寒武系底部含磷岩系中硅质与磷质的关系探讨OA

In the Early Cambrian,a large-scale phosphate deposition event occurred on the Yangtze Platform.A systematic study of the genesis and depositral assemblage of phosphate deposits is not only significant for understanding the early evolution of life on Earth but also beneficial for the exploration and development of modern phosphate resources.This work integrated measuredsection data from the Yangchang area in Zhenxiong County,the Kunyang area in Jinning District,the Lianxing area in Zhijin County,and the Yingchanggou area in Guizhou Province.Petrographic identification and geochemical analysis were conducted on samples from the phosphatic rock series,with a focus on the source of silica in the phosphate deposits,the genesis and classification of the deposits,and the coupling relationship between SiO2 and P2O5 in the phosphatic rock series.The study reveals that in the Cambrian,SiO2 and P2O5 show a strong negative correlation in all four areas,constrained by different paleogeographic and sedimentary environments.In the Yangchang and Kunyang areas,which were close to the ancient land,phosphate depositrals are abundant,and sandy,siliceous dolomite layers alternate with phosphorite layers,with three main phosphate ore intervals present.In the Zhijin area,the lower part of the phosphate ore layer contains siliceous components,while the upper part is predominantly dolomitic,with intermittent phosphate bands.Geochemical data indicate that during the sedimentary period,the phosphate deposits were dominated by terrigenous input;the upper part of the ore-bearing sequence is rich in SiO2,while the dolomite layers are relatively poor in SiO2.Furthermore,the phosphatic rock series in the four areas exhibit a certain degree of coupling,with siliceous layers or siliceous breccia layers present at the base.In some parts of Zhijin,the uppermost ore body corresponding to that in Yangchang is absent or not deposited.The research results provide new insights for understanding the chemical conditions of the Early Cambrian marine environment,the sedimentary model of phosphorite deposits,and the formation mechanism of phosphorite resources,while also holding direct theoretical significance for metallogenic theory research and the deployment of concealed phosphate ore prospecting in the neighboring northwestern Guizhou region.