannite contains the lowest Sn content (few ppm) and may have been precipitated before Sn-enrichment from the hydrothermal fluids. The highest value of Sn (520 ppm) in Stan Terg sphalerite was obtained in close proximity to a stannite rim, and indicates a rapid increase of Sn concentration in the later hydrothermal fluids. Stannite-sphalerite geothermometry revealed the following ore-forming temperatures 240° to 390 °C for Stan Terg. Sphalerite, chalcopyrite, and stannite, precipitated simultaneously during cooling from reduced hydrothermal fluids and under low-sulfidation fluid states. Fluctuations in physicochemical fluid conditions are revealed by the presence of stannite group minerals along growth zones in sphalerite crystals and may be related to short interval of magmatic pulses during ore deposition. The results obtained from in situ detailed geochemical analyses of the main sulphides occurring in the deposit and their paragenetic relationship with the other minerals are a foundation for a new paragenetic sequence model for the ore mineralization at the Stan Terg deposit. At least four generations of galena and sphalerite, three generations of pyrrhotite, arsenopyrite, and chalcopyrite, and at least five groups of tetrahedrite were identified. The first mineral generation may be related to precipitation in a matrix within the limestone breccias near by central pipe, and comprises galena, Bi-minerals, arsenopyrite, pyrite, native gold and chalcopyrite. The skarn-related mineralization, occurring in association with gangue skarn minerals (like hedenbergite, ilvaite, garnet) comprises galena, at least two Bi-associations (one with sulphotellurides), pyrite, two pyrrhotite generations, sphalerite and less commonly tennantite and As-rich tetrahedrite. During the main hydrothermal replacement phase of precipitation, most of the mineralization occurred. This consists of the main phases hosting Pb and Zn mineralization, include galena, arsenopyrite, pyrite, chalcopyrite, pyrrhotite, and at least two generations of sphalerite and tetrahedrite. The period of mineralization with Cu is postdates the main Pb and Zn stage, and comprises galena overgrown by bournonite, and younger generations of arsenopyrite, pyrite, chalcopyrite, sphalerite, stannite, and tetrahedrite. Ag mineralization comprises native gold/electrum (with high Ag content), Ag minerals, Ag-rich tetrahedrite, freibergite and chalcopyrite. The youngest ore mineral is boulangerite, occurring primarily in the oligonite zone, but also occurs covering most of minerals precipitating in cavities. There are few secondary minerals, since the supergenic stage is weakly developed even at the surface. Minerals hosted in the vein and brecciated style of mineralization, have similar geochemical signature as ore minerals in skarn-related and primary replacement mineralization, which suggests that these mineralizations have precipitated during the whole episode of ore deposition.. VI.

(7) TABLE OF CONTENTS PREFACE .............................................................................................................................................................. II ACKNOWLEDGEMENTS .................................................................................................................................. IV ABSTRACT ........................................................................................................................................................... V TABLE OF CONTENTS .....................................................................................................................................VII 1.. Introduction .................................................................................................................................................. 1 1.1 General model for Pb-Zn metasomatic-hydrothermal deposits worldwide ............................................... 1 1.2 Minor and trace elements in Pb-Zn deposits ............................................................................................. 5 1.3 Pb-Zn metasomatic-hydrothermal deposits in the Balkan area and in the Vardar zone .......................... 11 1.4 Geological setting of the Stan Terg deposit ............................................................................................ 15 1.5 Previously mineralogical and geochemical study on the Stan Terg deposit............................................ 19 1.6 Objective of the study and problem statement ........................................................................................ 22 2. Methods ...................................................................................................................................................... 24 2.1 Sampling strategy .................................................................................................................................... 24 2.2 Mineral identification: Microscopic observations ................................................................................... 25 2.3 Geochemical analyses: EPMA and LA-ICPMS ...................................................................................... 25 2.3.1 Electron Probe Microanalyzer (EPMA) ............................................................................................ 25 2.3.2 Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) .............................. 27 3. Results ......................................................................................................................................................... 30 3.1 Mineralization styles ............................................................................................................................... 30 3.1.1 Skarn-related mineralization ............................................................................................................. 31 3.1.2 Primary replacement ore and karst fillings ........................................................................................ 33 3.1.3 Rhodochrosite banded ore and oligonite ore ..................................................................................... 33 3.1.4 Breccia-style ore mineralization ........................................................................................................ 36 3.1.5 Nests and veinlets .............................................................................................................................. 37 3.2 Ore composition in the investigated parts of the deposit......................................................................... 38 3.3 Main ore minerals composition ............................................................................................................... 41 3.3.1. Galena .............................................................................................................................................. 41 3.3.2. Sphalerite.......................................................................................................................................... 57 3.3.3. Pyrite ................................................................................................................................................ 71 3.3.4. Pyrrhotite .......................................................................................................................................... 84 3.3.5. Arsenopyrite ..................................................................................................................................... 90 3.3.6. Chalcopyrite ................................................................................................................................... 101 3.3.7. Tetrahedrite group minerals ........................................................................................................... 113 3.3.8. Ag-mineral association ................................................................................................................... 120 3.3.9. Bismuth and telluride mineral associations .................................................................................... 127 3.3.10. Sn-mineral association ................................................................................................................. 153 3.3.11. Other sulphosalts .......................................................................................................................... 155 3.3.12. Native elements ............................................................................................................................ 157 4. Discussion ................................................................................................................................................. 159 4.1. Comparison of EPMA and LA-ICPMS data ......................................................................................... 159 4.2 Spatial distribution of minor and trace elements in the Stan Terg hydrothermal system ...................... 161 4.3 Geologic significance of tin .................................................................................................................. 172 4.4 Bi-assemblages as an indicator of the high temperature characteristics of the Stan Terg ore ............... 180 4.5 Epithermal mineralization with Ag-assembages ................................................................................... 190 4.6 Precipitation sequence at the Stan Terg mineral system ....................................................................... 193 5. Conclusions .................................................................................................................................................... 196 6. References ...................................................................................................................................................... 199 LIST OF FIGURES ............................................................................................................................................. 212 LIST OF TABLES .............................................................................................................................................. 219 LIST OF APPENDICES ..................................................................................................................................... 219. VII.

(8) 1. INTRODUCTION 1.1. GENERAL. MODEL. FOR. PB-ZN. METASOMATIC-HYDROTHERMAL. DEPOSITS. WORLDWIDE. Metasomatic-hydrothermal deposits include skarn and polymetallic replacement deposits. They are genetically related to magmas intruding into sedimentary rocks, very often related to porphyry intrusions. The system of fluid migration and spatial distribution of the mineralization is similar for these kinds of deposits globally. In many mineral districts there are several types of hydrothermal deposits linked in one system. The general model of magmatic and volcanic related deposits was suggested by Plumlee et al. (1999), and is shown in Figure 1. In the close vicinity of magmatic stock and related dykes intruding a sedimentary sequence with carbonate layers, the skarn alteration and associated ore can be observed. With magmatic intrusions porphyry-type mineralization may also occur. In the distal regions in the vicinity of skarn deposits replacement ores are also often observed. The orebodies of the latter kind may have chimney- or manto-like shapes. The system may commonly contain brecciated ore of hydrothermal origin. Polymetallic veins cutting surrounding sedimentary rocks occur mainly in the distal parts of the system. Skarns as well as replacement ore deposits are thought to occur in the intermediate zone between porphyry deposits in the center of mineral district, and polymetallic veins in the distal parts. Skarn ores are thought to be relatively minor in districts with primary replacement deposits (Einaudi and Burt, 1982; Johnson and Norton, 1985; Mainert, 1992; Hammarstrom et al., 1995; Plumlee et al., 1999). Hydrothermal systems have commonly typical zonation with Cu enriched in the deeper porphyry and skarn deposits, and Pb and Zn mineralization dominating in polymetallic veins and replacement deposits. Skarns are metamorphic rocks composed of calcium-iron-magnesium-manganesealuminum silicate minerals. The formation of skarns is caused by replacement of carbonates during contact or regional metamorphism and metasomatism caused by the infiltration of hydrothermasl fluids (Baker et al., 2004). Skarns may be barren or host ore mineralization in massive, stratiform, vein, or disseminated form. In terms of commodities, we can distinguish Cu, Fe, W, Sn and Pb-Zn skarns (Einaudi and Burt, 1982; Mainert, 1992). Crystals vary in size, from fine to very coarse. The deposition of sulphide minerals and gold generally takes place during late, retrograde alteration within zones characterized by hydrous calc-silicates, 1.

