中国东部大地幔楔氧化的证据和机理  

The Oxidation of the Big Mantle Wedge Beneath Eastern China

作　　者：李欣懿 董栩含 黄慧 邓阳凡[2] 王水炯 LI Xinyi;DONG Xuhan;HUANG Hui;DENG Yangfan;WANG Shuijiong(Institute of Earth Sciences,China University of Geosciences(Beijing),Beijing 100083,China;Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou,Guangdong 510640,China)

机构地区：[1]中国地质大学(北京)科学研究院,北京100083 [2]中国科学院广州地球化学研究所,广东广州510640

出　　处：《现代地质》2025年第2期239-247,共9页Geoscience

基　　金：科技部研究重大计划项目(2022YFF0801004,2019YFA0708404)。

摘　　要：中国东部是大地幔楔概念的提出和命名地,也是研究最为深入的区域。大地幔楔构造背景下的挥发份循环对深部地幔的氧化还原状态具有重要影响。本文回顾了前人对中国东部新生代玄武岩以及携带的地幔包体的地球化学研究,通过金属同位素、橄榄石V的氧逸度计、全岩Fe^(3+)/∑Fe表明新生代玄武岩高度氧化,其氧逸度显著高于以橄榄岩包体为代表的大地幔楔岩石圈地幔。据此,提出中国东部大地幔楔经历过一次或多次氧化事件,其氧化机制和深部碳循环密切相关。西太平洋板块俯冲携带的大量再循环碳酸盐在深部地幔发生铁-碳氧化还原反应,形成的金刚石堆积在地幔过渡带使得相应的熔体具有高的Fe^(3+)/∑Fe,形成高度氧化地幔端元(HOME),这一端元可能是深部贵金属与硫化物运移的重要介质。The Big Mantle Wedge(BMW),since first proposed in eastern China,has been extensively studied.The deep volatile cycling in the BMW system has a great impact on the redox state of the mantle.Here,we review geochemical data of the Cenozoic intraplate basalts and enclosed mantle xenoliths from eastern China,and find that the intraplate basalts are highly oxidized,with their oxygen fugacity higher than the lithospheric mantle as represented by the mantle xenoliths,based on metal stable isotope geochemistry,V-in-olivine oxybarometry,and bulk rock Fe~(3+)/∑Fe.Therefore,we propose that the BMW has experienced one or multiple oxidation events,whose trigger mechanism is closely linked to the deep carbon cycle.The subduction of western Pacific slab has delivered a large amount of sedimentary carbonates into the deep mantle,facilitating carbon-iron redox reaction in the mantle transition zone.The diamond produced during the carbon-iron redox reaction in mantle transition zone due to its high density,making the resulting melts highly enriched in Fe~(3+)/∑Fe,and the forming the highly oxidized mantle endmember(HOME),likely serving as a crucial medium for the transportation of precious metals and sulfides in the deep mantle.

关 键 词：大地幔楔 板内玄武岩 深部碳循环 氧化 

分 类 号：P588.1[天文地球—岩石学] P534.6[天文地球—地质学]