Geochemical and mineralogical research of carbonate minerals at Nizna Slana - mano deposit (Gemericum, Western Carpathians)

Fe-carbonates were formed as products of exchange reactions between the limestone and a fluid phase (open system) with Fe,Mg,Ca,CO2. Carbonate, sulphide and stable isotope (C,O) analyses show mineral associations: 1.calcite1 + pyrite1 + ?graphite 2.Mg-ankerite + Fe-ankerite + sideroplesite + siderite + pyrite2 + phengite + tetrahedrite + arsenopyrite + ?graphite + calcite + quartz. The second (metamorphic) association was formed on the relies of the first one. Pyrite1 is dispersed in carbonate. The younger pyrite2 grows on the cores of pyrite1, it is disseminated in carbonates, or forms clusters. The presence of Mn2+ in pyrite2 indicates its metamorphic origin with carbonates. Carbon derived from limestones played a decisive role in the formation of Fe-carbonates. Minor amounts of carbon may attributed also to the organic carbon, derived from the rocks surrounding the limestones. Isotopic values of the source fluid (δ13C = -0.1 to -0.3 % PDB; δ18O = +1.0 to +1.4 %, SMOW) shows its metamorphic origin. Crystallization began in the sediments, calcite was altered to Mg-ankerite (T = 300 - 350 grad C) later to Fe-ankerite, finally terminated bu the formation of sideroplesite and siderite (T = 200 grad C), from the same fluid. (authors)