(9) like diopside-hedenbergite, wollastonite, tremolite-actinolite, and garnets (Hammarstrom et al., 1995). The main ore minerals in the Pb-Zn skarns include pyrite, magnetite, chalcopyrite, sphalerite, and galena, and are commonly related to the carbonate-rich alteration assemblages (Plumlee et al., 1999). Replacement deposits consist of massive lenses (mantos), pipes (chimneys), mineralized breccias or veins of iron, lead, zinc, and copper sulphide minerals (Figure 1) hosted by and replaced sedimentary rocks (e.g., dolomite, limestone, sandstone, and shale). Disseminated mineralization is common. The origin of sediment-hosted ore is commonly intimately associated with igneous intrusions in the sedimentary rocks. Intrusions have intermediate- to felsic-composition and occur as igneous stocks, dikes, and sills. Replacement deposits are commonly polymetallic and are characterized by high concentrations of Pb, Zn, Cu, Au, Ag, Mo, As, Bi, and Sb (Burt, 1982; Einaudi and Burt, 1982; Plumlee et al., 1995).. F IGURE 1. G ENERAL. MODEL FOR GEOLOGIC SETTING OF HIGH - TEMPERATURE , CARBONATE - HOSTED AN D. RELATED SKARN MINERALIZATION ( MODIFIED AFTER. P LUMLEE. ET ALL .. 1999).. Polymetallic replacement deposits may be Pb-Zn-rich or Cu- (± Au-) rich. Minerals are typically medium to coarse grained and have textures from euhedral to massive interlocking grains. The main ore minerals are Fe-rich sphalerite, galena, pyrite, marcasite, chalcopyrite, argentite, tetrahedrite, enargite, digenite, and native Au, whereas the main. 2.

(10) gangue are quartz and carbonate minerals (Einaudi and Burt, 1982; Mainert, 1992; Plumlee et al., 1995). Carbonate replacement deposits may contain a single, massive orebody or several orebodies related to structural features that control fluid movement (e.g., fractures, fold limbs, karst cavities). Most replacement deposits are zoned and copper-gold ore is often proximal to intrusions, whereas Pb-Zn-Ag ore is laterally and vertically distal to intrusions. Hence, chalcopyrite, enargite, and native gold have higher grades in replacement deposits that are close to the igneous intrusions. Sometimes laterally (and also vertically) gradation from Cu-Au ore into Pb-Zn-Ag may be observed. In some districts, a distal Mn-enriched zone was distinguished. It has been reported that higher Pb and Zn contents are associated with porphyry-Mo deposits, than those that are associated with porphyry-Cu deposits (Burt, 1982; Einaudi and Burt, 1982; Plumlee et al., 1995; Plumlee et al., 1999). Within the host carbonates, alteration including recrystallization, dolomitization, or bleaching (e.g., color changes, production of aureoles) are sometimes present. Alteration to silica-rich jasperoid is known from several districts. If the mineralization is hosted within volcanic rocks, they may be altered to quartz-sericite-pyrite and quartz-clay (argillic) assemblages that grade into distal propylitic (e.g., epidote, chlorite, pyrite, carbonate) alteration assemblages (Mainert, 1992; Plumlee et al., 1999). Often, polymetallic replacement deposits are associated with skarn deposits. Hence, it is not always apparent to distinguish these kinds of deposits separately. Host carbonate rocks are replaced by calc-silicates (e.g., epidote, amphibole, garnet, and pyroxene) as well as by iron oxide mineral assemblages (Einaudi and Burt, 1982; Mainert, 1992; Plumlee et al., 1995). Skarns are often present close to plutons, in continental margin, syn- to late-orogenic tectonic settings such as those exposed in Canada (British Columbia), Peru, Japan, and the western Cordillera of the United States and Mexico (Plumlee et al., 1999). Hydrothermal systems occur in belts that have undergone moderate deformation and have been intruded by small plutons. Solutions are emanating from volcanic centers. Hence, these deposits are often found close to the old calderas (Morris, 1986). Metasomatic-hydrothermal deposits reveal great variations in terms of age, geometry of orebodies, mineral composition, zonation, alteration, and factors controlling migration of hydrothermal fluids. The physico-chemical conditions of ore precipitation vary over a wide range (Titley, 1993). Complex hydrothermal systems occur in numerous metallogenic provinces throught the world. Some of the best studied examples are Leadville and Gilman 3.

(11) (Colorado, USA), Santa Eulalia, Naica, and La Encantada (Mexico), and Cerro de Pasco and Morococha (Peru) (e.g., Plumlee et al., 1999). In Europe, Pb-Zn deposits of metasomatichydrothermal connected with vocanic-magmatic systems are concentrated in the Balkan Peninsula and continue eastward with some of Pb-Zn deposits occurring in Turkey. Several polymetallic deposits and occurrences of various type ores are well-known from Freiberg (Germany), Holly Cross Mountains (Poland), Romania, Ukraine and central Slovakia (e.g, Ciobanu et al, 2000, 2006; Plotinskaya et al., 2009; Seifert and Sandmann, 2006). They are of mostly of historical importance and not currently mined.. 4.

(12) 1.2. MINOR AND TRACE ELEMENTS IN PB-ZN DEPOSITS Iron is widespread element commonly occurring in all type of metasomatic-. hydrothermal deposits as primary sulphides, including pyrite, marcasite, pyrrhotite, arsenopyrite, and chalcopyrite. In the sphalerite structure, Fe concentrations may reach above 15 wt. % (Cook et al., 2009). Iron contents may vary significantly between deposit types, and may be used to estimate temperatures of minerals precipitation (e.g., Scott and Barens, 1971). Copper is commonly related to porphyry style of mineralization. It is also common in high temperature hydrothermal solutions in skarn deposits, where it occurs as primary Cu-minerals (e.g., bornite, chalcopyrite). Cu is thought to be incorporated only in limited quantities in the sphalerite structure, and more commonly Cu is present in the form of chalcopyrite blebs of up to few μm within sphalerite crystals (Cook et al., 2009), and their origin were disscussed to be the result of exsolution, or secondary replacement (e.g., Barton and Bethke, 1987; Bortnikov, 1991). Possible copper may be incorporated in the structure of sphalerite by couple substitution with In, Ag and Sn (Cook et al., 2009). Similarly, the presence of Cu in the galena structure is limited, and is supposed to be involved through a couple substitutions with Ag (George et al., 2015). Antimony occurs in numerous phases in Pb-Zn deposits, including Pb-Sb sulphosalts, Ag-Sb sulphosalts, and tetrahedrite. It is also an important trace element in galena (George at al., 2015) where its concentrations may vary from few ppm up to over 3,000 ppm. Radosavljević et al. (2015) reported up to 16,000 ppm of Sb in sphalerite from the Podrinje Metallogenic District, in Bosnia and Herzegovina. In other sulphides it is less common, and mostly occurs as inclusions of Sb minerals (e.g., boulangerite, falcmanite, jamesonite, bournonite). Arsenic is commonly present as löllingite, arsenopyrite, tennantite, realgar, enargite in numerous hydrothermal Pb-Zn deposits. It is not common in sphalerite, and it is rarely reported (Cook et al., 2009). Arsenic is common minor element in pyrite. As-enriched zones in pyrite are thought to be enriched in gold (Deol et al., 2012). Bismuth is one of the most mineralogically diverse element in nature (Christy, 2015), and can be found in Pb-Zn, W, Sn, Cu, Mo and Au deposits of magmatic-hydrothermal origin genetically associated with granitoids (e.g., greisen, skarn-carbonate replacement, porphyryepithermal, reduced intrusion-related) and also in volcanogenic massive sulphide (VMS) and orogenic-type of mineralization (Marcoux et al., 1996; Cook et al., 2009; Yokoro and 5.

