近日，中国地质大学(北京)教授邱坤峰和高世臣的课题组报道了地球深部的水循环研究，来自高压麻粒岩的综合μ-XRF、THz-TDS光谱、TG和DCS分析的见解。2023年2月24日，国际知名学术期刊《JGR地球》发表了这一成果。

本文首次采用综合显微X射线荧光光谱法(μ-XRF)、透射太赫兹时域光谱(THz-TDS)、热重分析(TG)和差示扫描量热法(DSC)对高压镁铁质麻粒岩和角闪岩的水分种类和含量进行了研究，并研究了其复水反应。他们的研究表明，石榴石、角闪石和钛铁矿含有大量的水，斜长石含有少量的分子和结构水，而石英只含有少量的结构水。石榴石释放的水和晶界外部流体，要么运移到角闪石、斜长石、钛铁矿和石英中，要么储存在地幔楔中，要么进一步俯冲到地幔深部。

该团队认为地球表面与深部地幔之间的水循环是一个不平衡过程，下地壳和地幔可能在深部储存了大量的水，并发挥容器的作用来供养和维持水循环平衡。

据了解，与俯冲作用相关的脱水作用和与挖掘作用相关的再水化作用在地球水循环中起着重要作用。水可以通过地壳俯冲输送到地幔深处，而在俯冲地壳中水在挖掘过程中的行为仍然是一个谜。

附：英文原文

Title: Water recycling in the deep Earth: Insights from integrated μ-XRF, THz-TDS spectroscopy, TG and DCS of high-pressure granulite

Author: Shan-Shan Li, Kun-Feng Qiu, David Hern, Yi-Xue Gao, M. Santosh, Hao-Chong Huang, Zhi-Yuan Zheng, Zi-Li Zhang, Shi-Chen Gao

Issue&Volume: 2023-02-24

Abstract: Subduction-related dehydration and exhumation-related rehydration play an important role in water recycling on Earth. Water can be transported to the deep mantle through crustal subduction, whereas the behaviour of water in the subducted crust during exhumation remains enigmatic. Here, we use an integrated micro X-ray fluorescence spectrometry (μ-XRF), transmission terahertz time-domain (THz-TDS), thermogravimetry (TG) and differential scanning calorimetry (DSC) approach for the first time on high-pressure mafic granulite and amphibolite to investigate the water species and contents, as well as exhumation rehydration reactions. Our study demonstrates that garnet, hornblende, and ilmenite contain considerable amounts and plagioclase contains minor amounts of water as molecular and structural species, whereas quartz contains only a minor amount of structural water. Water released from garnet and external fluids from the grain boundary will either migrate into hornblende, plagioclase, ilmenite and quartz, or stored in the mantle wedge, or further subducted into the deep mantle. We suggest that water recyclying between the Earth surface and deep mantle is an unequilibrium process, and the lower crust and mantle may store a significant amount of water in deep Earth and can function as a container to feed and maintain the water recycling balance.

DOI: 10.1029/2022JB025915

Source: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JB025915