Study On The Sedimentary Geochemical Of Datangpo Formation And Chemical State Of Ocean In Songtao Area

The stratum is completely developed and well preserved between late Neoproterozoic and early Cambrian in south China.The region of the major research findings caused the attention of geological scholars both at home and abroad,makes it become the international classic areas for early life evolution research.The research of marine chemical state of Nanhua Period is great significance for evolution of the biological and metallogenic regularities in Neoproterozoic.On the basis of predecessors' study,through the sampling on field geological section and well drilling,by means of XRD,scanning electron microscope?SEM?and X-ray fluorescence spectrometer,this paper analysis the petrology characteristics,main and trace geochemical characteristics and iron composition,sulfur isotope characteristics in pyrite of the rock of Datangpo Formation.And the geochemical characteristics and sedimentary environment of Datangpo Formation was researched,the chemical state of the ancient marine environment was analyzed.It is marine facies sediment that the sedimentary facies of Datangpo Formation,Nanhua Period,in Songtao of south China.The main rock types is the carbonaceous shale,the containing manganese carbonaceous shale,siliceous rocks and a set of manganese mineralization beds,which formed in the anoxic and undisturbed water environment.The main rock types are shale,silty shale,sand shale of the second and third section of Datangpo Formation.Quartz and clay minerals are the highest levels of minerals in rock samples in the study area.The ratios of n?Al₂O₃?/n?Al₂O₃ + Fe₂O₃?reflect that the sedimentary characteristics was ocean deep-sea sedimentary of manganese ore,and was obvious continental margin sedimentary of surrounding rock;The ratios of n?SiO₂?/n?Al₂O₃?reflect that the terrestrial source was mainly composed of sediment source and there was certain hot water deposit,which mainly influence the formation of the manganese ore;The ratios of Sr/Ba reflect that the rock formed in deep water environment,the depositional environment was shelf to the platform edge slope transition of the second and third parts of Datangpo Formation,which the formed water depth was shallower than the first part;The ratios of Rb/Sr reflect that the manganese ore formed in hot climates,the surrounding rock formed in the dry climate,and the fluctuation of climate change was obvious;The research of redox indicator of U,V,Mo and so on show that the forming environment of the first part of Datangpo Formation was stronger hypoxia environment,and the manganese ore,the second and third parts of Datangpo Formation were weak hypoxia-reduction environment of Datangpo Formation,Nanhua Period,in Songtao of China.The date of iron components and sulfur isotope of Datangpo Formation,Nanhua Period show that the first part of Datangpo Formation formed in the anoxic environment of iron,surrounding rock of it formed in hypoxia environment of sulfide,and oxidation of water began to appear in the environment of the second and third without sulfide water.Composited of geochemical features,iron components and sulfur isotope data and sedimentary environment of Datangpo Formation,Nanhua Period,it is concluded that the marine chemical state of Datangpo Formation,Nanhua Period in China conforms to the "Sandwich" marine chemical model in south China basin of late Neoproterozoic,which the surface is oxidized water and the deep is anoxic water of iron,and between them existed of dynamic vulcanized water in local area of shallow sea.