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现代地质 ›› 2025, Vol. 39 ›› Issue (02): 239-247.DOI: 10.19657/j.geoscience.1000-8527.2025.026

• 深部物质组成与成矿作用 • 上一篇    下一篇

中国东部大地幔楔氧化的证据和机理

李欣懿1(), 董栩含1, 黄慧1(), 邓阳凡2, 王水炯1()   

  1. 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
  • 出版日期:2025-04-10 发布日期:2025-05-08
  • 通信作者: 王水炯,男,教授,1986年出生,地球化学专业,主要从事金属同位素地球化学研究工作。Email: wsj@cugb.edu.cn
    黄 慧,女,副教授,1986年出生,地球化学专业,主要从事同位素地球化学研究工作。Email: huihuang@cugb.edu.cn
  • 作者简介:李欣懿,女,硕士研究生,1999年出生,资源与环境专业,主要从事中国东部大地幔楔氧化研究工作。Email: 1395669423@qq.com
  • 基金资助:
    科技部研究重大计划项目(2022YFF0801004);科技部研究重大计划项目(2019YFA0708404)

The Oxidation of the Big Mantle Wedge Beneath Eastern China

LI Xinyi1(), DONG Xuhan1, HUANG Hui1(), DENG Yangfan2, WANG Shuijiong1()   

  1. 1. Institute of Earth Sciences, China University of Geosciences(Beijing), Beijing 100083, China
    2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China
  • Published:2025-04-10 Online:2025-05-08

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Fe3+/∑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Fe3+/∑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。

关键词: 大地幔楔, 板内玄武岩, 深部碳循环, 氧化

Abstract:

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 Fe3+/∑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 Fe3+/∑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.

Key words: big mantle wedge, intraplate basalt, deep carbon cycle, oxidation

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