(13) Nakashima, 2010) in the form of various primary minerals (e.g., native bismuth, bismuth sulfosalts and bismuth chalcogenides [Cook et al., 2007a,b; Moëlo et al., 2008]). Bismuth may indicate the presence of the precious metal ore formation in a deposit, which in turn may help with understanding the trace element distribution within the deposit. Bismuth is commonly incorporated in the galena structure via the coupled substitution Ag+ + (Bi,Sb)3+ ↔ 2Pb2+ (Chutas et al., 2008; Renock and Becker, 2011, George et al., 2015). Silver minerals are common ore minerals in primarily epithermal vein systems, but can be found also in skarn-, sedimentary-exhalative-, sediment-hosted-, porphyry-types of mineralization (e.g., Pearson et al., 1988; Grossou-Valta et al., 1990; Püttmann et al., 1991; Höller and Gandhi, 1995; Schalamuk et al., 1997; Zeng et al., 2000; Cheilletz et al., 2002; Shalaby et al., 2004; Seifert and Sandmann, 2006). The most common primary Ag sulphide minerals in epithermal systems are pyrargyrite, stephanite, proustite, argentite and/or native silver. Various groups of Ag-Pb-Bi(Sb) sulphosalts may also precipitate in high temperature conditions. Silver as a trace element may be found mostly in galena, where it is involved by the lillianite type of coupled substitution, Ag+ + (Bi,Sb)3+ ↔ 2Pb2+. Silver may be incorporated in relatively small amounts in the sphalerite structure, up to 100 pmm, and higher concentrations usually are related to submicroscopic inclusions of Ag-minerals (Taylor and Radtke 1969; Cook et al., 2009). Silver mineralization was reported in numerous occurrences in Balkan region (e.g., in the Podrinje Metallogenic District (Bosnia and Herzegovina), mainly from Srebrenica where Ag–bearing tetrahedrite, stephanite, polybasite, pyrargyrite, argyrodite and native silver have been described (Radosavljević et al., 2016). In the Zletovo mining district (Macedonia), freibergite, proustite, and pyrargyrite occur during sulphosalt paragenesis (Serafimovski et al., 2006). In the territory of Kosovo, pyrargyrite was reported by Smejkal and Rakić (1957) and Smejkal (1960) and, in the Stan Terg, Hajvalia, Kizhnica and Kopaonik deposits. Berjaktarevic (1995) described the “Glama silver” prospect, near Gjilan, with base metal ores with increased Ag, Au, and Sn contents. Tin is an economically important element occurring in high concentrations in porphyry, skarn, greisen, or polymetallic vein-type deposits (Kesler and Wilkinson, 2015). The most widespread Sn mineral is an Sn-oxide, cassiterite, but Sn can also commonly occur as sulfides (e.g.,. stannite,. kestërite,. mawsonite),. or. sulfosalts. (e.g.,. cylindrite,. franckeite).. Tin mineralization has been reported from various deposits globally, including Sn-Te-Bi-Sb polymetallic veins in Japan (Ishibashi, 1952), polymetallic veins in Kutná Hora (Czech republic) (Novák et al., 1962), granite-related Sn-mineralization at Mount Wellington (Cornwall, Great Britain) (Kettaneh and Badham, 1978), VMS-type deposit of Neves Corvo 6.

(14) (Portugal) (Benzaazoua at al., 2003), the CSA Cu-Pb-Zn deposit in Australia (Brill, 1989), Sn-As-Zn-Ag vein in the Besshi deposit, Japan (Kase, 1988), Bolivian tin belt (Sugaki and Kitakaze, 1988) and many others elsewhere. Petruk (1973) found thiostannates (stannite, kësterite, stannoidite, mawsonite) in Brunswick Tin Mines, New Brunswick, Canada. Stannite and kësterite were considered as important accessory minerals in the transitional Zn-Cu and distal Pb-Zn-Ag rich zones in Morococha district, Peru, by Catchpole et al. (2012). Tin minerals coexists commonly with sphalerite and they may form a limited solid solution series (Oen, 1980). Commonly Sn occurs as minute Sn minerals inclusions in sphalerite, and there is limited data about higher concentrations of Sn in sphalerite structure (Benzaazoua et al., 2003). Polymetallic epithermal high-intermediate sulfidation veins-type Au-Ag deposits in northeastern Greece, contain Sn-bearing phases (e.g., stannite, kestërite, mohite, kuramite, colusite, etc.) in association with tellurides and Bi-sulfosalts-sulfotellurides (Voudouris et al., 2011; 2013; Repstock et al., 2015). Zarić et al. (2000) described greisen-type mineralization with cassiterite, and hydrothermally overprinted with stannite, kësterite, and ferrokësterite with in some cases high Sn contents in sphalerite (up to 0.3 wt. %) in the Srebrenica ore field within the Vardar Zone. Manganese is common element in hydrothermal deposits, and occurs primarily in carbonates accompanying the primary ore mineralization (e.g., rhodochrosite, oligonite). Variable Mn contents were reported in sphalerite, from few up to thousands of ppm (Cook et al., 2009). Mn can enter the sphalerite and galena structure up to 7 mol.% and 3.5 mol.% MnS, respectively (Cook et al., 2009; George et al., 2015). Tellurium commonly occurs in assemblages with Bi or with Au. Bismuth tellurides are common mineral phases occurring in association with Bi-sulphosalts and Au mineralization in Pb-Zn skarn deposits (the present study; Cook and Ciobanu, 2004, Cook et al., 2007a,b,c), VHMS deposits (Vikentyev, 2006), Au deposits in sher zones (Bowell et al., 1990), Au orogenic deposits (Ciobanu et al., 2010) and Au quartz-vein systems (Cepedal et al., 2013), nickel mineralization in greenstone formation (Groves and Hall, 1978), neovolcanite formations with epithermal mineralization (Melnikov et al., 2009), and other hydrothermal vein systems (Melnikov et al., 2009; Pršek and Peterec, 2008; Plotinskaya et al., 2009). Tellurium mineralization, together with Bi, is commonly linked to Au occurrences (Ciobanu et al., 2009a; 2010). Cobalt and nickel minerals are not common in Pb-Zn deposits, however, they can enter stucture of some sulphide minerals. Cobalt may enter the sphalerite structure as a trace to minor element in some skarn deposits and may occur in concentrations over 1000 ppm 7.

