Recycled calcium carbonate is an efficient oxidation agent under deep upper mantle conditions
Recycled calcium carbonate is an efficient oxidation agent under deep upper mantle conditions
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DOI：
10.1038/s43247-021-00116-8
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发表时间：
2021-02
影响因子：
7.9
通讯作者：
Renbiao Tao;Y. Fei
中科院分区：
文献类型：
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作者：
Renbiao Tao;Y. Fei
金刚石石榴石包裹体和地幔柱熔体中高铁含量的观测表明，地幔中高铁的分布具有高度的不均匀性。通过俯冲作用从地球表面回收碳酸盐等氧化物质可以解释观察到的变化。在这里，我们提出了高压高温多砧实验，以确定钙，镁，或铁碳酸盐和含亚铁硅酸盐矿物（石榴石或铁橄榄石）之间的氧化还原反应在条件下的俯冲带与中间热结构的代表。我们表明，石榴石和铁橄榄石可以氧化为富铁石榴石伴随着减少碳酸钙形成石墨。合成石榴石中三价铁的含量随压力的增加而增加，并与石榴石中的Ca含量有关。我们认为，再循环沉积碳酸钙可以通过有效地增加上地幔深部的三价铁含量来影响地幔氧化态的演化。
Observations of high ferric iron content in diamond garnet inclusions and mantle plume melts suggest a highly heterogeneous distribution of ferric iron in the mantle. Recycling of oxidized materials such as carbonates from Earth’s surface by subduction could explain the observed variations. Here we present high-pressure high-temperature multi-anvil experiments to determine the redox reactions between calcium-, magnesium-, or iron-carbonate and ferrous iron-bearing silicate mineral (garnet or fayalite) at conditions representative of subduction zones with intermediate thermal structures. We show that both garnet and fayalite can be oxidized to ferric iron-rich garnets accompanied by reduction of calcium carbonate to form graphite. The ferric iron content in the synthetic garnets increases with increasing pressure, and is correlated with the Ca content in the garnets. We suggest that recycled sedimentary calcium carbonate could influence the evolution of the mantle oxidation state by efficiently increasing the ferric iron content in the deep upper mantle.