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The Process of formation of extremely high temperature zones in the deep crust beneath the Miocene Setouchi volcanic province

中新世濑户内火山省地壳深部极高温区的形成过程

基本信息

批准号：
05402021
负责人：
KOMATSU Masayuki
金额：
$ 18.37万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

The aim of this project is to investigate the crustal composition and structure, and the influence and nature of magmatic activity based on the research of metamorphic xenoliths enclosed in volcanic rocks and of intermediate and acidic volcanic rocks in the Miocene Setouchi volcanic province.1. Metamorphic xenoliths were collected from Nijozan (Kinki district), Amataki-yama and Amagiri-yama (Eastern Shikoku), and Kaminada dacite mass and Ishizuchi andesite formation and dikes (Western Shikoku). The xenoliths, except for those from Amagiri-yama, have been thermally metamorphosed and suffered partial melting at the wall of magma chambers which were formed in relatively shallow levels of the crust. The crust was heated to extremely high temperature, causing partial melting of crustal rocks to produce acidic igneous rocks. The original lithology of metamorphic xenoliths varies widely from mafic granulite and high grade pelitic gneisses to mafic and pelitic schists. The xenoliths from Amagiri-yama suffered varied thermal effects depending on the time they were holded in the magma, namely, on the level where they occurred. The crust is infered to consist, from shallow to deep, of Ryoke granite-gneisses, granulite facies gneisses and mylonites, Sanbagawa schists, and high temperature type gneisses.2. High temperature hornfels of Middle Miocene age have been found to occur in the Sanbagawa schists and revealed that they were formed by extremely high temperature fluid flows. The fluid flow is related to the Setouchi igneous activity, and directly derived from the magma chamber. This proves the shallow magma chamber beneath the Setouchi province.

本课题的目的是通过对中新世濑户内火山省火山岩包藏变质捕虏体和中酸性火山岩的研究，探讨地壳成分和结构、岩浆活动的影响和性质。 1．变质捕虏体采集自二条山（近畿地区）、天泷山和天桐山（四国东部）以及上田英安岩体和石锤安山岩地层和岩脉（四国西部）。除了来自天雾山的捕虏体外，其他捕虏体都在地壳相对较浅的位置形成的岩浆室壁上发生了热变质和部分熔融。地壳被加热到极高的温度，导致地壳岩石部分熔化，产生酸性火成岩。变质捕虏体的原始岩性变化很大，从镁铁质麻粒岩和高品位泥质片麻岩到镁铁质和泥质片岩。天桐山的捕虏体遭受不同的热效应，具体取决于它们在岩浆中停留的时间，即它们出现的高度。推测地壳由浅到深依次为Ryoke花岗片麻岩、麻粒岩相片麻岩、糜棱岩、三八川片岩、高温型片麻岩。2．在三波川片岩中发现了中中新世高温角岩，表明它们是由极高温流体流形成的。流体流动与濑户内火成岩活动有关，并且直接源自岩浆房。这证明了濑户内省下方存在浅层岩浆房。