Quantitative modeling unifying magmatism and metamorphism

统一岩浆作用和变质作用的定量模型

• 批准号: 11440159
• 负责人: IWAMORI Hikaru
• 金额: $ 9.54万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440159/
• 关键词: subduction zone; magmatism; metamorphism; numerical modeling; melting; metamorphic belt; seismic structure; 変形; 水; マグマ; コンピュータシミュレーション; 溶融; 地震波速度構造; 高圧変成帯

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.

有关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中流体的生成和迁移。这种数值模型就是在本研究中发展起来的。计算结果与地质和地震观测结果进行了对比。这些对比表明，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了俯冲带中水流体和熔体的分布，在世界上大多数俯冲带中，被俯冲到地幔中的水是在200公里以下的浅层排出的。沟前系统同时产生了既适合高P/T区域变质作用又适合低P/T区域变质作用的压力-温度场，并伴随着大量的花岗岩岩浆作用。在近期收敛板块边界塑性流动数值模拟的基础上，分析了白垩纪Ryoke-Sambagawa变质带的变形和温压条件。分析表明，弧前楔形体中的三维角流与中等倾角(俯冲方向与海沟之间的夹角大于45度)可以解释观察到的长形应变。根据分析，认为同生的Ryoke(低P/T*)-Sambagawa(高P/T*)变质带是由一系列事件在单一的地体-弧前系统内形成的，而不是两个不同的地体意外地合并而形成的，支持了“配对变质带”的概念。在弧前区，伴随着与山脊俯冲相关的动力流动，同时实现了约束的低P/T*变质条件，那里产生了大的温度梯度。

项目成果

D.Zhao, K.Asamori, H.Iwamori: "Seismic structure and magmatism of the young Kyushu subduction zone"Geophys. Res. Lett.. 27. 2057-2060 (2000)

D.Zhao，K.Asamori，H.Iwamori：“年轻九州俯冲带的地震结构和岩浆作用”地球物理学。

Okamoto A, Toriumi M: "Application of differential thermodynamics (Gibbs' method) to amphibole zonings in the metabasic system"Contrib. Mineral. Petrol. 141/3. 268-286 (2001)

Okamoto A、Toriumi M：“微分热力学（吉布斯方法）在变基础系统角闪石分区中的应用”Contrib。

H.Iwamori: "Transportation of H2O and melting beneath the Japan arcs"Bull. Earthqueake Res. Inst.. (in press). (2001)

H.Iwamori：“水的输送和日本弧线下方的熔化”公牛。

Zhao,Asamori & IWAMORI: "Seismic structure and magmatism of the young Kyushu subduction zone"Geophys.Res.Lett.. 27・14. 2057-2060 (2000)

赵朝森＆岩森：“年轻九州俯冲带的地震结构和岩浆作用”Geophys.Res.Lett.27・14（2000）

H.Iwamori: "Thermal effects of ridge subduction and its implicatins for the origin of granitic batholith and paired metamorphic belts"Earth Planet. Sci. Lett.. 181. 131-144 (2000)

H.Iwamori：“山脊俯冲的热效应及其对花岗岩岩基和成对变质带起源的影响”地球行星。