摘要
在岩相学研究基础上,应用有机地球化学、主量及微量元素地球化学分析方法,对鄂尔多斯盆地西缘两口钻井奥陶系乌拉力克组斜坡相页岩沉积环境进行分析,探讨其对有机质富集的影响。研究结果表明:乌拉力克组页岩以石英(平均质量分数为47.5%)和黏土矿物(平均质量分数为24.9%)为主,发育硅质页岩和混合页岩。页岩总有机碳(TOC)含量较低(TOC质量分数平均为0.85%),有机质类型为Ⅰ型,有机质热演化程度达到高成熟阶段(等效镜质体反射率R_(equ)平均为1.42%)。乌拉力克组沉积期古生产力指标w(生物SiO_(2))和w(Ba)/w(Al)显示具有低的古生产力,气候以温暖湿润为主。氧化还原指标(w(V)/w(Cr),w(V)/w(Sc)和w(Ni)/w(Co))及岩相学显示沉积水体为深水贫氧强受限环境。综合分析认为乌拉力克组页岩有机质富集受控于古生产力和较好的保存条件。乌拉力克组有机质含量低的主要原因是古生产力低,而古生产力低可能是沉积期研究区距离火山活动较远、缺乏海底洋流和陆源物质输入较少引起的表层水体营养物质浓度较低所致。
Based on petrography,the organic geochemistry in combination with major and trace elements geochemical methods were used to study the sedimentary environments and their roles in organic matter enrichment mechanism of the Ordovician Wulalike Formation in two wells of slope facies shale in the western margin of Ordos Basin.The results show that quartz and clay(averaging of 47.5%and 24.9%,respectively)are the most abundant minerals,and the lithology is siliceous shale and mixed shale.The shale has low TOC contents(averaging of 0.85%)and type I kerogen,and high maturity stage(mean of 1.42%R_(equ)).Paleoproductivity parameters w(biogenic SiO_(2))and w(Ba)/w(Al)show a low paleoproductivity and the paleoclimate is mainly warm and humid in the Wulalike Formation sedimentary stage.Both redox indexes,such as w(V)/w(Cr),w(V)/w(Sc)and w(Ni)/w(Co)and petrography show a deep-water dysoxic and strongly restricted environment.Comprehensive analysis reveals that the enrichment of organic matter in Wulalike Formation is controlled by paleoproductivity and redox condition.The low TOC in Wulalike Formation is mainly caused by the low paleoproductivity,which may be due to the low concentration of nutrients in surface water caused by the long distance from volcanic activity,the lack of submarine ocean current and less input of terrigenous materials.
作者
张艳妮
李荣西
席胜利
姚泾利
黄何鑫
赵帮胜
吴小力
杨玲
ZHANG Yanni;LI Rongxi;XI Shengli;YAO Jingli;HUANG Hexin;ZHAO Bangsheng;WU Xiaoli;YANG Ling(School of Earth Science and Resources,Chang'an University,Xi'an 710054,China;Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018,China;Shaanxi Geological Survey Experiment Center,Xi'an 710068,China)
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2022年第9期3401-3417,共17页
Journal of Central South University:Science and Technology
基金
国家自然科学基金资助项目(41772118)。
作者简介
通信作者:李荣西,博士,教授,博士生导师,从事油气地质与地球化学方向研究,E-mail:rongxi99@163.com。
