| In this paper,the phosphate rock of the Lower Cambrian Yuhucun formation of Xundian and Dawan in eastern Yunnan is taken as the research object,the drilling core cataloguing and systematic sampling based on 17 pieces,combined with thin slice identification,scanning electron microscope and energy dispersive analysis,principal element analysis and trace element analysis,etc.The composition,occurrence characteristics and controlling factors of phosphate rock in this area were studied.The phosphorite in the study area mainly developed in the second stage of Yuducun formation,including upper and lower ore beds.Its chemical components are mainly CaO,P2O5,SiO2,MgO and acid insoluble,among which P2O5 is between818%and its grade is not high,the main phosphorus-bearing minerals are carbon-fluorophosphatite（apatite）,non-phosphorous minerals are calcite,dolomite,quartz,clay minerals and carbonaceous,etc.The upper layer is mainly composed of mud crystal structure,and the lower layer is mainly of granular structure.According to the structure,the types of phosphate rock in the study area are coarse strip phosphate block,block phosphate block,fine strip phosphate block,granular phosphate block and breccia phosphate block.According to the characteristics of lithology,there are four lithofacies types of carbonate rock,siliceous rock and phosphorous block rock in Yuducun formation,and the Yuducun formation is mainly formed in the confined surface tidal flat environment,and the high energy shoal between the intertidal and the subtidal is conducive to the formation of phosphorite.Phosphorite is mainly occurring in argillaceous siltstone and mudstone is stratified.The occurrence characteristics of upper and lower ore beds are analyzed and the mechanism of ore-forming enrichment is discussed.The formation of phosphate rock in the study area is mainly affected by biological action,hydrothermal process,sedimentary environment,diagenesis and geotectonics,etc. |
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