Oxygen fugacity-mediated carbonate reactions with siliceous fluids in shallow subduction zones  

作　　者：Fengxia Sun Jun Hu Weibin Gui Ao Deng Penghui Sun Fahui Xiong Jin Liu 

机构地区：[1]Institute of Earthquake Forecasting,The China Earthquake Administration,Beijing 100036,China [2]Center for High Pressure Science,State Key Laboratory of Metastable Materials Science and Technology,Yanshan University,Qinhuangdao 066004,China [3]Center for High Pressure Science and Technology Advanced Research,Beijing 100193,China [4]Center for Advanced Research on the Mantle(CARMA),Key Laboratory of Deep-Earth Dynamics of Ministry of Land and Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China

出　　处：《Geoscience Frontiers》2025年第1期275-286,共12页地学前缘(英文版)

基　　金：supported by the National Key Research and Development Program of China(Grant No.2023YFF0804100);the United Laboratory of High-Pressure Physics and Earthquake Science(Grant No.2022HPPES01);Some experiments are supported by the Synergic Extreme Condition User Facility(SECUF).

摘　　要：Sediments are one of the main carbon sinks in subduction zones,with CaCO_(3)and SiO_(2)being the main components in sediments.Their chemical stability plays a significant role in the form of carbon in the Earth’s mantle.Here we report the reactions of CaCO_(3)with SiO_(2)in hydrated sediments at 0.8-2.0 GPa,400-500℃and redox-buffered conditions relevant to shallow subduction zones.Our results show that the reaction CaCO_(3)+SiO_(2)=CaSiO_(3)+C+O_(2)(fluid)occurs under CoCoO and IW buffered conditions to generate wollastonite(CaSiO_(3))and carbonaceous material(CM).Moreover,wollastonite is formed by the dissolution-crystallization process,which may be significantly affected by oxygen fugacity,leading to distinct crystallization habits(Yui,1966,Schott et al.,2012).Anhydrous experiments indicate that the reaction proceeds only in the presence of H2O within the pressure and temperature(P-T)range of this study.The reaction occurs more rapidly with aragonite-structured than calcite-structured CaCO_(3).Further,the experiment buffered with natural olivine at 1.0 GPa and 400℃proves that the above reaction can occur during serpentinization processes in shallow subduction zones.More importantly,nanoscale CM may be generated under relatively reducing conditions,exhibiting Raman characteristics of kerogen.These results provide new insights into how deep carbon is distributed in the Earth’s interior.

关 键 词：Subduction zone SEDIMENTS Carbonate stability FUGACITY Graphite WOLLASTONITE 

分 类 号：O64[理学—物理化学]