Rupture of wet mantle wedge by self-promoting carbonation
Rupture of wet mantle wedge by self-promoting carbonation
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DOI：
10.1038/s43247-021-00224-5
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发表时间：
2021-08
影响因子：
7.9
通讯作者：
A. Okamoto;R. Oyanagi;Kazuki Yoshida;M. Uno;H. Shimizu;M. Satish-Kumar
中科院分区：
文献类型：
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作者：
A. Okamoto;R. Oyanagi;Kazuki Yoshida;M. Uno;H. Shimizu;M. Satish-Kumar
每年有超过一四摩尔的碳被俯冲为碳酸盐或碳质材料。然而，人们对碳化/脱碳反应对俯冲带内地震活动的影响知之甚少。在这里，我们展示了日本 Higuchi 蛇纹岩体内碳酸盐岩脉的现场和微观结构观察，包括稳定同位素分析。我们发现碳酸盐岩脉的碳和氧同位素组成表明含碳流体源自变沉积物中的有机物质。热力学计算表明，蛇纹石的碳化伴随着固体体积减少、脱水和高镁迁移率。我们认为地幔楔的碳化以自我促进的方式间歇性地发生，并受到固体体积收缩和流体超压的控制。在我们的概念模型中，脆性破裂和碳酸盐沉淀之后是碳酸盐和含水矿物的延性流动；这或许可以解释蛇纹石化地幔楔中发生阵发性震颤和滑动的原因。
More than one teramole of carbon per year is subducted as carbonate or carbonaceous material. However, the influence of carbonation/decarbonation reactions on seismic activity within subduction zones is poorly understood. Here we present field and microstructural observations, including stable isotope analyses, of carbonate veins within the Higuchi serpentinite body, Japan. We find that the carbon and oxygen isotope compositions of carbonate veins indicate that carbonic fluids originated from organic materials in metasediments. Thermodynamic calculations reveal that carbonation of serpentinite was accompanied by a solid volume decrease, dehydration, and high magnesium mobility. We propose that carbonation of the mantle wedge occurs episodically in a self-promoting way and is controlled by a solid volume contraction and fluid overpressure. In our conceptual model, brittle fracturing and carbonate precipitation were followed by ductile flow of carbonates and hydrous minerals; this might explain the occurrence of episodic tremor and slip in the serpentinized mantle wedge.