THE CARBONACEOUS ROCKS IN CRETACEOUS DEPOSITS OF THE KAMCHATSKY MYS PENINSULA: GEOCHEMISTRY, METAL ACCUMULATION AND SEDIMENTATION CONDITIONS
УГЛЕРОДИСТЫЕ ПОРОДЫ В МЕЛОВЫХ ОТЛОЖЕНИЯХ П-ОВА КАМЧАТСКИЙ МЫС: ГЕОХИМИЯ, МЕТАЛЛОНОСНОСТЬ И УСЛОВИЯ НАКОПЛЕНИЯ

O.L. Savelyeva, Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences, D.P. Savelyev, B.G. Palesskii, Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences, V.S. Sobolev Institute of Geology and Mineralogy of SB RAS
2021 Tikhookeanskaya Geologiya  
In the Cretaceous paleoceanic deposits of Eastern Kamchatka, carbonaceous beds have been studied, the origin of which relates to the oceanic anoxic events. In carbonaceous rocks, the contents of trace elements and noble metals: Ba, Cu, Ni, Zn, Mo, V, U, Y, Au, rare-earth elements and platinoids are increased in comparison with the hosted jaspers and limestones. In particular, the Au content in ash-laden carbonaceous rocks reaches 0.8 ppm, and Pt 2.1 ppm. The geochemical proxies Mo/Mn and V/(V +
more » ... es Mo/Mn and V/(V + Ni) indicate the accumulation of carbonaceous deposits in euxinic conditions. The significant non-lithogenic excess Ba indicates a high bio-productivity in the upper part of the water column. High bio-productivity and euxinic conditions of sedimentation caused the enrichment of carbonaceous rocks with many trace elements. Phosphorus trapped into the sediments with bone detritus, which subsequently sorbed rare-earth elements and yttrium from sea water during its fossilization. Copper, zinc and vanadium are associated with the Fe-sulfide phase (framboidal pyrite). Noble metals accumulated during sedimentation and early diagenesis were deposited with organic matter and/or directly from seawater. In carbonaceous rocks, they appear to be in the form of organometallic compounds or enter into the composition of framboidal pyrite. The sedimentation occurred at the top of a seamount in the Pacific Ocean. The studied deposits are similar to the Cretaceous sediments that formed at the tops of seamounts in the northwestern Pacific, where carbonaceous beds are also present in the sections. Organic-rich sediments were deposited within the oxygen minimum zone during periods of maximum bio-productivity of plankton.
doi:10.30911/0207-4028-2021-40-3-41-53 fatcat:sf6nvh7yyrashjd7v6m7oxrgsm