盐湖页岩有机质富集主控因素及模式  

Main Controlling Factors and Modes of Organic Matter Enrichment in Salt Lake Shale

作　　者：孙中良 王芙蓉[1] 侯宇光[1] 罗京 郑有恒[2] 吴世强[2] 朱钢添 Sun Zhongliang;Wang Furong;Hou Yuguang;Luo Jing;Zheng Youheng;Wu Shiqiang;Zhu Gangtian(Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences,Wuhan 430074,China;Research Institute of Exploration and Development,SINOPEC Jianghan Oilfield Branch Company,Wuhan 430223,China)

机构地区：[1]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石化江汉油田分公司勘探开发研究院,湖北武汉430223

出　　处：《地球科学》2020年第4期1375-1387,共13页Earth Science

基　　金：国家科技重大专项资助项目(No.2017ZX05049-005);国家自然科学基金资助项目(No.41772143)。

摘　　要：为深入研究盐湖背景下的江汉盆地潜江凹陷潜江组34段第10韵律及4下段部分韵律层的页岩有机质富集机理,采用X荧光光谱(XRF)、碳硫仪、GC、GC-MS等手段,研究该地区页岩的元素变化与TOC富集之间的关系,以此探讨有机质富集的主控因素,从而建立有机质富集模式.结果表明,潜江组页岩有机质在水进体系域(TST)中相对较为富集,在高位体系域(HST)及低位体系域(LST)中较为贫乏;潜江组页岩有机碳与古生产力指数(P/Ti)、古气候指数(Mg/Ca)、古水深指数(Rb/K)大致呈正相关,随古盐度指数(Sr/Ba)值的增加先增大后减小,与陆源物质输入量参数(SiO2、Al3O2)呈负相关.页岩层段中古生产力指数(P/Ti)大于1、古盐度指数(Sr/Ba)介于2~4、古气候指数(Mg/Ca)小于0.4,古水深指数(Rb/K)大于0.007且陆源物质输入较少,有机质富集.研究揭示,潜江凹陷潜江组页岩有机质来源主要为水生生物,水进体系域中,在较为潮湿的古气候条件下,水生生物繁盛,陆源碎屑输入量低,对有机质的稀释作用减弱;同时,较多的降水使湖水深度快速增加,表层水体盐度降低,湖底盐度较大,形成盐度分层,增强深部古水体的还原性,有利于有机质的富集.In order to further study the enrichment mechanism of the 10 rhythm of the third(Eq3)members(Eq3410 for short)and partial rhythm of the forth(Eq4low)members shale organic matter in the Qianjiang Formation of the Qianjiang sag,Jianghan basin under the background of salt lake,X-ray fluorescence spectroscopy(XRF),carbon sulfur analyzer,GC,GC-MS and other methods were used to understand the relationship between elemental changes and TOC enrichment of shale in this area,so as to analyze the main controlling factors of organic matter enrichment and establish organic matter enrichment mode.The results show that organic matter is more concentrated in the transgressive systems tract(TST),and is poor in the highstand systems tract(HST)and the lowstand systems tract(LST).Organic carbon is positively correlated with paleoproductivity index(P/Ti),paleoclimate index(Mg/Ca)and paleo-water depth index(Rb/K),and the organic matter increases first and then decreases with the increase of the ancient salinity index(Sr/Ba).Land-based material input and the quantitative parameters(SiO2,Al3O2)are negatively correlated with organic carbon.And when P/Ti>1,20.007 and the input of terrigenous matter is less,the organic matter is more concentrated.The study reveals that the source of organic matter in the shale of the Qianjiang Formation in the Qianjiang sag is mainly aquatic organisms.Under the relatively humid paleoclimate conditions,the aquatic organisms prosper,and the input of terrigenous debris is low,which weakens the dilution of organic matter.At the same time,more precipitation makes the lake water depth increase rapidly,the surface water body salinity decreases,and the lake bottom salinity is larger,which results in salinity stratification and enhances the reduction of deep lake water and is conducive to the enrichment of organic matter.

关 键 词：盐湖 潜江凹陷 沉积环境 古生物类型 有机质富集机理 有机质沉积模式 地球化学 

分 类 号：P595[天文地球—地球化学]