摘要： 依据鲕粒的形态、结构及方解石组成,将豫西宜阳地区寒武系馒头组鲕粒灰岩中的鲕粒分为4种类型: 不规则放射状泥晶鲕粒、泥晶套亮晶表皮鲕粒、同心放射状泥晶鲕粒和规则放射状微亮晶鲕粒。这些鲕粒多由泥晶方解石组成,且泥晶方解石可出现在鲕粒的不同部位,从而与研究区张夏组的鲕粒明显不同,后者由亮晶方解石组成。在电子显微镜下,鲕粒中的泥晶方解石表现为六边形蜂格和片状壁,而这种结构被认为是细菌或蓝细菌的细胞结构,是由附着的微小晶粒呈切向围绕细菌或蓝细菌排列所致。构成蜂格结构的矿物主要为碳酸钙,其被认为是蓝细菌死亡后灰泥化的结果。由此可见,鲕粒中泥晶方解石的形成与微生物的生命活动密切相关,这对于阐明鲕粒在其形成过程中受到微生物的影响具有重要意义。

关键词: 河南省, 寒武系, 鲕粒, 泥晶方解石, 丝状体, 微生物成因

Abstract: The ooids in oolitic limestones of the Cambrian Mantou Formation in Yiyang area,western Henan can be divided,based on their mophology, structures and calcite composition, into 4 types,such as irregular radial micritic ooids, micritic envelope bright crystalline epidermis ooids,tangential-radial micritic ooids and regular radial microsparry ooids. They are mainly composed of micritic calcites that can be found in the different positions of ooids. These ooids are obviously different from those in the Zhangxia Formation that consist of sparry calcites. Under the SEM,the micritic calcites in ooids display hexagonal honeycomb texture and flake wall which are considered to be the cell structure of bacteria or cyanobacteria and the result of tangential arrangement of attached tiny grain around them. The mineral of honeycomb texture is mainly composed of calcium carbonate which is considered to be the result of cyanobacteria disintegration. The above features indicate that the micritic calcites in ooids are closely related to microbial activities,which is of great significance to elucidate the oolitic genesis affected by microbes.

Key words: Henan Province, Cambrian, ooids, micritic calcites, filaments, microbial genesis

中图分类号: 

• P588.24+5