Ozernoe massive sulfide deposit of SEDEX-type in Early Cambrian intravolcanic island arc depression: Genetic features and isotopic evidence (Eastern Siberia, Russia)

摘要

The largest Ozernoe massive sulfide deposit is located in Early Cambrian intravolcanic island arc depression and characterized by many features of SEDEX-type deposits. Mineralization occurs as a series of twelve undeformed near-horizontal sub-parallel tabular and sheet-like ore-bodies in the third order brachy-syncline depression filled with the tuffaceous-terrigenous-carbonate turbidites. Reef limestones, heterometric sedimentary breccia with the sulfide and red hematitic jasper clasts are present in the deposit. Carbonaceous shales are not abundant. Ores of the deposits were formed in a relatively shallow subaqueous environment under high energy conditions. Ores precipitated from the supersaturated brine pool on the sea floor. Macro-textures of sedimentary deposition and early diagenesis are universally present. The feeder zones have not been defined in the footwall. Long-lived and pulsed brine exhalation processes in forming the deposit are revealed. The heavy sulfur isotopic compositions of sulfide minerals (δ~(34)S +8.8/ +23.7per thousand) are due to deeply circulated marine water and thermochemical reduction of seawater sulfates. Carbon of hydrothermal-scdimentary siderite has a homogeneous and lightly isotopic composition (δ~(13)C_(PDB) -0.5 / - 1.2per thousand).