(15) (Cook et al., 2009) and has positive correlation with Ni. Co and Ni were also reported as trace elements in pyrite, pyrrhotite, and arsenopyrite in different types of sulphide deposits (Brill, 1989; Thomas et al., 2011; Gregory et al., 2016; Gadd et al., 2016). Cadmium is one of the most important trace elements in the sphalerite structure, and occurs in relatively high concentrations. Typically, the Cd content in sphalerite has been reported in the thousands of ppm from various Pb-Zn deposits (Cook et al. 2009). Cadmium can be present also in the solid solution with galena, up to hundreds of ppm (Berthke and Barton 1971; Tauson et al., 2005; George et al., 2015). Cadmium very rarely forms its own mineral; the most common is greenockite (CdS), but its substitution for Zn in the sphalerite remains the main repository this element in sulphide minerals. Mercury occurs in primary Hg deposits in Au-As-Hg, Au-Sb-Hg, Au-Te-Hg, and AuCu-Hg minerals in ore-magmatic systems (Borisenko et al., 2006). According to Krupp (1988) significant quantities of mercury (e.g., > 0.1 ppm) can be transported in hydrothermal fluids, and Hg forms likely a HgS-ZnS solid solution with sphalerite. In many Pb-Zn deposits sphalerite may be dominant carrier, e.g. concentrations up to 16.35 wt.% Hg were reported from the Eskay Creek deposit (British Columbia, Canada) by Grammatikopoulos et al. (2006). Such sphalerite, are usually accompanied by other Hg-enriched minerals, like Hg-tetrahedrite. Radosavljević et al. (2006) reported Hg content between 0.30 and 6.47 wt% in sphalerite from the Podrinje Metallogenic District, Serbia. Low parts per million levels of Hg were reported in galena from various deposits by George et al. (2015), however this content may be due to inclusions of Hg-bearing phases that were not identified during the analyses. Gold is a common element in Pb-Zn systems, occurring either with high temperatureassemblages as native gold (commonly together with Bi), or in epithermal parts of the hydrothermal system, as native gold, or electrum, likely together with As, Hg and/or Sb. Gold is not incorporated into the sphalerite structure (Cook et al., 2009) or the galena structure, where George et al. (2015) reported parts per million levels of Au in galena, and suggested it is related to submicroscopic inclusions of Au minerals. Gold was reported as a common trace element in analyses of pyrite and arsenopyrite, in the range up to few or tens of ppm (e.g., Deol et al., 2012; Gregory et al., 2016). In a LA-ICPMS study of Bi-chalcogenides Cook et al. (2007) confirmed of presence Au as nano-inclusions Indium rarely forms own sulphide minerals, like indite (FeIn2S4), roquesite (CuInS2), or laforetite (AgInS2), nor does it typically occur as a native element. Indium is widely reported as a common trace element in sphalerite and can be incorporated in sphalerite via 8.

(16) a coupled substitution (Cu+In3+) ↔ (Zn2+, Fe2+), on the basis of solid solution between sphalerite and roquesite (e.g., Parasyuk et al., 2003). Sinclair et al. (2006) reported up to 6.9 wt. % of In in sphalerite from an In-bearing vein, replacement and breccia-hosted tin-base metal deposits in Mount Pleasant, New Brunswick, Canada, but the highest concetrations were proposed to be related to In-mineral inclusions. Indium is commonly linked to W or Sn mineralization, accompanying Pb-Zn ores (Qian et al., 1998). Seifert and Sandmann (2006) reported up to 0.38 wt. % of In in sphalerite from Zn–Sn–Cu stage of pollymetalic mineralization in Freiberg district, Erzgebirge, Germany. George at al. (2015) reported up to a few ppm of In in selected galena samples, and reported that these values do not vary significantly within that deposit. Thallium is present in the sphalerite structure in up to hundreds of ppm at the Red Dog deposit, Alasca, U.S. (Kelley et al., 2004), and is possibly incorporated in the Tl+0.5As3+0.5S. solid solution. (Xiong,. 2007).. Nriagu. (1998) documented thallium. concentrations up to 20 ppm in galena. Thallium can be incorporated in the galena structure through the following coupled substitution: Tl++Sb3+ ↔ 2Pb2+ (Balić-Zunić and Bente, 1995). There are also many Tl minerals, however, they are relatively rare. In the Balkan area, lorandite (TlAsS2), vrbaite (TlAs2SbS5), raguinite (TlFeS2), picopaulite (TlFe2S3), parapierrotite (Tl(Sb,As)5S8), rebulite (Tl5Sb5As8S22) were described from the Allchar hydrothermal-volcanogenic Sb-As-Tl deposit, Former Yuogoslav Republic of Macedonia (e.g., Janković and Jelenković 1994; Tomanec et al., 2015). Gallium occur only in few own minerals (e.g., gallite CuGaS2 and sohngeit Ga(OH)3), but is an important constituent of sulphides, and in particular in sphalerite. The highest concentrations of Ga are reported in sphalerite from low temperature Pb-Zn deposits (e.g., MVT-type). Melcher et al. (2006) reported Ga concentration in sphalerite above 3,000 ppm. In many occurrences the Ga content is increased when coupled with Ge. High concentrations of Ga in sulphide minerals are known from Kipushi (Zaire), Tsumeb (Namibia), and Ruby Creek (Alaska, U.S.), and the only Ga-Ge mine operated on oxide part of the Cu-Pb-Zn Apex deposit (Utah, U.S.), where Ga highest concentrations were in secondary jarosite (up to 0.7 %), and in some limonite (up to 2 %) (Bernstein, 1986). Germanium is known as a common trace element occurring in low-Fe sphalerite, and that mineral is thought to be the main source of this element (Höll et al., 2007). Germanium occurs, however, in some rare Ge minerals, like germanite (Cu26Fe4Ge4S32), rienierite ((Cu,Zn)11(Ge,As)2Fe4S16),. briartite. Cu2(Zn,Fe)GeS4,. polkovicite (Fe,Pb)3(Ge,Fe)1-xS4,. morozeviczite (Pb,Fe)3Ge1-xS4, and argutite (GeO2). Germanium was reported in the highest. 9.

(17) concentrations in sphalerite up to 3,000 ppm, stannite up to 2830 ppm, pyrite up to 20 ppm, enargite up to 500 ppm, and arsenopyrite up to 5 ppm (Bernstein, 1985). Cook et al. (2009) analyzed sphalerite from various deposit types, and the Ge concentrations were generally around a few ppm, with significant high concentrations (several hundreds of ppm) in low temperature Tres Marias Zn–Ge deposit, Mexico and in some of the Neogene Pb-Zn mineralization (Romania). According to Frenzel et al. (2014), Ge is supposed to be most abundant in low-temperature Pb-Zn deposits (e.g., MVT). In the Apex deposit (Utah, U.S.), Ge occurs in secondary goethite (up to 0.5 %), hematite (up to 0.7 %), and limonite (up to 0.5 %) (Bernstein 1986). Spaherite from Ge-rich mineralization at the Tsumeb deposit has relatively small Ge content, up to 68 ppm (Melcher, 2003). Cook et al. (2009) and Lin et al. (2011) considered Ge2+ for Zn2+ substitution, or involving Ge4+ with vacancies or defects to achieve charge neutrality. Belissont et al. (2014) suggested that Ge may be incorporated into Ag-rich sphalerite via 3Zn2+ ↔ Ge4+ + 2Ag+ based on analyses of samples from the vein-type Zn–Ge–Ag–(Pb–Cd) deposit of Noailhac – Saint-Salvy (Tarn, France). High-Ge chalcopyrite was described by Reiser et al. (2009) from the Barrigão remobilized vein deposit in the Iberian Pyrite Belt, Portugal, where this mineral contains between 0.1 to 0.4 wt. % of Ge. Höll et al. (2007) reported some other Cu-minerals, like enargite, bornite, tennantite–tetrahedrite, luzonite, sulvanite, and colusite, as significant Ge sources.. 10.

