塔里木盆地寒武-奥陶系烃源岩萘、菲系列化合物单体碳同位素特征  

Stable carbon isotopic characteristics of naphthalene and phenanthrene series in Cambrian-Ordovician source rocks from the Tarim basin

作　　者：林俊峰[1] 张敏 张利红 张小东[1] LIN Jun-feng;ZHANG Min;ZHANG Li-hong;ZHANG Xiao-dong(School of Energy Science and Engineering,Henan Polytechnic University,Jiaozuo 454000,China;Hubei Key Laboratory of Petroleum Geochemistry and Environment,College of Resources and Environment,Yangtze University,Wuhan 430100,China;School of Material Science and Engineering,Henan polytechnic university,Jiaozuo 454000,China)

机构地区：[1]河南理工大学能源科学与工程学院,河南焦作454000 [2]长江大学资源与环境学院油气地球化学与环境湖北省重点实验室,湖北武汉430100 [3]河南理工大学材料科学与工程学院,河南焦作454000

出　　处：《地球化学》2021年第3期273-281,共9页Geochimica

基　　金：国家自然科学基金(41772124);深井瓦斯抽采与围岩控制技术国家地方联合工程实验室开放基金(SJF202007)。

摘　　要：为了揭示塔里木盆地海相烃源岩中芳烃分子同位素的地质-地球化学信息,利用逐步增加试剂极性的方法对芳烃馏分进行了进一步的分离,并利用气相色谱同位素质谱(GC-IR-MS)分析技术测定了萘系列和菲系列的单体碳同位素。分析结果显示,芳烃分子碳同位素分布为−47.5‰~−17.4‰,其中寒武系-下奥陶统烃源岩的碳同位素为−38.2‰~−17.4‰,平均为−26.8‰;其中ML1-1、ML1-2两个样品的碳同位素为−36.8‰~−17.4‰,平均为−25.7‰;中-上奥陶统烃源岩为−47.5‰~−20.3‰,平均−30.6‰。结果表明,萘系列和菲系列化合物整体上表现为寒武系-下奥陶统烃源岩富集13C,而中-上奥陶统烃源岩更富集12C;在受到异常高温作用或过成熟度阶段,成熟度可能对芳烃的分子碳同位素产生较大影响,使其更富集13C。不同样品的二甲基萘系列化合物的碳同位素分布特征相似,暗示其可能具有相似的碳同位素分馏机制。而三甲基萘、二甲基菲系列化合物的碳同位素分布杂乱,暗示其成因来源可能较为复杂。塔里木盆地两套海相烃源岩中1,6-DMN、1,2,5-TMN、1-MP和1,9-DMP的碳同位素存在明显差异,可以对两套烃源岩进行有效的区分。To extract the geological and geochemical information present in stable carbon isotopic ratios(δ13C) of some specific aromatic hydrocarbons in marine source rocks of the Tarim Basin, the aromatic fraction was further separated by gradually increasing the polarity of solvents, and compound-specific isotope analysis was conducted on the naphthalene and phenanthrene series using GC-IR-MS. The results show that the δ13C value of these aromatic hydrocarbons ranges from-17.4‰ to-47.5‰. The Cambrian-Lower Ordovician source rocks exhibited values between-17.4‰ and-38.2‰, with an average of-26.8‰, of which two samples, ML1-1 and ML1-2, showed δ13C values from-17.4‰ to-36.8‰, averaging-25.7‰. The δ13C values of the Middle-Upper Ordovician source rocks range from -20.3‰ to -47.5‰, averaging-30.6‰. These results indicate that the naphthalene and phenanthrene series compounds are enriched in 13 C in the Cambrian-Lower Ordovician source rocks, whereas the Middle-Upper Ordovician source rocks exhibit enrichment of 12 C. Maturity can affect carbon isotope ratios. At abnormally high temperatures or conditions equating to the over-mature stage, aromatic hydrocarbons may become enriched in 13 C. The dimethylnaphthalene(DMN) series in different samples exhibited a similar δ13C distribution, suggesting a similar carbon isotope fractionation mechanism. The δ13C distribution of the trimethylnaphthalene(TMN) and dimethylphenanthrene(DMP) series is chaotic, suggesting possibly complex origins. Finally, there are evident differences in the δ13C values of 1, 6-DMN, 1, 2, 5-TMN, 1-MP, and 1, 9-DMP in the two sets of marine source rocks of the Tarim Basin, which can be used to effectively distinguish these two source rocks.

关 键 词：海相 烷基萘 烷基菲 碳同位素 塔里木盆地 

分 类 号：P593[天文地球—地球化学]