BIOGENIC SEDIMENTATION FACTORS OF ORE FORMATION IN THE NEOPROTEROZOIC STRATA OF THE BAIKAL-PATOM REGION
V.K. Nemerova†, A.M. Stanevichb, E.A. Razvozzhaevaa, A.E. Budyaka and T.A. Kornilovab
aA.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul.Favorskogo 1a, Irkutsk, 664033, Russia
bInstitute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
Keywords: Mineralization model, sediment genesis, back-arc basin, bacteria, carbonaceous sediments, gold, Neoproterozoic, southeastern Siberia
Pages: 572-586
Abstract
The formation environments of stratiform ore deposits in the Neoproterozoic Baikal-Patom region (BPR) have been considered. A model for the formation of the Sukhoi Log gold ore deposit in the Bodaibo zone has been put forward. The first stage is gold concentration by a chemolithotrophic bacterial community. Independently established facts suggest that bacterial communities might also have contributed to initial metal accumulation in the sediments of the Kholodnaya Pb-Zn deposit. The ore beds occur in the high-carbon sediments of the side and trough of the back-arc basin. Sedimentation (Dal'nyaya Taiga and Zhuya regional horizons) took place during the "back-arc basin - foreland basin" transition. This transition is characterized by increased sediment bioproductivity, which is clearly evidenced from the increased biophile-element content and taxonomic diversity of organic remains. Hundreds of microfossil sites in the Neoproterozoic BPR host littoral benthos (cyanobacteria and brown algae) and plankton (green algae). Most microfossils in the outer shelf, on the basin side, and in its trough belong to chemolithotrophic bacteria. These bacteria are assumed to have accumulated metals in the vent field of the back-arc basin. Studies showed the ability of microorganisms (bacteria, algae, fungi, etc.) to accumulate Fe, Mn, Au, Pb, Zn, and other metals. Bacterial communities are particularly important for metal accumulation in the vent fields of rift zones and areas of arc volcanism. All these conditions were observed in the Neoproterozoic BPR.
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