Quantitative modeling unifying magmatism and metamorphism

关于含水橄榄岩和玄武岩体系相关系的最新知识使我们能够模拟俯冲带的流体生成和运移。本研究建立了这样的数值模型。结果与地质和地震观测结果进行了比较。对比表明，俯冲板块的热结构（由年龄和俯冲速度决定）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，进入地幔的水在200 km以下被排出。相比之下，由于热板块，包括脊的俯冲。沟前体系同时产生了适合于高、低p /T区域变质作用的压力-温度场，并伴有大量的花岗质岩浆活动。这一结果支持了配对变质带的概念。基于最近的收敛板块边界塑性流动数值模拟，分析了白垩纪良-三巴川变质带的变形和P-T条件。分析认为，在斜度适中（俯冲方向与海沟的夹角大于45度）的弧前楔体中存在三维角流可以解释观测到的长应变。通过分析，认为同时期的Ryoke（低*P/T*） - Sambagawa（高*P/T*）变质带是在一个单一的沟-弧前体系内由一系列事件形成的，而不是由两个不同的地体偶然合并形成的，支持了“组合变质带”的概念。结果表明，在与脊状俯冲相关的动流作用下，弧前区同时出现了高、低P/T变质条件，并产生了较大的温度梯度。

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.