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Trepca - Stan Terg / Stari Trg

Kosovo

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The Trepča Pb-Zn-Ag deposit and Stan Terg/Stari Trg mine is located near the town of Kosovska Mitrovica, about 40 km NW from Priština, Kosovo (#Location: 42° 56' 19"N, 20° 54' 59"E).

Trepča is hosted within the Kopaonik block of the western Vardar zone in the easternmost part of the Dinarides. The Vardar zone contains numerous economically significant Pb-Zn-Ag, Sb and Mo deposits, as well as smaller Cu, Fe, Sn, W and Au deposits. The 80 km long Trepča Mineral Belt within Kosovo, comprises a string of Pb-Zn-Ag deposits, extend northward from Kosovo and southern Serbia, and through western Serbia (Kiževak, Sastavci, Rudnik and Veliki Majdan) to Srebrenica in easternmost Bosnia. The deposits of the belt include skarn, hydrothermal replacement, and vein type Pb-Zn-Ag deposits (Janković, 1995). The most significant deposits in the belt include Stari Trg/Stan Terg at Trepča, Crnac, Belo Brdo, Kišnica, Avajlija and Novo Brdo, with a total combined historical production of ~60.5 Mt @ 8% Pb+Zn and >4500 t of Ag. They are related to Tertiary post-collisional magmatism in the western Vardar zone (Cvetković et al., 2004; Borojevivić Šoštarić et al., 2011).

Mining in the Trepča area dates back to pre-Roman times and persisted through the Middle Ages. The Roman and Ottoman Empires fought to take control of the silver mines in Kosovo and at a later stage the Serbian Middle Kingdom produced much of its coinage from silver mined at Artana/Novo Berdo. Modern production started with the formation of Trepča Mines Limited in 1927. Subsequently, lead-zinc mining commenced in 1930 at the Stan Terg. Production continued through the Second World War, and then under state ownership until 1999. Between 2000 and 2008 the mine was administered by the United Nations Mission in Kosovo, and in 2008 passed into the administration of the Privatisation Agency of Kosovo.

Reserves in 2012 were 29 Mt @ 3.45% Pb, 2.30% Zn, 80 g/t Ag (ITT/UNMIK 2001 report). Past production was 34 Mt of ore (Palinkaš et al., 2013).

The Vardar Zone occupies the central core of the Balkan Peninsula, from Greece in the south, then NNW through Macedonia and Kosovo into Serbia. It is bounded by the Mesozoic and younger Dinarides and the Hellenides to the west, and the Serbo-Kosovaro-Macedonian Massif in the east which has a late Proterozoic metamorphic basement, and is interpreted as a main suture zone between the Adriatic and the Euroasian plate. It preserves tectonic units of both oceanic and continental origin (Dimitrijević, 1997, 2001; Karamata et al., 2000; Zelić et al., 2010). The the Vardar zone has been subdivided into three subzones (Dimitrijević 1995), the:
• External Vardar subzone in the west comprising the Srem, the Jadar, and the Kopaonik blocks;
• Central Vardar subzone; and
• Internal Vardar subzone in the east.
The Kopaonik block of the External Vardar subzone is composed of metamorphosed Palaeozoic and Triassic rocks overlain by a composite ophiolite/mélange complex. The ophiolitic mélange has a sandy to silty-clay matrix enclosing a mixture of clasts and olistoliths of limestone, chert, sandstone and well-developed turbidite, as well as magmatic rocks that include dolerite, gabbro and ultramafic rocks. A weakly metamorphosed mélange of Jurassic age with predominantly basaltic clasts, is developed over the eastern margin of Kopaonik Block. In contrast, the western margin of the Block is overlain by a Jurassic-Cretaceous mélange characterised by a predominance of sandstones over other sedimentary and magmatic rocks (Sudar and Kovacs, 2006, and references cited therein). The Kopaonik block was the site of considerable volcanic activity during the Oligocene-Miocene, characterised by numerous lava flows and extensive masses of volcaniclastic rocks, mainly trachytes (with K/Ar and Ar/Ar ages of 23 to 26 Ma; Strmić Palinkaš, 2009), quartz-latites, andesites and pyroclastic accumulations (Janković, 1995). The volcanic activity was contemporaneous with the deposition of lacustrine sedimentary rocks (e.g., Marović et al., 1999).

