湘西磷块岩的岩石地球化学特征及成因

晚震旦世、早寒武世是我国扬子区重要成磷时期,自滇东至湘西分别发育了台地型、过渡型和盆地型磷矿床,其中以盆地型成磷条件研究程度稍差。本文采用GC-MS、ICP-MS、形态硫分析、硫同位素、物相分析等多种实验方法研究了湘西上震旦统、下寒武统磷块岩的形成条件。从磷的来源、磷的沉积和富集等方面,探讨了盆地型磷块岩的成因。结论认为湘西磷块岩为生物、有机质聚磷作用的成矿模式。有机质主要来源于藻、菌类生物。海底热泉活动提供了丰富的磷。在缺氧的环境条件下,有机质为磷的聚集和转化提供了条件。

THE GENESIS AND GEOCHEMISTRY CHARACTERISTICS OF PHOSPHATES OF UPPER SINIAN-LOWER CAMBRIAN, WEST HUNAN

The late Sinian and early Cambrian is very important epoch of phosphate formatio n in Yangtze, China. It is distributed platform, transition and basin- type phos phate deposits from west Yunnan to west Hunan, and it is very poor research on t he basin- type phosphates. The analysis methods include the ICP-MS, GC-MS, isoto pe, organic carbon and micropetrology. Advances have been made in the following aspects: The phosphate of black shale of the upper Sinian - lower Cambrian gener ated from the anoxic event, and the organic matter source is algae and fungal. T he organic matter can be preserved well under the anoxic environment, and especi ally for the lipids. Phosphorite deposits are controlled by the sea-level change , and the ore-bearing sets developed in the transgressive systems tract and cond ensed section. The author analyzed the anoxic environment and the source of orga nic matter on the basis of the biomarker parameters. The phosphorus is from hot spring on the bottom of the sea floor, and organism and organic matter accumulat e it. The basin phosphorie generated from the physical migration and the biologi c accumulation.