Discussion on the Sedmeatary Environment of the Phosphorus Bearing Rock Series in the Xingshenbao Phosphorus Deposits

The Xingshenbao phosphorus deposits locates in the westein Hubei Province and phosphorite is presented in the middle and lowar Doushantuo Formation of Sinisn System. Thickness of the rock series bearing phosphorus is 12. 4 -473.5m and the rock series bearing phosphoras consisis of dolomite bearing manganese, botia, mud stctie, phosphorite and dolomite. The phospholite thickness is 1. 9-17. 6m and the average content of P₂O₅ is 22. 80%. According to saditagry sheractaristics of the cook series bearing phosphorus is divided into three region of sedimentary facies. They are shallew besin facics in Wawu, lagoon facies in Zhengjiahe and tidal flatfacies in the Tangzhaying. The industrial phosphorites scdirnented in the shallow basin and lagoon and consists of comular spharolth , alga and bacteria granula , shelly granula and stromatolite etc. . which have been produced by organisnis and biochemical activity as have been accumulted in the orginal phace. It is controled that origin of phosphorus and organisms activity, therefore only forms lean min-earls or does't form mineral in the tidal. The Tangzhaying - Paiguoping palaeo-rise controls the time and space distribution of phosphorite in region. Researches of petrology and geochemistry indicate there is a lagoon circumstance with hypersaline during the early period of the rock series bearing phosphorus and the tidal flat circumstance in the late period, which is affected by the leaching action of fresh water. During the early period for the formation of phosphorite are the shallow basin and lagoen with the lower energy, which forms algal met phosphorite, algal and bacteria one and pelletal one. During the late period for the formation of phosphorite are algal hill and bank, which forms stromatolithic phosphorite and slelly granule one. The firsh phosphorus ore bed (Ph₁) sedimented in reducing circcnstance and the second one (Ph₁) in week oxidation. The rock series bearing phosphorus is a regression sedimenting scquece under whole transgre-sion condition.