The principal host to mineralisation at Trepča is recrystallised Upper Triassic limestone with a well developed karst system. Calcite grains vary in size from several millimetres at locations distal to mineralisation, to as much as several cm at the contact with orebodies. The host Triassic limestone occurs within the core of an anticline plunging at ~40° NW, that is capped by sericite schist. A phreatomagmatic breccia pipe is developed in the hinge of the asymmetric anticline, at the contact between the limestone and overlying schist (Schumacher, 1950, 1954; Féraud et al., 2007; Strmić Palinkaš et al., 2007; Strmić Palinkaš, 2009). This pipe has a hydrothermally altered trachyte core (with K/Ar and Ar/Ar ages of 24 to 23 Ma; Strmić Palinkaš, 2009), enveloped by a breccia mantle. The breccia does not host ore mineralisation, but has been interpreted as a principal trigger for ore deposition (Palinkas et al., 2013).

The breccia pipe has characteristics consistent with a phreatomagmatic generated maar-diatreme breccia (Féraud et al., 2007; Strmić Palinkaš et al., 2007; Strmić Palinkaš, 2009). These include an inverted cone shape with a vertical extent of up to 800 m and as much as 150 m in diameter. The upper part of the breccia pipe is characterised by the presence of a hydrothermally altered trachyte dyke located within its core, which despite the intensity of alteration, retains a porphyritic texture. The white fine-grained alteration matrix is composed of muscovite, quartz and K feldspars. Sanidine phenocrysts are partially altered to muscovite, quartz-muscovite and quartz. The altered dyke is surrounded by a polymict breccia mantle of angular to well-rounded clasts ranging from a few centimeters to several metres that occupy up to 90 vol.% of the breccia. The principal clast types are country rock limestone and schist, together with magnetite- and sulphide-bearing fragments, as well as juvenile trachyte fragments. Recrystallised limestone clasts usually have a fresh white crystalline core and a brownish reaction rim of fine-grained Mn-enriched siderite and pyrite. Rarely, limestone clasts are intensely replaced by siderite enriched in Ca and Mn and impregnated by pyrite associated with microcrystalline quartz. Monomineral dickite aggregates and euhedral quartz occupy cavities (Strmić Palinkaš et al., 2009). There are a variety of magnetite- and sulphide-bearing clasts:
• Fibro-radial arsenopyrite aggregates accompanied by magnetite, embedded in recrystallised limestone fragments. Arsenopyrite postdates magnetite.
• Clasts with a magnetite core and pyrite rim, commonly found on the outer rim of the breccia pipe. Magnetite forms fibro-radial to spherulitic aggregates, whilst small masses of pyrite occur between magnetite grains. Pyrite is usually fractured, crushed and accompanied by andradite garnets, while the outer rim of clasts are characterised by the predominance of fresh pyrite accompanied by carbonates and quartz.
• Pyrite-pyrrhotite clasts are predominantly composed fractured pyrite and pyrrhotite. The interstices between grains is filled with fine-grained carbonates and quartz. The breccia matrix comprises fine-grained rock flour. The contact between the breccia and the wall rocks is sharp but locally cut by lateral fractures filled with milled matrix fluidised breccia or with angular jigsaw-puzzle breccia (Palinkaš et al., 2013).

Travertine deposits, composed of Ca-Fe carbonates (calcite, ankerite, siderite) significantly enriched in Mn, are found locally as an upper layer capping the deposit, marking a preserved palaeosurface. Fine-grained galena scattered within the carbonate matrix of the travertine suggest its deposition was associated with the ore-forming processes (Strmić Palinkaš, 2009).

