The Ophiolites in the Outer Zone of Southwest Japan and their development mechanism

日本西南部外围地带的蛇绿岩及其发育机制

• 批准号: 59420017
• 负责人: SUZUKI Takashi
• 金额: $ 18.56万
• 依托单位: Kochi 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: 1984
• 资助国家: 日本
• 起止时间: 1984 至 1985
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-59420017/
• 关键词: X-ray fluorescence analyser; the Mikabu Ophiolite; the Kurosegawa Tectonic Zone; the Chichibu Belt; the Shimanto Belt; metabsalt; 玄武岩; チャート

The main results by this studies, mainly using the automatic X-ray fluorescence analyser(system 3080), are as follows;1. For 61 samples of cherts, siliceous mudstones, mudstones and tuffs from the Ogawa belt and the Nishiyama II belt in the Togano Group (middle - upper Jurassic) of the Chichibu Southern Belt, we analysed chemically: 11 major and 9 minor components. As a result, it became clear that the cherts of the Ogawa belt is of pelagic in origin and those of the Nishiyama II belt is of hemipelagic.2. The bulk chemical compositions and relic clinopyroxene chemistry of the most metabasalts from the Shimanto Belt in Kyushu, Shikoku and Kii Peninsula, show much closer to those of the ocean-floor basalt(the present-day abyssal tholeiite). On the other hand, the relic clinopyroxenes in the metadoleritic rocks have alkaline magma affinity. Conclusively, the fact that thetholeiitic and alkaline rocks are mixed within the mudstone-melanges as exotic bodies contiguous to each other, indicates a complicated accretion process of the Shimanto Belt.3. The serpentinites in the Kurosegawa Tectonic Zone of eastern part of Kii Peninsula show processes of development as follows;(1) this rocks were serpentinized once at about 300゜C. (2) They heated at higher temperature of about 400゜ - 500゜C and metamorphosed olivine and clinopyroxene were formed. (3) They were metamorphosed again to the serpentinized rocks during serpentinite-melange development.4. The Mikabu Ophiolites at Kichijou-san(Aichi Prefecture) are intensively sheared and broken. As a result, they consist of high P/T and high T/P metamorphic rocks and might have been mixed each other by complicated process of melange development.5. The meta-basic rocks in the sheared mudstone matrix of the Kamuikotan Ophiolite Belt consist of calc-alkaline, tholeiitic and alkaline rocks. They might be mixed by complex tectonic process.

本研究主要利用全自动X射线荧光分析仪（3080系统）进行分析，主要结果如下：1。对产自秩父南部岩带中上侏罗统户野群小川岩带和西山II岩带的61个硅质岩、硅质泥岩、泥岩和凝灰岩样品进行了化学分析：11个主要组分和9个次要组分。结果表明，小川带的硅质岩属远洋成因，西山II带的硅质岩属半远洋成因。九州、四国和纪半岛的四万十带变质玄武岩的整体化学成分和残余单斜辉石化学成分与大洋底玄武岩（即现今深海拉斑玄武岩）的成分更为接近。变质闪长质岩石中残留的单斜辉石具有碱性岩浆亲合性。总之，拉斑玄武岩和碱性岩混合在泥岩混杂岩中，作为彼此相邻的外来体，这一事实表明了四万十带复杂的增生过程。纪伊半岛东部黑濑川构造带蛇纹岩的发育过程为：（1）在300 ℃左右曾发生一次蛇纹化作用; (2)它们在约400 ° C- 500 ° C的较高温度下加热，形成变质橄榄石和单斜辉石。(3)在蛇纹岩-混杂岩的发育过程中，再次变质为蛇纹化岩.吉条山（爱知县）的三分蛇被密集地剪切和破碎。因此，它们是由高P/T和高T/P的变质岩组成，并可能在复杂的混杂岩发育过程中相互混合。龟尾潭蛇绿岩带剪切泥岩基质中的变基性岩由钙碱性岩、拉斑玄武岩和碱性岩组成。它们可能因复杂的构造作用而混合。