大巴山造山过程有机流体研究  

Features and formation of organic fluids during Dabashan orogenesis

作　　者：李荣西[1,2] 董树文[3] 张少妮[1,2] 朱瑞静[1,2] 夏彬[1,2] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]长安大学西部矿产资源与工程地质教育部重点实验室,西安710054 [3]中国地质科学院,北京10037

出　　处：《南京大学学报（自然科学版）》2012年第3期295-307,共13页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(41173055);国家地质调查项目(1212011121117)

摘　　要：野外调研和显微镜下岩相学观察研究表明,大巴山构造带不同构造单元有机流体类型多样,特征各异.北大巴山冲断-推覆构造带发育变质流体包裹体和大量有机流体包裹体.大巴山前陆构造和前陆坳陷区发育三期有机流体包裹体,即液态烃包裹体、纯气态烃包裹体以及储层沥青和古油藏沥青,它们记录了大巴山造山过程中油气形成和演化历史有机流体包裹体甲烷气δ13 C1为-17.036‰～-30.390‰,δD为-107.712‰～-156.730‰,表明其为油型运移天然气.有机地球化学分析表明,大巴山断裂带运移沥青和古油藏沥青原始有机母质以低等水生生物和藻类有机质来源为主,与下寒武统碳质泥岩烃源岩和下二叠统碳酸盐岩烃源岩具有亲缘关系.结合构造演化特征研究认为,印支构造运动之前,大巴山构造带古生代烃源岩在正常埋藏热演化作用下形成液态烃,印支碰撞造山使液态烃大规模运聚成藏,燕山构造运动形成大巴山前陆并伴随古油藏破坏,同时使大巴山前陆坳陷区液态油热解形成天然气藏.大巴山造山过程有机流体研究表明,大巴山前陆不但有天然气成藏过程,而且有液态烃形成和成藏历史.Field investigations along with detailed petrographic observations show that plentiful organic fluids with different characteristics and various occurrences developed in different tectonic units in the Dabashan foreland belt. Large amounts of organic fluids inclusions together with metamorphic fluid inclusions were found in the northern Dabashan thrust-nappe belt. However, organic fluids in the Dabashan foreland belt and the foreland depression were marked with three stages of organic fluid inclusions： the earliest stage of liquid hydrocarbon inclusions, the intermediate stage of pure gaseous hydrocarbon inclusions and the last stage of solid bitumen inclusions. Tbesethree stages organic fluid inclusions recorded formation and evolution history of oil/gas during orogenesis of Dabashan foreland bell. Isotopic analysis to fluid inclusions contained by calcite veins filled in fractures show that δ^13 Ci of organic gas in fluid inclusion was --17. 036‰ -- 30. 390‰ and δD was --107.712‰--156.730‰, which indicated that the gas captured by veins was migrated natural gas. Organic geochemical analysis to bitumen with different occurrences indicated that original organic matter of bitumen in Dabashan foreland belt was mainly the lower aquatic organisms and algae. Lower Cambrian carbonaceous mudstone and Lower Permian carbonate were the most possible source rocks of bitumen. Combined with tectonic evolution history of Dabashan foreland belt, this research proposed that liquid oil was generated from the Paleozoic source rocks in Dabashan area under normal burial thermal conditions before lndosinian orogeny hut accumulated to form paleo reservoirs during Indosinian collision between the North China block and the Yangtze block. The paleo reservoir was destroyed to become reservoir bitumen during Yanshan tectonic when Dabashan foreland belt formed. At the same time, liquid oil in Dabashan foreland depression was pyrolyzed to transform co natural gas. It indicated that there was not only natural gas hut also liquid o

关 键 词：有机流体 有机包裹体 沥青 前陆构造 大巴山 

分 类 号：P542.2[天文地球—构造地质学]