Sedimentary Sequences of Phosphorites in Western Hubei Province

The phosphorites of Doushantuo Formation of Sinian System are mainly distributed in the Xingshenbao, Jinxiang and Yichang prefectures of Western Hubei Province. There are two main industrial ore beds, i. e., Ph1 and Ph2. According to the characteristics of texture and structure as well as material components of phosphorites, on the sedimentary section we've divided the ore bed into argillaceous striped phosphorite ( I ), argillacecus onyx one (II). dolomitic striped one (III) and compact block one (IV) from the bottom to the top. They are naturally piled up together and form the I - II -III-IV sequences in macro-structure and the different textures of phosphorites are also regularly and naturally piled up in the microcosmic sequences, gel-phosphorite (A), cumularspharolith one (B) and shelly granular one (C) from lower to upper and they form an A-B-C microcosmic sequence. We've sumed up characteristics about the macroscopic and microcosmic sequences and researched the inner link among them in the paper and there is also a inner link between the phosphorus granule type and matrix or cement in the microcosmic sequence. On the basis of the developmental degree of the sedimentary sequence of phosphorite we've divided 3 sequential types of integrated and incomplete as well as no-order ones and sumed up the relationship between the sequential type and industrial tenor of the phosphorous. The characteristed sedimentary sequence of phosphorite exists universally but owing to the influence of many factors such as palaeogeography. sedimentary circumstance and microorganism activity etc. , the integrity and developmental degree of phosphorite is different from each other in different mineral areas. The researchs indicate that the macroscopic sequences are obviously controlled by the sedimentary circumstance and palaeogeography, for example, in the palaeogeographic unit of shelf back-ground from the Western Hubei to the Middle Guizhou provinces the incomplete- type sequence has been formed in the deeper water basin facies, but no-order-type formed in the shallow water higher energy zone of upwarded district, the intergraded-type did in the clinoform zone between the above two and it is the best district to pile up the main industrial mineral body. The microcosmic sequence is controlled by the microorganism activities and is a product of the microorganism periodical activities in the same circumstance. The phosphorite sequence not only has a theoretical significance to research mineralization, enrich regular patterns of mineral and cause of formation of mineral deposit of phosphorite, but also has a directive one to prospect and explore mineral as well as evaluate mineral deposits of phosphorits.