云南晋宁梅树村下寒武统砾屑磷块岩的扫描电镜研究

通过扫描电镜观察.发现云南梅树村中谊村段砾屑磷块岩中的磷质砾屑主要由磷质鲕球、磷质微球和磷质雏晶堆积体组成.磷质微晶是磷酸盐的基本晶体.磷质雏晶是在扫描电镜下所能观察到的最小的磷酸盐颗粒,但它们晶形不完全.砾屑磷块岩的形成过程可以分为三个阶段:磷质鲕球、微晶和雏晶形成阶段,磷质砾屑形成阶段,和砾屑磷块岩形成阶段.磷质砾屑的形成环境为浅水近岸,水动力条件不稳定,沉积速率和通量不高.

ELECTRON MICROSCOPE STUDY ON PEBBLE PHOSPHORITES OF MEISHUCUN SECTION,JINNING, YUNNAN PROVINCE

The microstructure and composition of phosphahic pebbles in phosphorites in Zhongyicun Member of Meishucun Section, Jinning, Yunnan Province have been carefully investigated by electron microscope. The investigations revealed that the composition of pebble phosphorites can be divided three different levels: pebble phosphorites consist of phosphatic pebbles and cement materials; phosphatic pebbles consist of phosphatic oolites, phosphatic microglobules and phosphatic amorphous aggregates are composed of phosphatic microcrystals and amorphous grains and non-phosphatic micrograins.The phosphatic amorphous grains and microcrystals are the most fundamental amd the smallest grains of phosphatic matters possibly observed under electron microscope. By the investigations of electron microscope, the followimg three stages of formation of pebble phosphorites are proposed: (1) Stage of formation of phosphatic amorphous grain aggregates and phosphatic microcrystals which were crystallized out from sea water; (2) Stage of formation of phosphatic pbbles; (3) Stage of formation of pebble phosphorites. The sedimentary environment of pebble phosphorites belongs to neritic deposit