Study On Genesis And Mineralization Effect Of Black Rock Series Of The Upper Ordovician Tanjianshan Group In The Northern Margin Of The Qaidam Basin

Multiple sets of black rock series are developed in the Tanjianshan Group and adjacent intervals in the northern margin of the Qaidam Basin.These biack rock series are not only high-quality source rocks and low-calorific value fuels,but also the important horizosn for the enrichment of certain inorganic elements.However,the mechanism of the interaction between organic matter and specific inorganic elements,the sedimentary environment and tectonic activities during the formation of black rock series need to be further explored.The thesis analyzed the formation and evolution history of the field surveying structural traces,sedimentary strata,and lithological distribution characteristics of the northern margin of the Qaidam region from a macro level.Based on the geochemical experiment,this thesis analyzed the material source,sedimentary environment,preservation conditions,and evolution process of the black rock series from the micro level.The main achievements and recognitions are as follows:(1)The total organic carbon(TOC)content in the black rock series of the Tanjianshan Group and adjacent sections is relatively low,with an average TOC of only1.5%.The source rock series are at the high-over-maturity stage.The original organic matter content in the sediments of the black rock series were relatively high and the sources of organic matter are mainly low-marine organisms such as algae and microorganisms during this sedimentary period.and the types of organic matter are mainly type ? and type ?₁.(2)The black rock series of Tanjianshan Group and adjacent sections are mainly composed of argillaceous and silty sediments,and the clay minerals in the mineral components are extremely high,with an average value of more than 50%.The main elements mainly include Si O₂,Al₂O₃ and Fe₂O₃,and the average content of Si O₂exceeds 50%.V,Cr,Sr,Ba,Mo,U and other elements in trace elements have obvious enrichment characteristics compared to the average content of the crust.Co,Ni,Cu and other elements show the characteristics of relative losses;the overall content of rare earth elements is relatively high,showing obvious characteristics of relatively enriched light rare earth elements and relatively depleted heavy rare earth elements.The enrichment of V,U and other elements is greatly affected by terrigenous volcanic debris and hydrothermal activity.(3)The black rock series of the Tanjianshan Group and its adjacent sections were formed in the environment of the post-arc basin under the transition condition of marine to terrestrial facies.The overall water retention degree of depositional environment is relatively high,and the paleoproductivity is relatively high,under the conditions of reduction-weak reduction evolution.(4)The formation of the black rock series in the Tanjianshan Group and adjacent sections is the result of a gradual evolution during a long period of geological history.The interaction between organic matter and metal elements took place from the source of the parent material,enrichment,burial,mineralization to denudation.Throughout the entire sedimentary evolution process,and their dynamic evolution characteristics of dynamic evolution have emerged along with changes in sedimentary environment and burial conditions.