Thermodynamic forward modeling of progressive dehydration reactions during subduction of oceanic crust under greenschist facies conditions
Thermodynamic forward modeling of progressive dehydration reactions during subduction of oceanic crust under greenschist facies conditions
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DOI：
10.1016/j.epsl.2011.01.027
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发表时间：
2011-07-01
影响因子：
5.3
通讯作者：
Toriumi, Mitsuhiro
中科院分区：
文献类型：
--
作者：
Kuwatani, Tatsu;Okamoto, Atsushi;Toriumi, Mitsuhiro
我们开发了一种基于微分热力学方法（吉布斯方法）和使用质量平衡方程的热力学正演模拟研究脱水反应的新方法。为了研究洋壳俯冲过程中连续递进的脱水反应，我们将模型应用于绿片岩衰退条件下的基性体系。通过指定P-T的变化，该模型使我们能够预测矿物学和成分的变化以及产水量的增量。对沿几种典型P-T路径俯冲的MORB（洋中脊玄武岩）整体成分岩石的计算表明，在绿片岩和（绿帘石-）角闪岩相的边界附近，脱水过程迅速进行，绿泥石在那里反应出来。在日本西南部和门多西诺角的俯冲带，脱水率峰值的计算深度与地震活动群的峰值以及低频震动和高泊松比的深度范围有很好的相关性。这一发现表明地震现象与俯冲洋壳脱水反应之间有很强的因果关系。(c) 2011 Elsevier B.V.版权所有
We developed a new approach to the study of dehydration reactions using thermodynamic forward modeling based on the differential thermodynamic approach (the Gibbs' method) and the use of mass balance equations. We applied the modeling to mafic systems under conditions of the greenschist fades in order to investigate continuous, progressive dehydration reactions during subduction of oceanic crust. By specifying the changes in P-T, the model enables us to predict changes in modal mineralogy and composition as well as the incremental amount of water produced. Calculations for rocks of MORB (mid-ocean ridge basalt) bulk composition subducting along several typical P-T paths show that dehydration proceeds rapidly near the boundary between the greenschist and (epidote-) amphibolite facies, where chlorite is reacted out. The calculated depths for peak rates of dehydration correlate well with peaks in clusters of seismic activity and the depth ranges of low-frequency tremors and high-Poisson's ratio in the subduction zones of SW Japan and Cape Mendocino. This finding indicates a strong causal linkage between seismic phenomena and dehydration reactions in subducting oceanic crust. (c) 2011 Elsevier B.V. All rights reserved.