Whilst low-grade mineralisation is found along elongated paleo-karst features and cavities, commonly associated with skarn alteration, economic massive sulphide ore occurs as continuous, columnar shaped carbonate replacement ore bodies. The later are located along the carbonate-schist contact and dip parallel to the plunge of the anticline and to the structural fabric and the dip of the flanks of the structure. The ore bodies on this contact are distributed over a strike length of ~1200 m, and have been tested to a depth of 925 m below the surface. They appear to range from <1 to several tens of metres, to as much as 70 m, in thickness. The larger ore bodies occur in the footwall contact of the volcanic breccia pipe and are composed of massive Pb-Zn sulphides, with associated ilvaite and hedenbergite garnet as well as magnetite, pyrite and chalcopyrite associated with skarn alteration, together with Fe-rhodochrosite, siderite, ankerite and dolomite. This skarn-type mineralisation also accompanies the smaller ore bodies and sub-economic pockets associated paleo-karst cavities (Hyseni, et al., 2010).

The principal skarn assemblage at Trepča comprises Ca-Fe-Mn silicates, including pyroxenes, ilvaite and minor garnets, with a Ca-Fe-Mn ±Mg carbonates and quartz. Paragenetic studies show that the skarn assemblage was formed in several stages. The prograde stage has an anhydrous character with the major mineral being hedenbergitic pyroxenes, occurring as prismatic crystals that are 0.5 to several cms long, usually forming fibro-radial to spherulitic aggregates. Ca-Fe garnets (andradite) are present but rare, exclusively found in the uppermost levels of the deposit. The retrograde stage has a predominantly hydrous nature with significant ilvaite, occurring as black prismatic crystals up to 10 cm long, with a vitreous lustre. Carbonates, quartz and pyrite form distinct zones within this stage (Palinkaš et al., 2013).

Hydrothermal ore minerals commonly overprint the pyroxene-rich calcic skarn, although skarn alteration occurs free of the ore assemblage, while ore mineralisation without a skarn precursor, is also found. The ore assemblage comprises both oxide and sulphide minerals. Magnetite mostly occurs in the form of pseudomorphs after hedenbergite. Pyrrhotite clusters sporadically replace pyroxenes, and locally pyroxenes are completely converted into pyrrhotite and/or pyrite. The primary fibro-radial texture is preserved, and sulphides are accompanied by a mixture of carbonates and quartz (Palinkaš et al., 2013).

The most abundant sulphide minerals are black sphalerite, galena, pyrite and pyrrhotite. Pyrite is the earliest deposited, relative to galena and sphalerite, although minor pyrite continued to precipitate throughout the whole interval of sulphide deposition. Galena precedes sphalerite, whilst chalcopyrite locally replaced pyrite and occurs as very fine inclusions in sphalerite. Marcasite, arsenopyrite, pyrrhotite and colloform pyrite have only been found in the ore assemblages with a skarn precursor. In detail, the ore mineralogy is very varied and includes a number of primary, as well as secondary Pb-Zn sulphides in cavities and vugs, including rare minerals such as boulangerite (Palinkaš et al., 2013; Hyseni, et al., 2010).

The most recent source geological information used to prepare this summary was dated: 2013.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Hyseni, S., Durmishaj, B., Fetahaj, B., Shala, F., Berisha, A. and Large, D.,  2010 - Trepca Ore Belt and Stan Terg mine - Geological overview and interpretation, Kosovo (SE Europe): in    Geologija   v.53, pp. 87-92.
Lehmann, S., Barcikowski, J., von Quadt, A., Gallhofer, D., Peytcheva, I., Heinrich, C.A. and Serafimovski, T.,  2013 - Geochronology, geochemistry and isotope tracing of the Oligocene magmatism of the Buchim-Damjan-Borov Dol ore district: Implications for timing, duration and source of the magmatism: in    Lithos   v.180-181, pp. 216-233.
Palinkas, L.A., Sostaric, S.B. and Palinkas, S.S.,  2008 - Metallogeny of the Northwestern and Central Dinarides and Southern Tisia: in    Ore Geology Reviews   v.34, pp. 501-520.
Palinkas, S.S, Palinkas, L.A., Renac, C., Spangenberg, J.E., Luders, V., Molnar, F. and Maliqi, G.,  2013 - Metallogenic Model of the Trepca Pb-Zn-Ag Skarn Deposit, Kosovo: Evidence from Fluid Inclusions, Rare Earth Elements, and Stable Isotope Data: in    Econ. Geol.   v.108, pp. 135-162.


Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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