Massive abiotic methane production in eclogite during cold subduction  

作　　者：Lijuan Zhang Lifei Zhang Ming Tang Xiao Wang Renbiao Tao Cheng Xu Thomas Bader 

机构地区：[1]Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China

出　　处：《National Science Review》2023年第1期138-148,共11页国家科学评论（英文版）

基　　金：supported by the National Key Research and Development Program of China(2019YFA0708501);the National Natural Science Foundation of China(42172060 and 41702052)。

摘　　要：Methane(CH_(4))is a critical but overlooked component in the study of the deep carbon cycle.Abiotic CH_(4)produced by serpentinization of ultramafic rocks has received extensive attention,but its formation and flux in mafic rocks during subduction remain poorly understood.Here,we report massive CH_(4)-rich fluid inclusions in well-zoned garnet from eclogites in Western Tianshan,China.Petrological characteristics and carbon-hydrogen isotopic compositions confirm the abiotic origin of this CH_(4).Reconstructed P-T-fO_(2)-fluid trajectories and Deep Earth Water modeling imply that massive abiotic CH_(4)was generated during cold subduction at depths of 50-120 km,whereas CO_(2)was produced during exhumation.The massive production of abiotic CH_(4)in eclogites may result from multiple mechanisms during prograde high pressure-ultrahigh pressure metamorphism.Our flux calculation proposes that abiotic CH_(4)that has been formed in HP-UHP eclogites in cold sub duction zones may represent one of the largest,yet overlooked,sources of abiotic CH_(4)on Earth.

关 键 词：abiotic CH_(4) fluid inclusion prograde HP-UHP metamorphism CO_(2) Western Tianshan 

分 类 号：P588.1[天文地球—岩石学] P618.13[天文地球—地质学]