(18) 1.3. PB-ZN METASOMATIC-HYDROTHERMAL THE VARDAR ZONE. DEPOSITS IN THE. BALKAN. AREA AND IN. Pb-Zn mineralization in Kosovo, including the Stan Terg mine, and other Trepça deposits, is located in the central part of the Balkan region, in southeastern Europe. According to Heinrich and Neubauer (2002), this is a part of the Alpine-Balkan-Carpathian-Dinaride geodynamic province (ABCD). Ore deposits in Kosovo, Bosna and Herzegovina, Serbia, Macedonia,. Greece,. southern. Serbomacedonian–Rhodope. Bulgaria. Metallogenic. are belt,. related where. to. the. Oligocene-Miocene. polymetallic. Pb-Zn-Ag-Au. mineralization dominates, with several porphyry occurrences, like Maronia in the southern part of the region. Simillar polymetallic Pb-Zn deposits occur in Romania, eastern Serbia, and in northern Bulgaria occur and are part of the Late Cretaceus (Apuseni-Balkan) Banatite magmatic-metallogenic belt (e.g., Heinrich and Neubauer, 2002; Bonev et al., 2013, Melfos and Voudouris, 2016; Repstock et al., 2016). In the northern part of the ABCD province (Austria, northern Slovenia, Slovakia, eastern Ukraine, and northern Romania) numerous ore deposits in the Tertiary – Inner Carpathian Alpine metallogenic belt also occur (Heinrich and Neubauer, 2002). Besides Pb-Zn ores, also small porphyry, orogenic gold, or metamorphicorogenic mineralization occurrences are present (Figure 2) (Heinrich and Neubauer, 2002). The Serbomacedonian-Rhodope metallogenic belt is related to calk-akaline magmatism (Heinrich and Neubauer, 2002) and geologically it is connected with following tectonic units: Vardar Zone, Serbo-Macedonian Massif and Rhodope Massif. In the Kosovo area numerous occurrences of skarn, carbonate replacement and vein type of Pb-Zn mineralization are known, that are mostly related with so called Trepça Mineral Belt, or Kopaonic metallogenic district, and they are part of the Vardar Zone (Janković, 1995; Hyseni et al., 2010). The Pb-Zn mineralization in Kosovo is related to Oligo-Miocene subvolcanic intrusions of mostly quartz-latite composition and related to hydrothermal activity (Janković, 1995). The Vardar Zone is a kind-of suture zone, 40-70 km wide, going across the Balkan Peninsula, and is comprised of the oldest Paleozoic (ocean realm and “Veles Series” – island arc relics) and Mesozoic rocks, often metamorphosed, Jurassic ophiolites (serpentinite and peridotite with chromite occurrences), igneous rocks (of Cretaceous and younger age), and Oligocene-Miocene volcanic rocks (andesites, trachytes, dacites) and volcanosedimentary rocks (e.g., tuffs). The ore mineralization in the Vardar zone is mostly controlled by regional faults (Schumacher, 1954; Karamata et al., 1999). 11.

(19) F IGURE 2. S IMPLIFIED. GEOLOGIC / TECTONIC MAP DISPLAYING THE DISTRIBUTION OF MAJOR TECTONIC UNITS. AND ORE DEPOSITS IN THE. A LPINE –B ALKAN –C ARPATHIAN –D INARIDE (ABCD). REGION. (F ROM H EINRICH. AND. N EUBAUER , 2002).. The most significant Pb-Zn deposits related genetically to Oligocene-Miocene volcanic complexes in Kosovo are Stan Terg, Artana, Hajvalia, Kizhnice, Belo Brdo, Kopaonik, Crnac, and Drazhnje. The mineralization is hosted by volcanic rocks, mineralized shear-zones in serpentinites, schists, and replacement in carbonate sediments. The deposits in Kosovo hosts ores of different type including skarn, carbonate replacement, and vein mineralization. They are often interpreted as a magmatic-related system, however; porphyry mineralization has not been identified apart from small occurrences east of the Draznhje area (Janković, 1995; Hyseni et al., 2010). The most common ore minerals in the Vardar Zone are galena and sphalerite. In most of the deposits Pb dominates the ore system. Galena ore is commonly increased in Ag. In most of the occurrences the associated major minerals are pyrite and pyrrhotite, with less chalcopyrite, arsenopyrite and Sb-minerals. The predominant gangue minerals are carbonates (e.g., calcite, dolomite, siderite, rhodochrosite), quartz, and barite. In the occurrences where mineralization is hosted in limestones, near igneous contacts silicate (skarn) minerals are also. 12.

(20) common. The high temperature zones are abundant in pyrrhotite and contact-metasomatic silicates, whereas external zones are commonly increased in Sb-minerals (Schumacher, 1954). Many deposits in the Vardar Zone have been discovered and described during the late 20th century and as such most of the literature originates form that time. In recent years, detailed geochemical studies, and estimations of the physico-chemical condition of ore precipitation were done by Strmić Palinkaš et al. (2013; 2016), Kołodziejczyk et al. (2015) for the Stan Terg deposit (Kosovo); Šoštarić et al. (2011; 2013) for the Crnac deposit (Kosovo), and Radosavljević et al. (2012; 2016) for the Podrinje ore district (Serbia), Cvetković et al. (2016) and Stojanović et al. (2016) for the Rudnik deposit (Serbia). Similar mineralization in Romania was investigated in the recent years by Ciobanu et al (2000; 2006), Cook (1997), Cook and Ciobanu (2004), Wallier et al. (2006), Damian et al. (2008), and Buzatu et al. (2015). In the Rhodope area some of the most actual works include Marhev et al. (2005), Márton et al. (2010), Bonev et al. (2013), Melfos and Voudouris (2016), Repstock et al. (2016). Balkan deposits have been great importance during throughout civilization, starting during prehistoric times, where in the Majdanpek Cu mine stone-age tools were found. In ancient Roman times, mineral occurrences in the Balkan Peninsula were the main sources of Cu, Ag-rich galena, and Au (Schumacher, 1954). During medieval times, the mining activities in the Balkans were developed by Saxons, who went there from the Erzgebirge region, and most of the mines at that time operated in the area of present day Kosovo. Modern mining started after the First World War, and even today remains one of the most significant mining sites in Europe. The present day extraction of Pb-Zn ores in the central Balkans is done by several mining companies. The main Pb-Zn producer in Kosovo is the Trepça Mining Company, who owns mining licenses for Stan Terg, Artana, Belo Brdo, and Crnac deposits. Kosovo Metals Group Company recently started ore extraction in the Drazhnje deposit. Mineco Ltd., operates the Gross mine (Srebrenica orefield) in Bosnia and Herzegowina, as well as the Rudnik and Veliki Majdan mines in Serbia. In Macedonia the production of Pb and Zn is dominated by Indo Minerals and Metals DOOEL, that operates the Zletevo and Toranica mines, and the Solway Investment Group Ltd., operates the Buchim Mine. In southern Bulgaria 39 Pb-Zn deposits were found in the Madan orefield and the mineralization was extracted by the GORUBSO mining company; after the privatization process was completed many of mines are still active and Madan area remains most important Pb-Zn mining district in Bulgaria. The numerous deposits in Romania are mostly of historical significance. Presently, numerous 13.

