The Study Of Mechanism Of Organic Matter Affecting Migration And Enrichment Of Phosphorus And Uranium In Black Rock Series Of The Lower Cambrian In Tongren,Guizhou

The lower Cambrian black rock series in Tongren is rich in phosphorus,uranium and other minerals,and the content of organic matter is generally high.In order to explore the role of organic matter in the mineralization process,based on detailed field investigation,this paper reveals the source of organic matter and the degree of thermal evolution through rock and mineral identification,TOC test of total organic carbon,chloroform asphalt"A"extraction and group component analysis,GC-MS analysis of saturated hydrocarbons and aromatic hydrocarbons,major,trace,rare earth elements and inorganic carbon isotope test,so as to explain the sedimentary environment of phosphorus bearing rock series and analyze the mechanism of organic matter participating in mineralization.The main achievements are as follows:（1）The TOC content of phosphorous rock series is high,and the content of phosphorous block rock is higher than that of phosphorous rock.The organic matter is closely related to P and U,and the organic matter in the ore is mostly distributed in the concentration area of collophanite.（2）N-alkanes,terpenoids,carbon dominance index CPI of n-alkanes,hopane and sterane characteristics,C₂₇-C₂₈-C₂₉sterane trigonometric diagram all indicate that organic matter comes from low aquatic organisms such as eukaryotic algae living in plankton;The 20S/（20S+20R）values,Ts/Tm values,methylphenanthrene index（MPI）,ratio of（non-hydrocarbon+asphaltene）to（alkane+aromatics）,odd-even dominance index of n-alkanes（OEP）and disterane characteristics all reflect high maturity of organic matter;Pr/Ph value,trifluorene series trigonometric diagram,properties of hopane of C₃₁-C₃₅,Ni/Co and V/（V+Ni）values all indicate that the organic matter was formed in a depositional environment with strong reduction.（3）Organic geochemical indices,δEu,Cr/Zr values,and inorganic carbon isotopeδ¹³C values all indicate that the source of some phosphorus is consistent with that of organic matter,but more phosphorus and uranium are derived from deep hydrothermal fluids.（4）The influence of organic matter on the migration and enrichment of phosphorus and uranium is mainly reflected in three aspects:preservation adsorption-fixation of phosphorus and uranium,transformation of environment-maintenance of complexation migration,provision of materials-promoting precipitation and mineralization.（5）The involvement of organic matter in the migration and enrichment of P and U mainly goes through three stages:seafloor ejection--P/U source,sea level rise--P/U upwelling,and environmental anoxia--P/U precipitation.