摘要
碱湖相烃源岩中有机质来源复杂,会形成丰富且复杂的甾类化合物。通过对玛湖凹陷二叠系风城组17件代表性碱湖沉积物进行气相色谱—质谱与单体烃同位素分析并结合前人研究成果,详细分析了其中丰富的甾烷类化合物的分布特征,并讨论了其主控因素。结果表明:风城组沉积物中含有极低丰度的C 27规则甾烷和极高丰度的C_(28)和C_(29)规则甾烷,这可能是由于沉积物中一些绿藻种属特殊有机质贡献的结果。所分析样品中的重排甾烷相对丰度较低,这可能与风城组沉积物中低含量的黏土矿物有关。风城组沉积物中低丰度的烷基甾烷可能与特殊的有机质来源有关,同时也可能是与高盐度的沉积环境有关,特别是相对于C_(29)4-甲基甾烷和C_(30)甾烷,含有低丰度的C_(28)4-甲基甾烷。来自于古湖泊边缘区的样品中,C_(30)24-正丙基胆甾烷丰度较高,可能指示着该地区风城组烃源岩有机质中有红藻的生物来源贡献。此外,在风城组沉积物中检测并鉴定了高丰度的羊毛甾烷,表明风城组沉积时期高盐度的沉积水体条件,并推测其生物来源可能是蓝绿藻,但不排除其他特殊藻类的贡献。高丰度的C_(28)和C_(29)规则甾烷和β-胡萝卜烷可能也指示着特殊绿藻种属的贡献。特殊的有机质贡献造成了三芳甲藻甾烷的缺失。综上,高盐度的沉积水体条件、特殊的有机质来源及低含量的黏土矿物组成,导致风城组碱湖沉积物中丰富且复杂的甾烷类化合物分布。
Steroids in the geological records is generally relevant to the organic matter source;in return,the distributions of steroids would provide unique insights to the organic source in sediments.Organic matter input in the alkaline sediments is complex,which can form various steranes.In this study,a total of 17 cores were sampled to carry out GC-MS and GC-IR MS to investigate the distributions of steranes and their controlling factors by combination of previous reports.Low Pr/Ph combined with high content β-carotane,C_(23) tricyclic terpane and gammacerane indicates a high-salinity water body during deposition of the Permian Fengcheng Formation.The samples are characterized by low abundance of C_(27) regular sterane and high abundance of C_(28) and C_(29) regular steranes,which is due to the contributions from some special organic matter input such as green algae.The content of diasteranes in the selected samples is very low due to the low clay content.A low alkyl-steranes present in the Fengcheng Formation source rocks,which may be affected by organic matter source as well as strongly reducing environment as shown a low C_(28)4-methyl sterane relative to C_(29)4-methyl steranes and C_(30) sterane.Occurrence of C_(30)24-n-propyl cholestane in the Fengcheng Formation samples located in edge of paleo-lake may imply the organic matter contribution from red algae.Moreover,high contents of lanosteranes have been detected in the samples,which suggests a reducing sedimentary environment and a green-algal source as supported by abundant C_(28) and C_(29) regular steranes and β-carotane.The absence of triaryldinosterane in the samples is likely ascribed to some special organic matter source and a low contribution of dinoflagellates.In summary,it is the strongly reducing environment,distinct organic matter input,as well as low clay content in mineral compositions that lead to the various and complex steranes distributions pattern in alkaline sediments.
作者
王东勇
陈践发
李美俊
王文强
肖洪
邹贤利
孙彪
秦慧强
WANG Dongyong;CHEN Jianfa;LI Meijun;WANG Wenqiang;XIAO Hong;ZOU Xianli;SUN Biao;QIN Huiqiang(State Key Laboratory of Petroleum Resources and Engineering,College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;Civil and Environmental Engineering Department,University of Alberta,Edmonton AB,T6G 2H5,Canada;Faculty of Petroleum,China University of Petroleum-Beijing at Karamay,Xinjiang Karamay 834000,China;School of Geoscience Science and Engineering,Xi'an Shiyou University,Xi'an 710065,China)
出处
《古地理学报》
北大核心
2025年第4期1026-1043,共18页
Journal of Palaeogeography:Chinese Edition
基金
国家自然科学基金青年科学基金项目(编号:42202134)
新疆维吾尔自治区自然科学基金项目(编号:2023D01A20)
国家留学基金委项目(编号:CSC202306440129)联合资助。
关键词
甾类化合物
古环境
有机质
碱湖
风城组
二叠系
玛湖凹陷
准噶尔盆地
steroids
palaeoenvironment
organic matter source
alkaline sediments
Fengcheng Formation
Permian
Mahu sag
Junggar Basin
作者简介
第一作者:王东勇,男,1998年生,博士研究生,主要从事有机地球化学和油气勘探研究。E-mail:dywang0907@163.com;通讯作者:李美俊,男,1972年生,教授,博士,主要从事有机地球化学和油气勘探研究。E-mail:meijunli@cup.edu.cn。
