Geochemical characteristics and genesis of

In this study two small, but genetically related iron carbonate deposits Mačje Jame and Vranjski Potok, south west of Busovača (MBSM), located in the pre-Devonian metamorphic complex were investigated in detail. 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 identifi ed: 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, haematite, albite, allanite, pyrite I, quartz I represent subordinate minerals. The second phase is the pneumatolytic-kata-thermal phase (5-10 wt %) characterized by pyrrhotite relicts, pyrite II, quartz II, arsenopyrite and some supposed accessory minerals such as cassiterite, wolframite, gersdorffi te, and columbite. The youngest is the kata-meso-epithermal-hydatogene phase (<1 wt %) which gave quartz III-chalcedony as gangue mineral and marmatite, chalcopyrite, boulangerite, gel-pyrite-marcasite, sphalerite, enargite, tetrahedrite, galena, cosalite, bismuth and sternbergite as ore minerals. An almost identical paragenesis has been observed in the oldest ore deposit of the Gemericum Palaeozoic metamorphic complex (RADVANEC and BARTALSKY, 1987). The fi rst and second mineralization phase of both ore deposits formed in the Carboniferous from metamorphogenohydrothermal fl uids 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 strontium ratios. The third, youngest phase is the product of a very weak overprint of hydrothermal activity in the Late Variscan (290-260 Ma) and in the Upper Permian-Lower Triassic (260-240 Ma).