Micritic phosphorites in Doushantuo formation are mainly spread in Guzhang, Yuanling, Luxi, Chenxi and Huaihua areas in West-Hunan province, and located in eastern of pericontinerital sea during the Duoshantuo age. Phosphate-bearing sequence consists basically of clay, silica, phosphate and carbonate rock in ascending order. The micritic phosphorite is main type of the phosphate rock.The phosphate minerals in micritic phosphorites are micritic, fibrous and finecrystal apatites. The micritic apatite was directly precipitated from marine water. The fibrous apatite was pricipitated from interstitial water among micritic apatite lumps. The finecrystal apatite was mainly produced by recrystallization of the micritic apatite and formed under the influence of siliceous solution. In addition to apatite, the micritic phosphorite also contain illite, quantz, dolomite and calcite, etc..The micritic phosphorites were in the transitional horizon from the clayay or siliceous to carbonate deposites in Doushantao Formation. In general, they deposited in sedimentary environments of transitional zone.
赵东旭. 1985, 震旦纪陡山沱组的泥晶磷块岩. 地质科学, (4): 381-390.
Zhao Dongxu. MICRITIC PHOSPHORITES IN THE SINIAN DOUSHANTUO FORMATION[J]. Chinese Journal of Geology, 1985, (4): 381-390.