Quantitative modeling unifying magmatism and metamorphism

最近的知识含水橄榄岩和玄武岩系统的相位关系，使我们能够模拟俯冲带中的流体生成和迁移。本研究建立了这样的数值模型。并与地质和地震观测结果进行了比较。比较表明，热结构俯冲板块的年龄和俯冲速度通过脱水反应的位置强烈地控制着俯冲带中含水流体和熔体的分布，在世界上大多数俯冲带中，俯冲到地幔中的水在200 km以下被排出。包括洋脊俯冲沟前体系同时产生了适合高、低P/T区域变质作用的压力-温度场和大量的花岗质岩浆活动。本文基于新近建立的会聚板块边界塑性流动数值模拟方法，分析了白垩纪两岳-三钵川变质带的变形和P-T条件。分析表明，一个三维角流在弧前楔与适度的俯冲（俯冲方向和沟槽之间的角度超过45度）可以解释所观察到的长应变。在此基础上，提出了同生的Ryoke（低P/T）- Sambagawa（高P/T）变质带是由一系列事件在一个单一的槽-弧前系统内形成的，而不是由两个不同的槽偶然合并而成的，支持了“平行变质带”的概念。约束低和高 *P/T* 变质条件被证明是同时实现在弧前区与动态流与脊俯冲，在那里产生了大的温度梯度。

Recent knowledge concerning the phase relationships of hydrous peridotitic and basaltic systems allows us to model fluid generation and migration in subduction zones. Such numerical model has been developed in this study. The results have been compared with geological and seismic observations. The comparisons suggest that the thermal structure (determined by age and subduction velocity) of the subducting plate strongly controls the distribution of the aqueous fluids and melts in subduction zones through the position of the dehydration reactions, and that water subducted into the mantle is expelled at shallower than 200 km in most of the subduction zones in the world.By constrast, as a consequence of the hot plate, including ridge subduction. pressure-temperature field appropriate for both high-and low-P/T regional metamorphism, together with a large amount of granitic magmatism, are produced simultaneously in the trench-foreacr system. The result supports the concept of paired metamorphic belts.Deformation and P-T conditions of the Cretaceous Ryoke-Sambagawa metamorphic belts have been analyzed based on recent numerical modeling of plastic flow at convergent plate boundaries. The analyzes suggest that a three-dimensional corner flow in the forearc wedge associated with moderate obliquity (more than 45 degrees for the angle between the subduction direction and the trench) can explain the observed prolate strain. Based on the analyzes, the contemporaneous Ryoke (low *P/T*) - Sambagawa (high-*P/T*) metamorphic belts are suggested to have been formed within a single trehch-forearc system by a series of the events, not by accidental amalgamation of two distinct terranes, supporting the concept of a 'paried metamorphic belts'. The constrasting low- and high-*P/T* metamorphic conditions are demonstrated to be simultaneously achieved in the forearc region with the dynamic flow associated with ridge subduction, where a large temperature gradient is produced.