With the methods of chemical analysis, mineralogical analysis, isotopic analysis and observation under microscope and scan electric microscope (SEM) in combination with knowledge of field work, black shale-hosted concretionary phosphates were investigated so as to get the detailed information of their structure and composition, and then to reveal formation mechanisms. The results showed that the evident microbic activities were characteristic of the concretions, and indicated microbes played an important role in phosphate precipitation. From these results we concluded that biomineralization was the essential power for formation of concretionary phosphates in black shale. According to these phenomena we could also infer that the growth of concretionary phosphates were initiated by microbic activities which created neutral or weak alkaline microenvironments favoring phosphate precipitation. In the mean time the growing process of concretionary phosphate were influenced by evolution development of physic-chemical condition of sedimentary porous medium.
Lei Jiajin,Li Renwei,Cao Jie. THE CHARACTERISTICS OF BLACK SHALE-HOSTED CONCRETIONARY PHOSPHATES AND THE MECHANISMS OF MICROBES MEDIATED PHOSPHORUS PRECIPITATION IN CAMBRIAN HORIZON ON YANGTZE PLATFORM[J]. Chinese Journal of Geology, 2000, (3): 277-287.