摘要： 湖相碳酸盐岩产状多样,多以夹层形式分布在碎屑岩剖面中,也见以结核或钙质微体化石等薄层赋存于泥岩、页岩等碎屑岩中,具有层数多、单层薄、呈韵律性变化等特点。受构造背景、物源输入和古环境等因素控制,中国湖相碳酸盐沉积最早出现于二叠纪,主要发育时段为古近纪,具有沉积时间跨度大、分布面积广的特征。湖相碳酸盐岩按成因可分为原生沉积型、成岩改造型和热液喷流型3类。中国湖相碳酸盐岩的碳氧同位素特征可揭示原生和成岩过程中水介质环境的差异性: (1)δ¹³C和 δ¹⁸O 密切相关,且δ¹³C多正偏,指示封闭型咸水、半咸水湖泊环境;(2)δ¹³C和 δ¹⁸O 无相关性,且δ¹³C多负偏,指示开放型湖泊环境;(3)δ¹³C严重正偏,指示成岩作用时发酵带的环境受到古细菌参与的甲烷生成作用的影响。

关键词: 碳酸盐岩, 碳氧同位素, 开放型湖泊, 封闭型湖泊, 发酵带, 甲烷生成

Abstract: Lacustrine carbonate rocks have various occurrences. They commonly occur as the interbeds in clastic rocks with characteristics of multi-layers,thin individual layer and rhythm. Occasionally,they occur in mudstone and shale as thin layers of concretions or calcareous microfossils. Controlled by tectonic background,provenance and palaeoenvironment,the lacustrine carbonate rocks in China show wide spatial-temporal distribution,which were firstly reported in the Permian,but mainly found in the Paleogene. Based on carbonate and oxygen isotope analysis,different water environments during primary deposition and diagenetic process are concluded: (1)Well-related δ¹³C and δ¹⁸O with mostly positive δ¹³C values,indicating a closed saltwater or semi-saltwater lake environment;(2)Completely-unrelated δ¹³C and δ¹⁸O values with mostly negative δ¹³C values,indicating an open lake environment;(3)Seriously-positive δ¹³C values,indicating that during diagenesis,the environment was affected by the methane generation process,which was participated by archaebacteria.

Key words: carbonates rock, carbon and oxygen isotope, open lake, closed lake, fermentation, methanogenesis

中图分类号: 

• P597+.2