Ivan Jurković

Geochemical characteristics of mercurian tetrahedrite, barite and fluorite from the Duboki Vagan, Glumac and Dubrave-Dugi Dol barite deposits, south of Kreševo, Mid-Bosnian Schist Mts.

The geochemical characteristics of tetrahedrite and barite of the Duboki Vagan barite deposit near the town of Kresevo in the MBSM (Mid-Bosnian Schist Mountains) have been determinated and correlated with the results of previously studied barite, from the adjacent Glumac deposit, and fl uorite, from the Dubrave-Dugi Dol barite deposits. The studied tetrahedrite is characterized by a high content of Au (39 ppm) and Ag (>300 ppm), the presence of Co (63.5 ppm), Ni (266.2 ppm) and Cd (313,6 ppm) in the crystal lattice and negative δ34SCDT values (–11.80‰). On the plot of its C1 chondrite-normalized REE abundances, a slightly expressed positive Eu anomaly and high HREE concentrations are observed. The high content of SrSO4 (2.33 to 3.42 wt.%) in the barite crystal lattice indicates hydrothermal parent solutions. The δ34SCDT values of the studied barite are +10.40‰, which is typical for Permian seawater and its δ18OSMOW values range between 15.6 and 17.7‰. A distinct positive Eu anomaly is shown on the plot of the C1 chondrite-normalized REE abundances in barite. Geochemical characteristics of the studied tetrahedrite and barite of Duboki Vagan are very similar to those of previously investigated Glumac and Dubrave-Dugi Dol barite deposits. The fluorite from the Dubrave-Dugi Dol deposits displays a negative Eu anomaly and its Tb/La and Tb/Ca ratios indicate a quite different origin in relation to barite formation. This is all in the accordance with the possible existence of two different paragenetic types of barite deposits in the MBSM and SEB (Southeastern Bosnia), which significantly differ in the δ18OSMOW ranges of their barites and δ34SCDT values of their sulphides. The first type of barite deposits originated in the Late Variscan phase (Lower Permian). It is characterized by numerous Cu, Fe, Zn, Sb, As, Pb sulphides and Cu-Sb-tetrahedrite without mercury, all having positive δ34SCDT values (0 to +5 ‰). Early intercontinental rifting took place between the uppermost Permian and Lower Triassic and enabled, in a great number of barite deposits, (especially in the MBSM), remobilization and partial fluidization of their Fe, Cu, Zn, Sb and Pb sulphides which reacted with ascended mercury, sulphur and fluorine rich mantle fluids and resulted in the formation of Hgtetrahedrite and octahedral fluorite. These processes caused the occurrence of the second paragenetic type of barite deposit with Hg-tetrahedrite as the main ore mineral, but characterized by strongly negative δ34SCDT values.

Discrimination criteria for assigning ore deposits located in the Dinaridic Palaeozoic-Triassic formations to Variscan or Alpidic metallogeny

Abstract Among the ore deposits located in the Palaeozoic-Triassic formations of the Dinarides, siderite (± ankerite) and barite mineralization hosted by Carboniferous and Lower Permian sediments as well as polymetallic deposits in the Mid-Bosnian Schist Mts (MB), caused a long standing dispute concerning their metallogenic affiliation.

Geochemical characteristics and genesis of Mačje Jame and Vranjski Potok As-Cu-bearing iron occurrences west and southwest of the town of Busovača, Mid-Bosnian Schist Mountains

