藏南新生代火山-地热区温室气体的释放通量与成因——以谷露-亚东裂谷为例

发布时间：2018-03-22 11:24

本文选题：CO释放通量　切入点：火山-地热区　出处：《岩石学报》2017年01期 　论文类型：期刊论文

【摘要】：印度-亚洲大陆俯冲带是地球深部碳循环的重要场所,在全球气候变化研究中占有至关重要的地位。谷露-亚东裂谷是青藏高原南部规模最大、延伸最长的近NS向拉张性裂谷,裂谷内出露新生代火山岩和多处大规模地热区,正在向大气圈释放巨量的温室气体。利用密闭气室法测量并计算得出的谷露和羊应火山-地热区的土壤微渗漏CO_2的平均释放通量分别为436.8g·m~(-2)·day~(-1)和99.0g·m~(-2)·day~(-1),接近具有潜在喷发危险的美国黄石公园火山-地热区(410g·m~(-2)·day~(-1))和加利福尼亚州Mammoth Mountain火山区(107.9g·m~(-2)·day~(-1))的CO_2平均释放通量,表明谷露-亚东裂谷的深部地热流体活动异常强烈。此外,在野外考察的基础上,通过实验室测试和理论计算估算了谷露-亚东裂谷每年以土壤微渗漏的形式向当今大气圈释放的CO_2总量约为1.76×107t,与西特提斯俯冲带前缘的意大利Apennine火山区CO_2的释放总量(1.32×10~7t·a~(-1))属于同一个数量级。因此,印度-亚洲大陆俯冲带是全球地质碳脱气的重要场所。气体地球化学特征显示,谷露-亚东裂谷内火山-地热气体的He同位素比值(0.10~0.29RA,RA为大气3He/4He比值)和δ~(13)CCO_2值(-7.20‰~-0.78‰)在空间分布上表现为,从南至北呈逐渐递增的变化特征,显示裂谷内火山-地热区气体在南北方向上可能具有不同的动力学成因机制。具体来讲,δ~(13)CCO_2值自南向北递增的趋势,可能与裂谷南北方向地层岩性存在差异有关;裂谷内火山-地热气体的He同位素比值高于0.1RA,揭示"重要的地幔组分",同时裂谷内地幔来源的流体组分从南向北逐渐递增的趋势表明,印度大陆岩石圈的向北俯冲作用是导致谷露-亚东裂谷内剧烈的水热活动和大规模温室气体释放最终的动力来源和成因机制。
[Abstract]:India - Asia continent subduction zone is an important place for the earth deep carbon cycle, plays an important role in the study of global climate change. Ya Dong Gulu rift is the size of the southern Tibetan Plateau, nearly NS of the longest extension to the extensional rift, outcropping Cenozoic volcano rock and many large-scale geothermal area inside Valley, is the release of greenhouse gases to the atmosphere. A huge amount of using closed chamber method to measure and calculate the Gulu and sheep should average flux of volcano geothermal zone soil microleakage of CO_2 were 436.8g m~ (-2) - day~ (-1) and 99.0g m~ (-2) - day~ (-1), close to the Yellowstone National Park volcano geothermal region has a potential danger of eruption (410g - m~ (-2) - day~ (-1)) and the California Mammoth Mountain volcano area (107.9g - m~ (-2) - day~ (-1) CO_2) the average flux shows that Gulu - deep geothermal fluid Ya Dong the same rift Very strong. In addition, based on the field investigation, laboratory test and theoretical calculation of the estimated amount of CO_2 - Ya Dong Gulu rift to the release of the annual atmosphere by soil micro leakage in the form of about 1.76 * 107t, the total release of front and Tethys subduction zone of Italy SETRA Apennine CO_2 (the 1.32 mountain fire * 10~7t a~ (-1)) belong to the same order of magnitude. Therefore, India - Asia continent subduction zone is an important place for global carbon degassing. According to geological geochemical characteristics of gases, Gulu Geothermal Gas - volcano - Ya Dong rift within the He isotope ratios (0.10~0.29RA, RA for atmospheric 3He/4He ratio) and delta. (13) CCO_2 value (-7.20% ~-0.78%) manifested in the spatial distribution, variation is gradually increasing from south to north, display volcano geothermal region gas in the rift may have different genetic dynamics mechanism in the north-south direction. Specifically, 8 ~ (1 3) the CCO_2 value increasing trend from south to north, the differences may be related to the Rift Valley north-south direction of stratum and lithology; He isotope ratios of volcano geothermal gases within the rift is higher than 0.1RA, reveal "an important component of the mantle, and the mantle derived fluid group rift points increases gradually from the South to the north of India, the trend shows that the lithosphere of the northward subduction to Gulu hydrothermal activity in the Ya Dong Valley and large-scale greenhouse gas release power source end and formation mechanism.

【作者单位】：中国科学院地质与地球物理研究所新生代地质与环境重点实验室;中国科学院地质与地球物理研究所油气资源研究重点实验室;
【基金】：中国科学院战略性先导科技专项(B类)(XDB03010600) 国家自然科学基金项目(41602341、41572321)联合资助
【分类号】：P317;P593;P314

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