Abstract: The early Cambrian phosphorite deposit in the Gezhongwu Formation, Zhijin County, Guizhou Province, P.R. China is a super large ore deposit combined with phosphorus and REE. Based on the analysis of the chemical and mineral composition of this phosphorus rock series, we focus on the analysis of the phosphorite structures’ characteristics using scanning electron microscope (SEM) and electron probe microscopic analyzer (EPMA). Vertically, it shows that the upper section of silicious phosphorite possesses mud-crystalline structure, clastic structure, amorphous structure and bioclastic structure with lower maturity and sea water from a relatively deep level; and that the lower section dolomitic phosphorite bore clastic structure, amorphous structure and bioclastic structure with higher structure maturity, a stronger hydrodynamic effect and sea water from a relatively shallow level. Horizontally, the Gezhongwu Formation corresponds with the Yuhucun Formation in stratigraphic chronology, both of which have the same structural characteristics. In addition, combined with other sedimentary environment redox indexes, it indicates that the phosphorite deposit formed in the suboxic-anoxic waters and evolved in an environment that was from the coast to a shallow sea.

Keywords: Guizhou; Zhijin; the Early Cambrian; phosphorite structure; sedimentary environment

Email: liujie@mail.gyig.ac.cn

ACTA MINERALOGICA SINICA Vol. 36, No. 2, 2016, Page 253-259