摘要： 以前的微生物岩识别和分类只根据裸眼可见的中观结构,而对显微镜下的微观结构未予使用。微生物的显微结构有什么基本特征,是否可以用于微生物岩的识别和分类是本文关注的焦点。作者从微生物岩形成机制和实际材料的观察来探讨这个问题。在诱导钙化实验中观察到,蓝藻鞘丝藻Lyngbya的胶鞘表面有碳酸盐矿物形成: 先是在胶鞘表面形成点状碳酸盐颗粒,后来碳酸盐几乎包裹整个丝体,形成一个矿物壳。微生物岩形成的模式推演表明,微生物岩一般都有微生物留下的孔(模孔)和包围模孔的矿物壳2种基本单元。对3个地点的现代微生物碳酸盐岩和1个地点的古代(寒武纪)微生物岩的观察,发现在显微尺度上都具有模孔,此外还可能有矿物壳或胶结物。模孔的形状、大小、排列方式是微生物碳酸盐岩显微结构研究的核心内容,在今后的研究中可以用于微生物岩的识别和分类,以及作为分析形成机制和形成环境的基础。

关键词: 微生物碳酸盐岩, 微生物岩, 显微结构, 模孔, 矿物壳, 基本凝块

Abstract: Previously microbialites were identified and classified based only on mesofabrics,i.e.,the fabrics visible to naked eyes,but not on the basis of microfabrics,i.e., the fabrics visible under the microscope. This paper focuses on the basic characteristics of microfabrics of microbial carbonates and microbialites,and whether they can be used for their identification and classification. An experiment on microbe-induced calcification that we conducted shows that among a variety of microbes,only the filaments of the cyanobacterium Lyngbya form carbonate minerals on the surface of their sheaths,firstly as scattered carbonate particles,and finally as crusts almost enveloping the whole filaments. It is thus proposed that the microbial carbonates that are formed by induced precipitation have two basic constituents,namely,the mold holes,i.e.,the holes left by the microbes,and the carbonate crusts. Microscopic observations of the modern microbial carbonates from the Shark Bay of Australia,Highborne Cay of Bahamas,and Atoll of Kiritimati and the Cambrian dolomitized microbialites in Xinjiang,China revealed that mold holes and the crusts or cements between the pores are a basic characteristic. The shape,size and arrangement of the mold holes and proclots are the core contents of the study on the microfabrics,and these features can be used for the identification and classification of microbialites,as well as the basis for the analysis of their formation mechanism and environments.

Key words: microbial carbonate, microbialite, microfabric, mold hole, carbonate crust, proclot

中图分类号: 

• P588.24+5