Hadal aragonite records venting of stagnant paleoseawater in the hydrated forearc mantle
Hadal aragonite records venting of stagnant paleoseawater in the hydrated forearc mantle
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DOI：
10.1038/s43247-021-00317-1
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发表时间：
2021-12
影响因子：
7.9
通讯作者：
R. Oyanagi;A. Okamoto;M. Satish-Kumar;M. Minami;Y. Harigane;K. Michibayashi
中科院分区：
文献类型：
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作者：
R. Oyanagi;A. Okamoto;M. Satish-Kumar;M. Minami;Y. Harigane;K. Michibayashi
海沟上的哈达尔带是一个独特的区域，由于构造侵蚀，弧前地幔岩石直接暴露在海底。地幔岩石中海水的循环诱导了深海弧前地幔内的碳酸盐沉淀，但循环的时间尺度和速率尚不清楚。本文研究了伊豆-小川海沟约6400 m水深的弧前地幔岩石中一种特殊的碳酸钙(文石)赋存状态。根据显微结构、锶碳氧同位素地球化学和放射性碳分析，我们发现该文石来源于42000多年前的海水。文石的沉淀是由幕式破裂事件触发的，这些破裂事件将聚集在10−2-10−1M S−1的流体排出，最多持续几十年。我们认为，来自最浅的弧前地幔的俯冲海水的循环影响了碳从表面到地球内部的运输。
The hadal zone at trenches is a unique region where forearc mantle rocks are directly exposed at the ocean floor owing to tectonic erosion. Circulation of seawater in the mantle rock induces carbonate precipitation within the deep-sea forearc mantle, but the timescale and rates of the circulation are unclear. Here we investigated a peculiar occurrence of calcium carbonate (aragonite) in forearc mantle rocks recovered from ~6400 m water depth in the Izu–Ogasawara Trench. On the basis of microtextures, strontium–carbon–oxygen isotope geochemistry, and radiocarbon analysis, we found that the aragonite is sourced from seawater that accumulated for more than 42,000 years. Aragonite precipitation is triggered by episodic rupture events that expel the accumulated fluids at 10−2–10−1m s−1and which continue for a few decades at most. We suggest that the recycling of subducted seawater from the shallowest forearc mantle influences carbon transport from the surface to Earth’s interior.