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Tectonics of the Outer Zone of Southwest Japan as inferred from microtextur of its constituen rock

从其构成岩石的微观结构推断日本西南外带的构造

基本信息

批准号：
04640705
负责人：
HARA Ikuo
金额：
$ 1.54万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640705/
关键词：
Sambagawa megaunit Chichibu megaunit metamorphic rocks of high-pressure type Subduction zone tectonic erosion underplating P-T-t-D path folding mechanism ナップ運動像フレクシュラル・スリップシース褶曲石英ファブリック放射年代高圧変成岩の上昇機構 two way Streets mod

项目摘要

The Outer Zone of Southwest Japan consists of the four megaunits.Chichibu megaunit II,Sambagawa megaunit.Chicibu megaunit I and Shimant megaunit in descending order of structural level.On the basis of microtextures of the Sambagawa megaunit rocks, especially Saruta nappe (I+II) schists and Fuyunose nappe schists, it has been clarified that in subduction channel sediment subduction occurs a accompanying tectonic crosion and mixing of the hanging wall rocks.From analysis of microtextures and P-T-t-D path of the Sogauchi nappe schists, it has been pointed out that they consist of three subnappes, ST subnappe, KAT subnappe and NOM subnappe in descending oreder of structural level, which are succesively underplated with downward decrease of pressure and temperature, and that the underplating processes is ascribed to upflow of subducted sehiments from control point of subduction channel.From relationship in microtextures and P-T-t-D path between the Sogauchi nappe schists and the Sakamoto-Niyodo nappe schists (Chichibu megaunit I), it has benn concluded that the Sambagawa megaunit schists as metamorphic rocks of high-pressure type were exhumed along the mechanial boundary of the Cretaceous convergence zone.The folding of the Sambagawa megaunit schists during the last phase of deformation shows a transition from flexural-flow type to flexural-slip type.

日本西南外带由秩父巨单元II、三钵川巨单元、秩父巨单元I和Shimant巨单元组成，根据三钵川巨单元岩石，特别是猿田推覆（I+II）片岩和冬之濑推覆片岩的显微结构，阐明了在俯冲通道中，沉积物的俯冲伴随着构造的碰撞和上盘岩石的混合，根据总沟内推覆片岩的显微结构和P-T-t-D轨迹，指出总沟内推覆片岩由ST、KAT和NOM三个亚推覆体组成，在构造层次上由低到高依次为ST亚推覆体、KAT亚推覆体和NOM亚推覆体，它们呈俯冲式底侵，压力和温度向下降低，底侵作用是俯冲沉积物从俯冲通道控制点上涌的结果通过对Sogauchi推覆片岩与Sakamoto-Niyodo推覆片岩（秩父巨单元I）的P-T-t-D轨迹的对比，认为Sambagawa巨单元片岩作为高压型变质岩，是沿着白垩纪汇聚带的机械边界出露的，变形末期的褶皱表现为从挠曲流动型向挠曲滑动型的转变。