断层与幔源二氧化碳气藏的形成和分布——以渤海湾盆地济阳坳陷为例  

Faults role in formation and distribution of the mantle derived carbon dioxide gas pools: Case study of the Jiyang Depression in Bohai Bay Basin,China

作　　者：李理[1] 钟大赉[2] 杨长春[2] 赵利[1] 

机构地区：[1]中国石油大学(华东),青岛266580 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石学报》2016年第7期2209-2216,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40772132)资助

摘　　要：幔源CO2气的形成和分布与不同级别断层早白垩世以来的活动密切相关。郯庐断裂带是研究区最主要的成气断层,拆离断层和变换断层这些地壳断层是次要的成气断层,二者于早白垩世143Ma、124Ma、新生代-43Ma、-24Ma和-8Ma的走滑或伸展活动,以及与之准同时的新生代碱性玄武岩浆活动,控制了幔源CO2气的分散和聚集。它们与基底断裂、盖层断裂共同组成运移通道,其中拆离滑脱处的低速带和盖层断裂中的顺层断层是重要的水平运移通道。早白垩世古太平洋板块俯冲脱水脱气,产生的幔源CO2气沿着郯庐断裂带向上分散聚集;新生代以来受控于太平洋板块俯冲方向和速度的改变以及印欧板块碰撞的远程效应,形成幔源CO2气。与此同时郯庐断裂带切割深度亦逐渐加大,-43Ma碱性岩浆活动亦开始形成幔源CO2气并主要位于断裂带,24Ma和8Ma（5Ma）为新近纪碱性岩浆活动脱气两个主要形成时期。郯庐断裂带的活动使地幔脱气形成的CO2沿断层走向向上运移,并在作为重要横向运移通道的拆离断层拆离滑脱处,与因岩浆脱气形成的CO2汇合,再通过陡倾斜、缓倾斜基底断层、盖层断层的接力传递在浅部聚集成藏。预测郯庐断裂带附近是无机成因油气重要的聚集分布区带。The formation and distribution of the mantle derived CO2 gas pool has great relationship of the faults. The mantle derived CO2 was mostly induced by mantle degassing by paleo Pacific Plate subduction in Early Cretaceous 143 Ma and 124 Ma,partial melting and upwelling of mantle in - 43 Ma,24 - 15 Ma,and 8 - 4Ma. Also the degassing by alkaline basalt magma in - 43 Ma,24 - 15 Ma,and 8 - 4Ma generated many mantle derived CO2. They dispersed and accumulated by different level faults. The Tanlu Fault,lithospheric fault of the study area,is the most important fault to gas ＇s dispersion and accumulation,while the crustal fault like detachment faults and transfer faults acted as secondary important faults to the gas dispersing and accumulation. The shear or extension of these faults in Early Cretaceous 143 Ma and 124 Ma,Cenozoic - 43 Ma,24 - 15 Ma,and 8 - 4Ma as well as the synsimultaneously alkaline basalt magma action controlled the formation,migration and accumulation of the mantle derived CO2 gas. Different level faults intersected and formed channel to gas,while the detached depth of the detachment faults（ where is also the low velocity zone developed） and the decollément faults transferred by the disconformity and unconformity in cover are very important horizontal channels. In Early Cretaceous,mantle degassing CO2 by plate subduction dispersed and accumulated along the Tanlu fault. Controlled by the change of subduction direction and rate of the Pacific Plate to Eurasian Plate,mantle degassing CO2 induced by partial melting of the mantle migrated along the Tanlu Fault. Meanwhile,the Tanlu Fault cut gradually deeper into the mantle in - 43 Ma,24Ma and8Ma（ or 5Ma）,which induced mantle magma degassing and derived CO2 gas. The mantle degassing CO2 gas migrated upwards along the fault due to Tanlu Fault＇s strike slipping in Cenozoic,and converged to those gases from magma degassing in detached zone（ also the low velocity zone）. Then these gases migrated horizontally through the low velocity zone to the

关 键 词：断层 幔源二氧化碳 形成机制 新生代 渤海湾盆地 

分 类 号：P542[天文地球—构造地质学]