湘中南中奥陶统烟溪组页岩地球化学特征及有机质富集机理  

Geochemistry and organic enrichment mechanism of shale in Yanxi Formation of middle Ordovician in central-south Hunan

作　　者：吴诗情 郭原草[3] 郭建华[1,2] 李智宇 李杰[1,2] 刘辰生[1,2] 王玺凯[1,2] 郭祥伟[1,2] WU Shiqing;GUO Yuancao;GUO Jianhua;LI Zhiyu;LI Jie;LIU Chensheng;WANG Xikai;GUO Xiangwei(School of Geosciences and Info-physics,Central South University,Changsha 410083,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education(Central South University),Changsha 410083,China;College of Civil Engineering,Hunan University of Science and Technology,Xiangtan 411201,China)

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083 [2]有色金属成矿预测与地质环境监测教育部重点实验室(中南大学),湖南长沙410083 [3]湖南科技大学土木工程学院,湖南湘潭411201

出　　处：《中南大学学报（自然科学版）》2020年第5期1255-1267,共13页Journal of Central South University:Science and Technology

基　　金：中国地质调查局地质调查项目(DD20160183);湖南省自然科学基金资助项目(2017JJ1034,2017GK2233)。

摘　　要：为了解湘中南中奥陶统烟溪组黑色页岩有机质富集规律及模式,选择湖南城步撑架坪(CJP)、宁远棉花坪(MHP)、祁东马杜桥(MDQ)这3个剖面的烟溪组页岩样品对有机质丰度、主微量元素质量分数进行测试。研究结果表明:烟溪组有机质丰度较高,CJP黑色页岩TOC质量分数w(TOC)平均为2.52%,MHP黑色岩石w(TOC)平均为1.96%,MDQ黑色岩石w(TOC)平均为2.54%。化学蚀变指数ACI和w(Sr)/w(Cu)显示烟溪组时期为温暖潮湿的气候;生物成因钡w(Baxs)为141.6~738.0μg/g,表明烟溪组沉积环境具有中等生产力;古氧化还原参数w(V)/(w(V)+w(Ni))和w(Th)/w(U)指示水体环境为缺氧-贫氧环境;有机质的富集受古生产力、古地理、海平面变化、陆源碎屑物等多方面因素影响,而闭塞性沉积盆地引起的水体缺氧环境是有机质保存下来的决定因素;烟溪组页岩有机质富集模式是受浊流沉积物影响的"深水滞留盆地"模式,华夏地块浊流沉积物的输入使盆地中部祁东地区的有机质丰度比研究区东南侧的丰度高。To acknowledge the organic matter(OM)enrichment mechanism and pattern of black shale in Yanxi Formation of Middle Ordovician(O2 y)in central-south Hunan,samples from Chengjiaping(CJP)of Chengbu,Mianhuaping(MHP)of Ningyuan and Maduqiao(MDQ)of Qidong were selected to measure mass fractions of TOC,major and trace elements.The results show that OM abundance of O2 y is high.The TOC mass fraction of black shales in CJP,MHP and MDQ is 2.25%,1.96%and 2.54%,respectively The chemical index of alteration ACI and w(Sr)/w(Cu)demonstrates a warm and wet atmosphere.The mass fraction of biogenic Barium is 141.6-738.0μg/g,revealing that the sedimentary enviroment of O2 y has a medium-level paleopnductivity.Paleoredox parameters such as w(V)/(w(V)+w(Ni))and w(Th)/w(U)indicate dysoxic-anoxic environment.The enrichment of organic matter is influenced by many factors,including paleoproductivity,paleogeography,sea level change and terrigenous debris.However,the anoxic environment of water caused by occluded sedimentary basins is the decisive factor for the preservation of organic matter.The pattern of OM enrichment of O2 y is sediments deepwater euxinic style influenced by turbidity.The input of Cathaysian block’s turbidity makes w(TOC)in the middle area Qidong appears more than that in the basin’s southeastern part.

关 键 词：烟溪组 页岩 富集机理 中奥陶统 湘中南地区 

分 类 号：P595[天文地球—地球化学]