Study On Sedimentary Environment Of Black Rock Series Of Ediacaran-Cambrian Slope Facies In Eastern Guizhou

In recent years,geologists have carried out a lot of research on the slope facies black rock series and their related minerals,and have achieved a series of important achievements,but most of the research lacks vertical and horizontal sedimentary environment evolution comparison.Therefore,the Laobao Formation-Niutitang Formation section of Sansui and Tongrenbahuang in eastern Guizhou under the continuous Ediacaran-Cambrian deposition was selected to carry out systematic mineralogy and petrological research.At the same time,the content of major elements,trace elements and rare earth elements was determined by analytical testing methods such as ICP-MS,so as to compare and analyze the sedimentary characteristics and element enrichment characteristics,and to explore the evolution law of the sedimentary environment,which can further explore the Cambrian explosion of life.And the theories such as the genetic mechanism of black rock series type deposits provide the basis.Through the research,the following conclusions have been mainly obtained:(1)The black rock series in Sansui and Bahuang belong to slope facies deposits,but the Laobao Formation of Sansui has high silicon and argillaceous content,and has deposited vanadium deposits with industrial value.Conversely,the Laobao Formation in Bahuang has a higher content of dolomites and forms vanadiumbearing siliceous rocks.The P2O5 content and Eu anomaly of the phosphate rock in the Niutitang Formation of Sansui are lower than those of the phosphate rock in Bahuang,but the loss on ignition and clay mineral content are higher,indicating that the large input of terrigenous materials is unfavorable for phosphorus enrichment,and Intense hydrothermal activity contributes to the enrichment of phosphorus.(2)In the black rock series of Sansui and Bahuang,there are scattered granular pyrite,calcite veins,quartz veins,pyrite veins and horizontal bedding.It shows that the marine environment of the black rock series was relatively restored,the water body was deeper,and the tectonic activity was stronger.(3)Ce outliers,U/Th,Ni/Co,V/(V+Ni),V/Cr,V/Sc,Sr/Ba,Al2O3/Mg O values,and paleosalinity index m,etc.It reflects that the Sansui black rock series was generally formed in the semi-deep sea,deep sea or stagnant sea with sulphidationanoxic,semi-arid climate-humidity,brackish water,and only in the formation period of phosphate rock at the bottom of Niutitang Formation,the climate was relatively dry,The water is shallow.It shows that the brackish water environment with sulfidationdeficient oxygen,climate temperature and humidity,and deep water body is conducive to the formation of vanadium ore.(4)The environment of the black rock series in the Bahuang area changed greatly during the deposition,and the redox conditions,paleo-salinity,paleoclimate,and paleo-water depth changed extremely synchronously.During the(including)siliceous dolomite stage in the lower part of the Laopu Formation and the phosphorus rock at the bottom of the Niutitang Formation,the water became more oxidized,the seawater salinity became higher,the climate became arid,and the water depth became shallower.It is revealed that the oxygen-poor-oxidative,arid-semi-arid climate,and the coastal,shallow-semi-deep-sea environments with normal seawater salinity are more conducive to the enrichment of phosphorus.