In the scope of this research, the petrographic and geochemical analyses of clastic sedimentary rocks from the St. Barbara, copper and iron ore mine in Rude near Samobor, have been made, aiming to classify and determine the provenance and environment of formation of clastic sedimentary rocks, as well as the influence of hydrothermal fluids on their properties. Eight samples were collected in total from different locations in the mine. Six of those samples have been studied in detail. The results showed structural and geochemical variability and uneven hydrothermal alteration intensity in the samples. Based on petrographic analyses, three rocks are classified as sublithoarenite, quartz arenite and quartz greywacke. Three of the samples are classified as ore breccia, ore sandstone, and ore silt-sandstone due to the pronounced hydrothermal alterations and ore mineralisation. Comprehensively, petrographic and geochemical analyses indicate that the source rocks of the investigated clastic sedimentary rocks were felsic (La/Sc = 0.9-6.2; Th/Sc = 1.3-2.4), most probably sedimentary, possibly resedimented rocks. The extent of source rock weathering was very high (Chemical Index of Alteration CIA = 52.1 - 81.3 %) and the geotectonic position of the sedimentary basin was very likely to be at the passive continental margin.
In Palaeozoic rocks of South-eastern Bosnia (SEB) there are numerous, but very small vein and replacement barite ore deposits containing up to 10% Pb-Zn-Fe-Cu sulphides. Their geochemical characteristics are compared with large barite monosulphide (Hg-tetrahedrite) ore deposits in Mid-Bosnian Schist Mountains (MBSM). The 87 Sr/ 86 Sr isotope ratios in the barites of both areas are very similar, (0.710972 and 0.714170 in SEB, 0.711764 and 0.712548 in MBSM), and indicate the epigenetic hydrothermal origin of the barite ore deposits. This conclusion is supported by the elevated Sr content in barites of both areas (0.48 to 2.83% in SEB, 1.44% in MBSM) and the δ 13 C and δ 18 O values in calcite and siderite of barite ore deposits which are shifted toward lower values relative to typical values occurring in the Devonian host rock. The δ 18 O values in barites from SEB (+14.2‰ to +15.6‰) are remarkably lower than those from MBSM (+15.8‰ to +22.4‰). This can be explained by the lower temperature and lower salinity of mineralisation fl uids in barite ore deposits of SEB. The δ 34 S values in barites of SEB are positive (+11.6‰ to 17.7‰), and enriched in heavy sulphur isotopes in comparison with sulphides of SEB (-0.41 to +4.26‰), whereas those in tetrahedrites are negative indicating two remarkably different sulphur sources and times of formation. Barite ore deposits of both areas, SEB and MBSM, have been genetically linked to fl uids that originated during Late Variscan S-type magmatism and metamorphism of Upper Proterozoic and Lower Palaeozoic rock complexes. However, later Post Variscan/Eoalpine heating processes affected signifi cant parts of barite ore deposits in MBSM. They caused fl uidization of sulphides in barite deposits, ascension of subcrustal deepseated fl uids enriched in H 2 S and mercury (± fl uorine), which passed through Upper Proterozoic and Caledonian ore deposits amalgamating their Au and Ag content leading to formation of a new mineral, Hg-tetrahedrite rich in Au (10-50 g/t) and Ag (1000 do 3000g/t).
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