扬子地块西南缘寒武纪梅树村期岩相古地理特征及其对磷矿富集的控制意义OA

To systematically evaluate the resource potential of phosphorite deposits in the Lower Cambrian Meishucun Formation on the southwestern margin of Yangtze Block,detailed sedimentary facies and lithofacies paleogeographic research were conducted based on field outcrop observations and drilling profiles from typical mining areas.By integrating methods from sedimentology,petrology,paleontology,and thin sectiom analysis,the sedimentary facies of the Cambrian Meishucunian stage are classified into supratidal,intertidal,shoal,subtidal,and shallow marine shelf types.Lithofacies paleogeographic reconstruction indicates that during the deposition of the Cambrian Meishucun Formation,water depth gradually increased from west to east across the Yangtze area.Phosphate deposits are mainly developed within the intertidal bay between the Kangdian and Niushoushan ancient lands,in the eastern Yunnan-western Sichuan area.Taking the Yangchang deposit as an example,based on sedimentary microfacies division,the phosphorite rocks are successively classified as sandy dolomitic phosphorite facies,sandy-gravelly dolomitic phosphorite facies,and phosphorus-bearing siliceous dolomite facies.Among these,the sandy dolomitic phosphorite facies represents the highest-grade phosphorite type.Regional lithofacies paleogeographic characteristics suggest that the western margin of the Yangtze Block exhibits greater phosphorite metallogenic part than its eastern part.The Mangbu anticline,east of the Yangchang anticline,is identified as a favorable prospective area for future exploration of large-scale Cambrian phosphate deposits.