俯冲带脱碳和固碳作用过程

俯冲带作为联系地表和地球深部系统的纽带,不仅是将地表碳带入地球深部的主要通道,也是地表物质和地球深部物质发生交换的重要场所。俯冲作用可以将地表碳以有机碳或无机碳酸盐矿物等形式带入地球深部,再通过火山作用或去气作用返回到地表系统。俯冲带深部碳循环控制着地表碳通量变化,对于研究全球气候变化和地球宜居环境具有重要意义。本文结合前人的相关研究成果,综合探讨了俯冲带的脱碳机制及固碳作用过程。俯冲带脱碳机制主要有变质反应脱碳、流体溶解脱碳和熔融作用脱碳。从俯冲板块释放的含碳流体不一定都会迁移返回地表,有一部分含碳流体在迁移演化过程中会和围岩发生反应,形成不易迁移的其他含碳相(碳酸盐、石墨或金刚石)而重新固存在俯冲板块以及上覆地幔楔中(固碳作用),进而影响碳在不同储库中的含量变化,在计算俯冲带释放碳通量时需要考虑这一过程的影响。

Decarbonation and carbonation processes in the subduction zone

As a link between the earth''s surface and its deep interior, the subduction zone is the primary tool to bring surface carbon into the deep earth and the principal place to exchange surface and in-depth materials. Subduction can bring surface carbon into the deep earth in organic carbon or inorganic carbonate minerals and then return to the surface system through volcanism or degassing. The deep carbon cycle in the subduction zone controls the surface carbon flux, which is of great significance for studying global climate change and the earth''s habitability. This paper discusses the mechanism of carbonation and decarbonation in the subduction zone. The decarbonation mechanism includes decarbonizing metamorphic reaction, carbon dissolution, and melting decarbonizing. Carbon bearing fluids released from the subducting plate may not always migrate back to the surface. Some of them will react with the surrounding rocks (carbonation) to form other solid carbon phases (carbonate, graphite, or diamond), sequestrated in the subducting plate and overlying mantle wedge. This process will affect the carbon fluxes in different reservoirs and should be considered when the carbon flux released from the subduction zone is calculated.