川西南乌斯河古油藏Re-Os年龄及其对峨眉山大火成岩省火山活动的响应  

Re-Os Dating of the Wusihe Paleo-Reservoir and Its Response to Emeishan Large Igneous Province Actvities in the Southwest Sichuan Basin

作　　者：佟傲 高亚仙 Tong Ao;Gao Yaxian(Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences,Wuhan 430074,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国地质大学资源学院,湖北武汉430074

出　　处：《地球科学》2023年第2期568-581,共14页Earth Science

基　　金：国家自然科学基金面上项目(No.41672140);湖北省自然科学基金创新群体项目(No.2021CFA031);国家大学生创新创业训练计划项目(Nos.202110491024,S202210491185,S202210491024)。

摘　　要：在盆地形成演化的漫长过程中,岩浆的侵入、深部高温流体上涌等热事件会导致盆地存在热异常,从而对油气的生成演化起重要的控制作用.位于四川盆地西南部峨眉山大火成岩省中带的乌斯河上震旦统至下寒武统古油藏是开展火山作用与油气成藏演化关系研究的理想对象.针对该古油藏,论文开展了沥青镜质体反射率和有机元素含量分析以及Re-Os同位素测年工作,并结合前人相关钻井埋藏史、热历史以及峨眉山大火成岩省的研究成果,揭示了沥青的成因和演化,探讨了乌斯河油气成藏作用与火山活动的联系.研究结果表明:乌斯河古油藏沥青具有较高的沥青反射率(~2.27~2.77)及较低的H/C原子比(0.21~0.22),成因为经历了热裂解作用形成的焦沥青;沥青Re-Os同位素等时线年龄为~262 Ma,记录了原油热裂解、天然气生成的时间.对比四川盆地内部及川东北地区上震旦统至下寒武统油气成藏的关键时刻,乌斯河地区~262 Ma较早的原油裂解时间与邻区H1井异常的热事件时间(~260 Ma)、峨眉山大火成岩省的形成时代(257~263 Ma)近于一致.这表明乌斯河地区油气成藏作用受同期大火成岩省火山活动的控制,焦沥青的形成及其Re-Os同位素年龄是对峨眉山超级地幔柱活动的响应.研究从年代学的角度建立了四川盆地火山活动、异常热事件、烃源岩异常热演化与原油裂解天然气生成之间的联系,为峨眉山大火成岩省的油气成藏效应研究提供了一个典型实例.During the long process of basin formation and evolution, thermal events such as magma intrusion and deep high temperature fluid upwelling will lead to thermal anomalies and directly control the petroleum evolution. Located in the inter-mediate zone of Emeishan large igneous province in southwest Sichuan Basin, the Upper Neoproterozoic-Lower Cambrian Wusihe paleo-reservoir is an ideal object on revealing the relationship between volcanism and the petroleum evolution. Integrating the bitumen reflectance(Rb), elementary composition and Re-Os isotope dating in this work as well as the burial history, thermal histories and key timings related to Emeishan large igneous province from published works, the origin and evolution of bitumen were discussed and the relationship between petroleum accumulation and volcanic activity was established in the Wusihe area. The high bitumen reflectivity( ~2.27-2.77) and low H/C atomic ratio( 0.21-0.22) of the solid bitumen indicate they are high maturity pyrobitumen formed by thermal cracking. The Re-Os dates(~262 Ma) of the solid bitumen recorded timing of crude oil cracking and gas generation. In addition, the nearly same timing among the oil cracking, abnormal thermal event revealed by H1Well(~260 Ma), as well as the Eruptive time for the Emeishan igneous province(257-263 Ma) indicate the petroleum evolution in the Wusihe reservoir is controlled by volcanic activities in the Emeishan igneous province during the same period, and the formation of the pyrobitumen and its Re-Os isotopic age are the responses to the activities of the Emeishan super mantle plume.This study provides a typical example for the study of petroleum evolution effect in Emeishan large igneous province.

关 键 词：古油藏 沥青 RE-OS同位素定年 火山作用 峨眉山大火成岩省 石油地质 

分 类 号：P618.13[天文地球—矿床学]