In this study two small, but genetically very interesting iron carbonate deposits Macje Jame and Vranjski Potok, south west of Busovaca (MBSM), located in the pre-Devonian metamorphic complex were investigated in detail. The analyses of the main chemical components, trace elements, REE, isotope composition of C, O, S, 87Sr/86Sr ratio of rhyolite, plot of REE normalized to CI chondrites and a microscopic study of thin and polished sections were performed. Three mineralization phases were identified: the oldest is the main phase (90-95 wt %) with Fe (Ca, Mg, Mn) carbonates (siderite, ankerite, Fe-dolomite) as the predominant minerals whereas magnetite, hematite, albite, allanite, pyrite I, quartz I represent subordinate minerals. The second phase is the pneumatolytic-kathathermal phase (5-10 wt %) characterized by pyrrhotite relicts, pyrite II, quartz II, arsenopyrite and some supposed accessory minerals such as cassiterite, wolframite, gersdorffite, columbite. The youngest is the katha-mezo-epithermal-hydatogene phase (<1 wt %) which gave quartz III-chalcedony as gangue minerals and marmatite, chalcopyrite, boulangerite, gel-pyrite-marcasite, sphalerite, enargite, tetrahedrite, galena, cosalite, bismuth and sternbergite as ore minerals. Almost an identical paragenesis has been found in the oldest ore deposit of the Gemericum Paleozoic metamorphic complex (RADVANEC and BARTALSKY, 1987).The first and second mineralization phase of both ore deposits formed in the Carboniferous from metamorphogeno-hydrothermal fluids generated from S-granitoid magmatic rocks and their protoliths. This claim is strongly supported by very similar REE and their interior disposition between these deposits and metarhyolites as well as by the obtained values of strontium ratios. The third, youngest phase is the product of a very weak overprint of the Late Variscan (290-260 Ma and in the Upper Permian-Lower Triassic (260-240 Ma) time) hydrothermal activity.

Lanthanide Geochemistry and Fluid Inclusion Peculiarities of the Fluorite from the Barite Deposits South of Kresevo (Bosnia and Herzegovina)

Strata-bound barite deposits occur in Devonian dolomites, situated in the Mid-Bosnian Palaeozoic Schist Mountains. These contain barite as the main ore mineral (5.9 wt% SrSO4 on average and d34S= +8.3‰) which comprises 90-99 wt% of the bulk ores. The subordinate components are calcite, fluorite, Hg-Sb-tetrahedrite, pyrite and quartz. Analysis of REE by INAA revealed an extremely low content of lanthanides (1.584 ppm), negative Eu anomalies (Eu3+/Eu+ = 0.7398), and (Tb)N/(La)N = 6.2 indicating late-stage mineralization. Primary fluid inclusions show a uniform number of infilling phases (L+V+S), and persistent volume ratio. This indicates homogeneity of the hydrothermal ore-forming fluids and an absence of boiling phenomena at the time of fluorite formation. Th is between 200° and 310°C, with a distinctive maximum at 250°C. Tfm -20.3°C predominates but careful examinations of the early melting behaviour of the inclusions warrants the existence of Tfm -51°C, and the presence of CaCl2. High salinity between 25 and 26 wt% eq. NaCl was determined from the hydrohalite melting temperature (Tmh). Some additional daughter minerals are also present. Fluorite, barite and calcite formed from the high saline waters probably originated by mixing of heated hydrothermal fluids with the highly evolved post-Variscan Upper Permian formation waters. This is supported by the study of the isotopic composition of the carbon, oxygen and sulphur of the paragenetic carbonates and sulphides.

A Zincian Chrome-Spinel from the Cr-Ba-Fe-Cu-Zn Deposit near Busovaca (Bosnia and Herzegovina)