(21) companies are working throughout Balkans on re-opening of old Pb-Zn mines, as well as in greenfield and brownfield exploration projects in the vicinity. The Stan Terg deposit in Kosovo is the largest deposit (29Mt with ore grade 3.45% of Pb and 2.30% of Zn and 80 g/tonne of Ag) in one of the most important historical mining districts in Europe for lead, zinc and silver (Forgan 1948; Hyseni et al., 2010). In the literature, this deposit is also known under other names, including Stari Trg, Stan Trg, or Trepča. Trepça is the name of the mining company that owns several ore deposits in the area including the skarn type Pb-Zn Stan Terg deposit. From 1931 to 1998 Trepça co-produced 4,115 tonnes of Bi and other associated metals such as Sb, Cd, Au and Ag. Traces of Ge, Ga, In, Se and Te during ore processing were also reported (Féraud and Deschamps, 2009). The significance of the Trepça ore belt has been confirmed by many authors who have described different types of Pb-Zn mineralization such as skarn, hydrothermal replacement, and vein mineralization that are thought to be controlled primarily by faults (e.g., Schumacher, 1954; Janković, 1995; Karamata et al., 1999; Hyseni et al., 2010). The mines of this whole area now are rather small compared to huge complex that during the 1980s employed 20,000 workers. The total reserves of the district reached 60.5 million tonnes of ore grading 4.96% Pb, 3.3% Zn and 74.4 g/t Ag, thus resulting three million tones of Pb, two million tonnes of Zn and 4,500 tonnes of Ag (Feraud and Déschamps, 2009). The average Bi grades in the Stan Terg ore vary between 90 and 100 g/t (Forgan, 1948; Schumacher, 1950).. 14.

(22) 1.4. GEOLOGICAL SETTING OF THE STAN TERG DEPOSIT The Stan Terg deposit is located in the central part of the Vardar Zone, in the Trepça. mineral belt, in the territory of Kosovo (Figure 3). Deposits and occurrences in this ore district are considered to be related to the Kopaonik granodiorite massif, or related magmatic stocks that are not exposed on the surface. Stan Terg is the largest, world-class, Pb-Zn deposit in Kosovo, located in the central part of the Trepça belt within a chlorite facies metamorphosed terrane (Figure 3). The Vardar Zone crossing through the Kosovo territory contains fragments of Triassic sediments, phyllites, volcanoclastic rocks, and Upper Triassic carbonates. Ultrabasic rocks and serpentinites are of Jurassic age and are part of an ophiolite mélange sequence. Cretaceous rocks are represented by a complex series of clastics, serpentinites, volcanics and volcanoclastic rocks of basaltic composition and carbonates. In numerous places, Tertiary (Oligocene-Miocene) lavas, sub-volcanic intrusives, and pyroclastic rocks of andesite, trachyte, and latite composition occur. In the Trepça Mineral Belt dominate NNW-SSE tectonic structure, and according to them three mineralization zones have been identified: Drazhnje-Artana Zone; Belo Brdo-Stan TergHajvalja Zone; and the Crnac Zone (Hyseni et al., 2010).. F IGURE 3. S IMPLIFIED OCCURRENCES OF. GEOLOGICAL MAP OF THE. P B -Z N. T REPÇA M INERAL B ELT. MINERALIZATION ( MODIFIED AFTER. H YSENI. WITH MARKED MINES AND. ET AL .,. 2010).. 15.

(23) The Stan Terg deposit is located at the central part of Zone II in the Trepça belt within a chlorite facies metamorphosed terrane. Metamorphism is possibly related to the thrusting of the ophiolite complex over Triassic limestones and is suggested to have an isochemical character (Strmić Palinkaš et al., 2013). According to Maliqi (2001), the ore mineralization at the Stan Terg deposit is hosted in a metamorphosed sedimentary complex of middle Triassic age (Figure 4). The host rock is mainly a limestone (marble?) layer located in between a thicker schist complex. In the vicinity there are little Jurassic ophiolite outcrops, and the most exposed rocks on the surface are Triassic volcanics and pyroclastic rocks. In the older literature (until 1973) the host rocks were dated to be Silurian-Ordovician, however the presence of conodonts helped to estimate the age to be Triassic (Féraud et al., 2007).. F IGURE 4. G EOLOGICAL. MAP OF THE STAN TERG AREA ( MODIFIED AFTER. H YSENI. ET AL .,. 2010).. 16.

(24) The ore mineralization at Stan Terg is spatially and temporally linked to the post-collisional magmatism of Oligocene- (23-26 Ma; according to Strmić Palinkaš et al., 2013) or of Miocene age (16-17 Ma; according to Féraud and Deschamps, 2009). The magmatic rocks in the vicinity are exposed on the surface in the Kopaonik Mountains in the north of Kosovo. They are mainly of calc-alkaline and in some localities high-K calc-alkaline affinity, represented by granodiorite and dacite-andesite intrusions. They were formed in a post-collisional environment, during partial melting of a previously metasomatized continental lithosphere. The area is widely covered by felsic pyroclastic sediments (Féraud and Deschamps, 2009). The main tectonic structure in middle Triassic sediments is an anticline plunging at about 40° NW, with a prominent phreatomagmatic breccia pipe along the hinge of the asymetric anticline. Triassic carbonates (mainly marbles) build the core of the anticline. They are surrounded by sericite schists. The breccia pipe is composed of country rocks, trachyte and quartz-latitic rocks (Figure 5). The ore was extracted from XI mining horizons. Presently the most ore is excavated from IXth and Xth horizons. The old open pit has 830 m asl, whereas XIth horizon is at 15 m asl. The deposit has been recognized several tenths meters downwards (to the possible XVth horizon) and continuation of ore was confirmed, however the final depth has not been indicated.. F IGURE 5. C ROSS. SECTION OF THE. S TAN T ERG. DEPOSIT ( MODIFIED FROM. T REPÇA. INTERNAL DOCUM ENTS ).. 17.

(25) The diameter of the breccia pipe is about 100-200 m and the orebodies stretch parallel to the conduit as columns. The orebodies at the Stan Terg deposit are generally hosted in the Mesozoic carbonates at the contact with an andesitic rock and breccia forming a pipe, as well as in the schists and the volcanic rocks in the distal to the central pipe (Hyseni et al., 2010). Eleven main manto-like orebodies were identified. In several parts of the deposit skarns were formed at the interfaces between limestone and the breccia pipe (Strmić Palinkaš et al., 2007; Hyseni et al., 2010). There is no visible contact between the ore mineralization and the magmatic rocks, and therefore the deposits likely resulted from the interaction between the carbonates and the hydrothermal mineralizing fluids. Féraud et al. (2007) considered that the source of metals was derived from earlier formed massive sulphide deposits within an ophiolite belt, and later remobilization of metals took place during subsequent subduction. According to Strmić Palinkaš et al. (2013; 2016) the source of the fluids is magmatic, and was probably derived not only from the volcanic magma, but also possibly from a magma chamber below the deposit. The hydrothermal fluids have been also mixed during infiltration through the country rocks. Vydrin (1958) distinguished nine different types of orebodies depending on their structure and morphology, and tectonic setting. He studied fissures and ruptures, and their relationship to the ore. Parts of the orebodies are related to skarn mineralization, parts have mantos shape, and significant ore precipitated as a karst fillings. Karst fillings originated by the corrosive action of the metalliferous hydrothermal solutions dissolving the limestone (Forgan, 1948; Schumacher, 1950; Féraud et al., 2007). It is also likely that the previous fissures and ruptures that occurred during the prior folding period were extended. The tectonic and structural gaps were developed likely during ore deposition, since presently some of the voids or fissures are free of ore, eventually filled partially only by later recrystalized calcite.. 18.

