SEDIMENTARY CHARACTERISTICS AND METALLOGENIC REGULARITY OF PHOSPHORIC ROCK SERIES AT THE BOTTOM OF CAMBRIAN STRATA IN YANGTZE REGION

The phosphoric rock series at the bottom of Cambrian in Yangtze region are mainly contained in the strata of Meishucunian Age. It is worth studying for the various sedimentary facies, complex phosphoric rock series, great variation of sedimentary thickness and large amount of phosphate resources. Through field survey and comparison study of 13 phosphoric rock series profiles in the area, the sedimentary sequence show that, from bottom to top, the grains change from coarse to fine, from cross bedding, wave bedding and graded bedding to parallel bedding, and the bioclasts decrease to disappear; From west to east, the sedimentary microfacies generally change from shallow gentle slope and deepwater gentle slope to continental slope and deep sea, which control the formation of phosphorites to a certain extent. The carbonate rocks, siliceous rock, phosphorites and some silty clay rock transform into siliceous rocks, carbonaceous shale and nodular phosphorites. The phosphoric rock series in the lower section of Zhongyicun Member of Meishucun Formation in Yunnan, the lower member of Gezhongwu Formation in Zhijin and lower member of Taozichong Formation in Qingzhen of Guizhou are the lower ore beds; while the phosphoric rock series in the upper section of Zhongyicun Member of Meishucun Formation, the upper member of Gezhongwu Formation and upper member of Taozichong Formation are the upper ore beds. The phosphoric rock series in the Niutitang Formation in Jinsha, Xishui, Zunyi, Kaiyang and Zhenyuan of Guizhou, the Liuchapo Formation in Tianzhu and Tongren of Guizhou, the Hetang Formation in Shangrao of Jiangxi and Jiangshan of Zhejiang, and the Mufushan Formation in Nanjing of Jiangsu are the top ore beds.