The metamorphic complex of the Busovaca area is mostly composed of Upper Silurian-Lower Devonian metapelites, metapsammites and metarhyolites formed under low grade metamorphism at 350° to 450°C and 3 to 5 kbars. The ore minerals of the Busovaca deposit are: magnetite (with relics of zincian chrome-spinel), rimmed by ferrichromite, and pyrite, chalcopyrite, enargite, bornite and siegenite. The gangue minerals are: siderite, quartz, albite, hyalophane, muscovite, chromian-chlorite and manganoan ankerite. Proton microprobe analyses (PIXE) were made of samples A (core Ac of the slightly altered chrome-spinel), B (strongly altered chrome-spinel with Bc-core, Bfc-ferrichromite zones, Br-magnetite rim) and C (cryptically zoned magnetite with Cc-core and Cr-magnetite rim). The results are recalculated in formulae, and presented on separate diagrams. The optical investigations, microprobe analyses, beam-scan photographs, diffusion rates of Mg, Al, Zn, Cr, and Mn, and diagrams, allow the following conclusions to be made: (1) magmatic origin of the primary chrome-spinel, (2) the emplacement of the Zn was prior to the alteration under very low f02, most probably synchronous with the sulphide mineralization; (3) the alteration process took place in two phases: (a) the early stage volume-for-volume replacement and formation of the ferrichromite and magnetite zones, (b) the late stage characterized by decolourization and/or resorption, and/or dissolution of the core (patches, specks, “atoll structure”); (4) released Al, Cr, Mn, and Zn have been taken up by silicate, carbonate and oxide minerals forming chromian-chlorite, manganoan ankerite or contaminated siderite and pyrite; (5) the diffusion rates among Al, Zn, Cr, and Mn during different stages of the alteration have the following sequence: Al - Zn - Cr - Mn; (6) the optically unzoned magnetite crystals or aggregates originated in chrome-spinel; (7) the mineral assemblage of the Busovaca deposit co-exists with the surrounding metamorphic complex belonging to the greenschist facies.

Cobalt, nickel, wolfram, cadmium, selenium, silver and gold-bearing mercurian tetrahedrite from the Saski Rad barite-siderite deposit in the Mid-Bosnian Schist Mts.

In the Saski Rad barite-siderite ore deposit, Hg-tetrahedrite is the main ore mineral, pyrite and some others are only accessories. Two tetrahedrite samples (fresh and weathered) have been analysed in detail: major and minor components, constituent trace elements, REE, and δ34SCDT values. The following microconstituents have been detected: Ni 71 ppm (in fresh sample) and 70 ppm (in weathered sample); Co 113 and 90 ppm; Cd 27 and 20 ppm; W 20 and 5 ppm, Bi 2500 and 1613 ppm; Se >100 and 72 ppm and Au 11 and 9 ppm. These values have been compared with the only currently available analysis of Hg-tetrahedrite from the Duboki Vagan near Kresevo in the Mid-Bosnian Schist Mts. (MBSM) carried out by JURKOVIC et al. (2010): Ni 266.2 ppm; Co 63.5 ppm, Cd 319.6 ppm; Bi 1466.0 ppm; Au 38.96 ppm which also agrees with our analysis of Hg-tetrahedrite from the Brixlegg barite deposit in Tyrol, Austria: Co 234.4 ppm; Cd 160.5 ppm; W 6.7 ppm; Sn 1.0 ppm; Bi 909.1 ppm; Se > 100 ppm and Au 2.3 ppm. The δ34SCDT isotope values of six tetrahedrites from the Saski Rad are on average –10.11‰, those of three tetrahedrites from the Duboki Vagan –10,05‰ and of the tetrahedrite from the Brixlegg deposit –1.60‰. The ΣREE content is lower in two analysed tetrahedrites from the Saski Rad deposit (10 ppm) compared to the tetrahedrite from Duboki Vagan (15 ppm) and the tetrahedrite from Brixlegg (17.4 ppm). The analysed barite sample from the Saski Rad deposit does not contain microconstituents typical of Hg-tetrahedrite. The distribution and genetic signifi cance of some trace elements, tetrahedrite microconstituents, REE and siderite isomorphic components in the seven most important genetic and paragenetic types of ore deposits in the MBSM and South-Eastern Bosnia have been commented upon.

Neoproterozoic and Early Palaeozoic metallogenies in the Dinarides, South Tisia, Pelagonides and Serbo-Macedonian Mass

The documented Neoproterozoic rocks and ore deposits are known in the Pelagonides (Central Macedonia) and presumed on the basis of superposition in the Serbo-Macedonian Mass (Lower Complex). Paleontologically documented Cambrian-Ordovician (the Early Paleozoic) complexes are in the Medvednica Mt., the Drina-Ivanjica area (the Golija complex), in the West Macedonia and in the Vlasina Complex (SE Serbia). Presumed Early Palaeozoic complex is situated in the South Tisia, in the Una-Sana area and in the Mid-Bosnian Schist Mts.