(26) 1.5. PREVIOUSLY. MINERALOGICAL AND GEOCHEMICAL STUDY ON THE. STAN TERG. DEPOSIT. The ore mineralization at the Stan Terg deposit is dominated by Pb and Zn, with less Ag and Bi (e.g., 29 Mt of ore at 3.45% Pb, 2.30% Zn, and 80 g/t Ag). The main ore minerals are sphalerite and galena, accompanied by Fe-sulphides (pyrite, pyrrhotite). The skarns at Stan Terg are calcic and consist of typical contact-metamorphic assemblages, with garnet, hedenbergite, ilvaite and actinolite. Dangić (1993) also listed in this assemblage magnetite, pyrite, pyrrhotite, chalcopyrite, sphalerite and galena. Strmić Palinkaš et al. (2013) described a prograde magmatic stage with pyroxene and garnet, and a retrograde skarn and hydrothermal stage with ilvaite, magnetite, arsenopyrite, pyrrhotite, marcasite, pyrite, quartz and carbonates. The main ore deposition event was during the hydrothermal stage. The carbonatereplacement hydrothermal ores at Stan Terg deposit comprise the most economically significant ore minerals; mainly dominated by several generations of pyrite, galena, sphalerite, chalcopyrite, arsenopyrite, marcasite and lead-antimony sulfosalts (Féraud and Deshamps, 2009). The gangue minerals are various Ca-Mn-Fe-Mg carbonates (e.g., calcite, dolomite, siderite, rhodochrosite, and numerous intermediate members) and quartz (Dangić, 1993). Recently, Kołodziejczyk (2012) proposed new precipitation stages, according to mineralogical research, that indicated presence of skarn and hydrothermal stages. The hydrothermal stage was divided into four sub-stages: “Pb+Zn”, “Cu”, “Ag” and “Sb”, followed by weakly developed secondary mineral paragenesis. Galena and sphalerite were mostly precipitated during the first stage. The “Cu” stage consists of chalcopyrite, bournonite, tetrahedrite and stannite. The “Ag” stage is represented by deposition of silver-bearing galena with inclusions of silver sulfosalts (polybasite, pyrostilpnite, pyrargyrite, stephanite, freieslebenite), Ag-rich tetrahedrite, freibergite and Pb-Sb sulfosalts (Pršek et al., 2012). The last “Sb” stage contains boulangerite and heteromorphite. Hydrothermal mineralization also occurs as small veins and veinlets, which run offset from the main orebodies. They consist mainly of pyrite, sphalerite and galena, and are more common in the distal orebodies at the northern part of the deposit. In several places in the mine, breccia-type mineralization occurs, either within the phreatomagmatic volcanic pipe, or within limestones in the distal parts of the deposit, where brecciated wallrock fragments are 19.

(27) cemented by sulfides and vice versa. Vydrin (1958) has identified two genetic types of breccia, and three species of breccias formed at a different time: 1# eruptive pre-ore breccia; 2# tectonical inner-ore breccia; and 3# tectonical post-ore breccia. The variety of the ore styles observed, as well as numerous other smaller occurrences in the vicinity, and epithermal cinnabar stringers within the overlying tuffs, indicate the presence of an extended magmatic-hydrothermal ore system in Stan Terg. Previous geochemical works by Këpuska and Fejza (2000), Këpuska et al. (2001), Durmishaj et al. (2006), Féraud and Deschamps (2009), Hyseni et al. (2011), Šoštarić et al. (2011; 2013) and Palinkaš et al. (2013) have demonstrated the chemical composition of the orebodies and the ore minerals of the Stan Terg ore prospect as well as of some adjacent ore mineralizations (e.g., Crnac, Badovc, Ajvalia, Kizhnica deposits). According to these studies Pb in the Kosovo deposits reaches up to 6 %, Zn up to 5% and Ag up to 75 g/t, although a large dispersion of the grades from one orebody to the other has been reported. Këpuska (1998), Këpuska and Fejza (2000) and Këpuska et al. (2001) reported results concerning distribution of main elements and trace elements in the main ore forming minerals in the deposit. In these studies the presence of W, Ga, Ge, In, Se, Tl, In in sphalerite, galena, pyrrhotite and pyrite was described The results show an average content of Cd in sphalerite 2640 ppm and in galena 51 ppm and an average content of In in sphalerite and galena 97 ppm and 55 ppm respectively. The average content of Bi in galena is 342 ppm. In addition, small amounts of Ga in sphalerite (av. 10 ppm), Ge in pyrite (max. 180 ppm), in dolomite (1 ppm), in rhodochrosite (3 ppm) and in the skarn minerals (2 ppm), Tl in galena (av. 32 ppm), Se in sphalerite (max. 250 ppm) and Hg in sphalerite (av. 22 ppm) have been also measured. Këpuska et al. (2001) described in more details the In content in the ore. They noticed that indium is related to high temperature sphalerite and its content increase with depth. The content of In in sphalerite varies between 10 and 600 ppm, in galena it is approximately 55 ppm, in pyrite 7 ppm and in pyrrhotite 5 ppm. Féraud and Deschamp (2009) showed that the Bi content in run-of-mine ore is about 100 ppm and is incorporated in galena in the form of native Bi, cosalite and bismuthinite as small inclusions. The Cd content is 200 ppm in the ore and Au is found content in ore and in the final concentrate, in a range about 0.2 ppm. The concentration of W and Sn is 104 ppm and 36 ppm respectively, being incorporated in the minerals scheelite and stannite, respectively. Traces of Ga, Ge, In, Se, Te and Tl were reported from ore bulk samples, as well as Zn and Pb concentrates. 20.

(28) A conclusion that can be drawn from the published data so far is that Ag and Bi are related to galena, and Cd, In, Hg, Ge and Ga are primarily found with sphalerite. Gold, Ag, Bi, Te, Se, Tl are common in galena and sphalerite as well (Féraud and Deschamp 2009). Finally Strmić Palinkaš et al. (2013; 2016) presented data from her Ph.D. project on the Stan Terg deposit. This included EPMA data for trace elements in sphalerite, galena, pyrite, pyrrhotite, arsenopyrite and chalcopyrite. She also estimated the conditions of ore formation. She classified the deposit as a distal Pb-Zn-Ag skarn. The prograde stage, abundant in pyroxenes (Hd54−100Jo0−45Di0−45), occurred in a low oxygen fugacity (<10−31 bar) and anhydrous environment, in a temperatures range between 390° and 475°C, with a pressure below 0.09 GPa. The isotopic composition of fluid inclusions in hedenbergite, δD = −108 to −130‰; δ18O = 7.5−8.0‰, indicate that magmatic fluids were modified during its infiltration into the country rock. The retrograde stage was estimated between 350° and 380°C (arsenopyrite geothermometer) with a S fugacity between 10−8.8 and 10−7.2 bars. The primary sulphides precipitated from moderately saline Ca-Na chloride fluid at around 350°C. Fluid inclusions in sphalerite (δD = −55 to −74‰; δ18O = −9.6 to −13.6‰), indicate its dominantly meteoric origin. Sulfur isotopes in sulphides indicate magmatic origin of sulfur (δ34S is between −5.5 and +10‰). The recent mineralogical studies (Kołodziejczyk, 2012; Kołodziejczyk et al., 2012a,b; Pršek et al., 2012) identified eight additional ore minerals (freibergite, stephanite, pyrostilpnite, freieslebenite, polybasite, heteromorphite, mackinavite, copiapite) in the ore mineral paragenesis and suggested an obvious zoning with a horizontal dispersion of Bi and Ag. Preliminary results were presented in numerous conference abstracts, including two SGA congresses (Kołodziejczyk et al., 2013; Kołodziejczyk et al., 2015). Further geochemical and mineralogical results included in this thesis have been published in Kołodziejczyk et al. (2015), Kołodziejczyk et al. (2016a), Kołodziejczyk et al. (2016b). Those studies comprise mineralogical data of Bi-bearing sulphosalts not previously described at Stan Terg, Ag-mineralization and Sn-mineralization. Two further papers concerning mineralogy of Bi-tellurides, and trace element content in the main sulphides by LA-ICPMS are expected to be submitted for publication soon.. 21.

