准噶尔盆地南缘泥火山系统的甲烷释放与固碳作用研究

Mud volcanoes are some kind of geological bodies with surfacey characteristics similar to magma volcanoes such as the migration and eruption pathways and the cone on the surface, which are normally formed by release of geological fluids including gases, oils, water, clay and sands from deep reservoirs. There are always micro-seepages around mud volcanoes. The mud volcanoes and their surrounding seepages constitute a complex system of oil-gas releasing with scientific significance in energy recourse and atmospheric environment etc. The mud volcanoes including Dushanzi, Aiqugou and Baiyanggou in south margin of the Junggar Basin will be the targets for this study. The flux of methane will be checked in-situ using gas collection box connected with Metrex sensor, and the sources and generation type of the gases will be identified using chemical composition of the gases and isotopic ratio of carbon and hydrogen of hydrocarbons such as methane. Some alteration mechanism of the solid rocks by hydrocarbons including methane in the mud volcano system will be studied through the petrological, mineralogical and geochemical properties of the erupted mud, host rock of gas emitting pathways and the surrounding setting rocks. The geochemical studied will be performed on the major elements and their chemical species and also implicated to explain the transformation process of methane, the precipitation of secondary carbonate minerals, and the mechanism of carbon fixation in the mud volcano system. All these results will contribute some supporting to evaluate methane releasing, chemical transformation and the contribution to atmospheric greenhouse effect from the mud volcano system.

泥火山是地下深部气体、水和泥砂等地质流体泄漏至地表后形成的外貌与火山锥相似的地质体，其周边常存在油气微渗漏现象，构成复杂的油气逸散体系，具有能源、资源和气候环境等多个方面的科学研究意义。本项目以准噶尔盆地南缘的独山子、艾维沟、白杨沟等泥火山及其周边微渗漏体系为对象，原位测量甲烷等气体排放通量，并通过气体组分和甲烷等烃类碳氢同位素测定，判识气体来源和成因类型。通过喷溢泥浆、气体释放通道围岩和背景地质样品的岩石学、矿物学、元素同位素组成和化学种的对比分析，探讨泥火山逸散甲烷等烃类物质对固体岩石的蚀变作用机制。结合铁、锰、硫细菌与嗜甲烷菌的协同作用研究，阐明泥火山油气体系甲烷等烃类气体在地下运移渗漏系统中的转化过程和次生碳酸盐矿物的沉淀机理与固碳作用。为合理评价泥火山油气逸散系统中的甲烷释放、转化，以及对大气温室效应的贡献提供科学依据。

泥火山是地下深部气体、水和泥砂等地质流体泄漏至地表后形成的外貌与火山锥相似的地质体，其周边经常存在油气微渗漏现象，构成复杂的油气逸散体系，具有能源、资源、灾害和气候环境等多个方面的科学研究意义。项目获得批准资助后，所有研究计划的实施都很顺利、各项工作情况正常。主要工作包括：1）利用皂膜流量计和封闭集气箱连接甲烷探测器，先后两次对独山子泥火山正在活动的泥浆喷口及其周边有限范围原位测量了甲烷等气体排放通量，计算结果显示，泥火山影响地区的土壤微渗漏占绝对优势；2）气体组分和甲烷等烃类碳氢同位素组成特征显示，独山子、艾奇沟、白杨沟等泥火山的气体为来源于侏罗系煤系地层的热裂解气；3）喷溢泥浆、气体释放通道围岩和背景地质样品的岩石学、矿物学、元素同位素组成和化学种的对比分析结果显示，这些泥火山系统存在复杂的油-气-水-岩相互作用；4）独山子泥锥剖面的孢粉组合以浅颜色的新生代分子占比95%，中生代白垩-侏罗纪分子比例小于5%，这些组合特征显示，喷泥粘土主要来源于地下千层的新近系地层，少量泥沙可能与油气同源，来自于较深埋藏的白垩-侏罗纪地层。