滇东磷块岩的成因类型

GENETIC TYPES OF PHOSPHORITE IN EASTERN YUNNAN

研究滇东地区下寒武统底部磷块岩,发现了五大类十五个种属的藻类化石。它们是磷块岩的主要组成,对磷块岩的形成起了主导作用,因而提出生物成磷的成矿机理。根据成磷作用特点和矿石成分、结构、构造特征等,划分出三种磷块岩成因类型:原生菌藻磷块岩,内碎屑磷块岩与次生磷块岩。

Five types of fossil algae (fifteen genera) have been distinguished in thin sections from the early Cambrian phosphorites in East Yuanan. In fact, fossil algae constitute the main composition of phosphorites, playing an important role in their formation. In terms of mineral composition, ore texture and genetic characteristics, the East Yunnan phosphorites are classified into three genetic types: l,primary algae-bacterial phosphorite, which was formed through absorbing and concentrating sea water phosphorus by algae-bacterial and microfauna; 2, intraclastic phosphorite and 3, secondary phosphorite, which were formed through mechanical winnowing or secondary leaching at expense of the primary algae-bacterial phosphorite.Secondary enrichment and concentration of phosphate in these types are observed.