(29) 1.6. OBJECTIVE OF THE STUDY AND PROBLEM STATEMENT Europe has many ore deposits of economic grade, and their successful exploration faces. stiff competition for different types of land uses, and occurring in a highly protected environment, as well as several limitations (e.g., price of commodities, geographic setting) in extraction of these deposits. The Trepça ore belt in Kosovo is one of the most significant metallogenic provinces of Europe, hosting a large number of ore deposits that may provide essential mineral wealth to the people of Kosovo. Those deposits are considered highly prospective with great potential to additional reserves and resources, not only for Pb, Zn and Ag, but also for Cu and Au, and including various critical metals. The “critical” (i.e., strategic) raw materials, particularly the high technology metals (e.g., Ga, Ge, In), are very important for sustainable industrial economies, and European industry is highly dependent on imports of strategically important metals from third world countries. The existing literature data, as well as preliminary observations in this Ph.D. investigation indicate that the content of ore minerals as well as minor elements in the Stan Terg mine is variable on different mining levels in the individual orebodies. The intense modern mining operations of the past, since early 1930’s, resulted in the construction of approximately 12 km of underground workings at the Stan Terg mine. However, many more ancient and medieval corridors and shafts are located throughout the 100 km2 mining district. Most of these mining galleries are still preserved today and are accessible. The main shaft of the Stan Terg mine reaches the depth of 925 m below the surface (Hyseni et al., 2010). In many cases, the ore is very well exposed in the underground workings showing the textures and structures of the various mineralization styles (Kołodziejczyk et al., 2012). Consequently, the accessibility of Stan Terg ore mineralization in the throughout the deposit is an excellent opportunity for an extensive and detailed geochemical investigation for trace metals including strategic metals. New geochemical interpretations of the Stan Terg ore deposit can provide an opportunity to investigate the spatial distribution and the mineral chemistry of strategic metals along with their association with the sulfides, the magmatism and the various mineralization styles. Through this approach we may obtain information for developing a model for the formation process of the critical and precious metals (e.g., Au, Ag) in a magmatic-hydrothermal system. A small number of published and unpublished results of the ore and host-rocks chemical composition and the ore mineral chemistry, demonstrate some remarkable findings, for which 22.

(30) questions arise requiring a focused investigation for getting the proper answers; e.g. silver is not homogeneously distributed in the Stan Terg polymetallic ore system which possibly implies that there are factors that limit its distal or proximal distribution from the volcanic host rocks. Or, it is still uncertain whether In, Ge and Ga are concentrated in the Zn-rich ore and in which form do those elements occur. The goal of the Ph.D. thesis project is to determine the distribution, and concentration, of high technology metals (e.g., In, Ga, Ge, Sn, Bi, Te, Cd) and their relationship to the precious metals (e.g., Ag, Au) within the various ore styles in the Stan Terg mineralization, that can be studied as a model ore district for exporting valuable data and knowledge for the high technology metals prospection and help therefore in the near-future exploitation in Kosovo, or in the other similar mineral districts around the world. Among the investigated metals, In, Ga and Ge belong to the list of “critical raw materials” established by the European Union. Silver, Au, Bi, Te and Cd commonly co-exist with lead-zinc ores and are also of great technological importance.. 23.

(31) 2. METHODS Integrated field work, mineralogical, and geochemical studies were done to describe the mineralogical and geochemical diversity in the Stan Terg deposit. The setting of the orebodies was studied in the mine during numerous visits underground. During six years of cooperation with Trepça geologists a representative set of samples was collected. The detailed mineralogical study was done by mean of reflected light microscopy, scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). These investigations were further complemented by trace elements analyses of selected ore minerals using laser-ablation inductively coupled mass spectrometry (LA-ICPMS).. 2.1. SAMPLING STRATEGY. The ore from the Stan Terg deposit is extracted presently from different horizons and different orebodies. All samples were collected underground from all accessible places from 2011-2015. The samples investigated comprise different kinds of ore, with different crystalsizes from various mineral associations and parageneses. From all of the orebodies visited, representative kinds of ore have been selected. The samples. investigated. comprises. skarn-related. mineralization,. typical. hydrothermal. assemblages, ore form veins of different sizes, as well as brecciated samples of ore. Polished sections of ore and 25 mm diameter polished epoxy grain mounts were prepared. in. the. polishing. laboratory at. the. Faculty of. Geology,. Geophysics,. and Environmental Protection, AGH-UST, Krakow, and at the polishing laboratory at the Comenius University in Bratislava, Slovakia. Grain mounts were prepared for the purpose of in situ geochemical trace elements analyses on selected sulphide crystals (picked to be free of inclusions). In the Trepça mine nomenclature the number of orebodies refer to the mining horizon, e.g., numbers in the 140 series (like 147-C, 140, 141, 149, 149-C3, etc.) indicate that that the sample originates from the stopes in the Xth horizon, whereas numbers 130s refer to IXth horizon, and numbers 120s refer to VIIIth horizon, etc. If one orebody is divided into several thinner and separate parts the numbers are overwritten with letters of an alphabet (e.g., 147-B0, 147-C). 24.

(32) The numbers of samples collected and polished sections used in this research project refer to the number of the orebody they came from, e.g., sample No. 140-1, is the number of 1st sample collected in the orebody No. 140, that is in the Xth horizon. A list of polished sections investigated with brief mineralogical descriptions is in Appendix 1, together with the mine map from the Xth horizon and numbers of orebodies.. 2.2. MINERAL IDENTIFICATION: MICROSCOPIC OBSERVATIONS. Research based on microscopic observations in reflected light was done in the Microscopy Laboratory at the Department of Economic Geology at the Faculty of Geology, Geophysics and Environmental Protection, AGH-UST, Kraków. A Nikon Optiphot polarizing reflected/transmitted light microscope was used. Photomicroscopy was done using a Sony Exwave HAD digital camera interfaced to the Nikon Optiphot polarizing microscope, and was used to find selected regions for the EPMA and LA-ICPMS analyses. This documentation provides the information about the distribution, shapes and sizes of the minerals investigated. Additionally back-scattered electrons images (BSE) were acquired using the JEOL JXA-8230 Super Probe electron probe microanalyzer (EPMA). Those BSE images were used to reveal mineral zoning, and to distinguish boundaries of mineral phases intergrown in aggregates of uniform optical properties under high magnification.. 2.3. GEOCHEMICAL ANALYSES: EPMA AND LA-ICPMS. 2.3.1 ELECTRON PROBE MICROANALYZER (EPMA) The chemical composition of minerals in this study were determined using a JEOL JXA-8230 Super Probe EPMA with five WDS detectors and an EDS system in the AGH-KGHM Critical Elements Laboratory at the Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology in Kraków, Poland. Quantitative mineral chemistry was determined with wavelength dispersive spectroscopy (WDS) techniques, using standard ZAF techniques with the JEOL software.. 25.