辽宁秀水盆地早白垩世义县组有机质富集机理研究——以LFD1井为例  

Mechanism of Organic Matter Enrichment of Lower Cretaceous Yixian Formation in the Xiushui Basin,Northern Liaoning Province:A case study of well LFD1

作　　者：胡祖宏 胡建芳[1,2] 席党鹏 孙守亮[4] 陈树旺[4] 彭平安[1,2] HU ZuHong;HU JianFang;XI DangPeng;SUN ShouLiang;CHEN ShuWang;PENG PingAn(State Key Laboratory of Organic Geochemistry,CAS Center for Excellence in Deep Earth Science,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Beijing),Beijing 100083,China;Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China)

机构地区：[1]中国科学院广州地球化学研究所,深地科学卓越创新中心,有机地球化学国家重点实验室,广州510640 [2]中国科学院大学,北京100049 [3]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [4]中国地质调查局沈阳地质调查中心,沈阳110034

出　　处：《沉积学报》2024年第1期282-294,共13页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41790452,41688103)。

摘　　要：【目的】辽宁北部秀水盆地为中生代小型断陷盆地,发育沉积厚度巨大的下白垩统义县组地层,需要明确其有机质富集方式。【方法】通过对秀水盆地LFD1井义县组二段和三段沉积岩开展了有机质稳定碳同位素组成以及正构烷烃、甾烷和藿烷等生物标志化合物的有机地球化学研究。【结果与结论】秀水盆地LFD1井义县组二段和三段沉积岩有机质含量高,变化范围为0.01%~4.78%,且已经进入成熟阶段,具有良好的油气勘探前景;其有机质沉积演化划分为四个阶段:阶段Ⅰ,火山活动促进了生产力水平的提高,在弱还原—弱氧化的条件下形成了δ^(13)C_(org)偏轻、有机质含量高的沉积记录;阶段Ⅱ1,δ^(13)C_(org)偏重的陆生植物碎屑大量进入湖泊中,沉积环境处于强还原状态;阶段Ⅱ2,沉积环境在还原—弱氧化状态下变化,湖泊水体中藻类和水生植物繁盛,提供大量有机质促使形成了高TOC的沉积建造;阶段Ⅲ,沉积速率加快,对有机质富集起到了一定稀释作用,但该阶段的开始和结束出现了短暂的强还原沉积环境和水体分层,并在对应层位形成了有机质相对较高的沉积记录。[Objective]The Xiushui Basin,located in northern Liaoning,is a small faulted basin formed in the Me-sozoic,and developed the Lower Cretaceous Yixian Formation with large sedimentary thickness.It is of great impor-tance to understand the mechanism of organic matter enrichment.[Methods]In this study,sediment samples were collected from well LFD1.Total organic carbon(TOC)content,stable carbon isotopic composition(δ^(13)C_(org))and the distribution of molecular markers(aliphatic hydrocarbons,steranes and hopanes)from members 2 and 3 of the Yixi-an Formation were analyzed.[Results and Discussions]The results show that the TOC ranged from 0.01%to 4.78%,and the organic matter was mature.The vertical variations of the bulk organic parameters(TOC andδ^(13)C_(org))and biomarker indices indicated that the profile could be divided into four stages.Stage I:The initial content was en-hanced by volcanic activity that enabled the depostions of great amount of organic matter and lowδ^(13)C_(org) values.Stage II1:Highδ^(13)C_(org) values suggest increased input from land plants.The biomarker indices show a relatively anoxic envi-ronment at this stage.Stage II2:The sedimentary environment is anoxic-weakly oxic.Algae and aquatic plants flour-ished in the lake,and the abundant organic matter facilitated the deposition of organic-rich source sediments.Stage III:A more rapid sedimentation rate diluted the abundance of organic matter.However,water column was stratified and lake evolved into anoxic environment at the beginning and end of this stage,which favored high organic matter content deposition.

关 键 词：义县组 生物标志化合物 沉积环境 有机质来源 

分 类 号：P618.13[天文地球—矿床学]