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Geochemical relationships between psammitic-pelitic rocks from the Sanbagawa Metamorphic Belt and Jurassic-Cretaceous accretionary complexes (Southern Chichibu-Nrothern Shimanto Belts)

三波川变质带砂岩-泥质岩与侏罗纪-白垩系增生杂岩（秩父南部-四万十北部带）的地球化学关系

基本信息

批准号：
09640546
负责人：
KIMINAMI Kazuo
金额：
$ 1.73万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2000
项目状态：
已结题

项目摘要

Geochemical and petrological studies (meta-)sandstones and (meta-) pelite from the Sanbagawa Metamorphic Belt (chlorite zone), Jurassic Chichibu Belt and Cretaceous Shimanto Belt in Shikoku have been performed to find the non-metamorphic equivalents of the Sanbagawa metamorphic rocks. Following conclusions are obtained.1. In the Chichibu Belt, Early Jurassic sandstones differ from Late Jurassic ones in terms of petrography and geochemistry.2. Cretaceous sandstones in the Shimanto Belt, which are rich in volcanic rock fragments, change in petrological and geochemical featrures during the Turonian-Coniacian, and Can be divided into older KSI (I') and younger KSII (II') units. This classification is applicable from Kyushu to the Akaishi Nountains.3. Metasandstones and metapelites from the Sanbagawa Metamorphic Belt have geochemical affinities with sandstones and shales in the Cretaceous Shimanto Belt. This evidence suggests that most of the sanbagawa metamorphic rocks are deeply underthrust facies of the Cretaceous Shimanto Supergroup.4. the Oboke unil mainly composed of metasandstones is presumed to be the deeply underthrust facies of the Campanian Hiwasa Formation and/or its equivarent on the basis of lithofacies and geochemistry.5. The Beshi unit of the Asemi area can be divided on the basis of chemical features into northern and southern parts of which metasandstones and metapelite are chemically similar to KSII and KSI units in the northern Shimanto Belt, respectively.6. Metamorphosed units on the northern margin of the Chichibu Belt, westernmost Shikoku, can be partly correlative to the Togano unit and the rest with KSI/I' unit in the Cretaceous Shimanto Belt.

对四国三坝川变质带、侏罗纪秩父变质带和白垩纪四万十变质带中的（Meta）砂岩和（Meta）泥质岩进行了地球化学和岩石学研究，以寻找三坝川变质岩的非变质等价物。得出以下结论：1.秩父带早侏罗世砂岩与晚侏罗世砂岩在岩石学和地球化学方面存在差异。四万十带白垩系砂岩富含火山岩碎屑，在Turonian-Coniacian期岩石学和地球化学特征发生变化，可划分为较老的KSI（I '）和较年轻的KSII（II'）单元。本分类适用于从九州到赤石川。3.三坝川变质带的变砂岩和变泥岩与白垩纪四万十带的砂岩和页岩具有地球化学亲缘关系。这一证据表明，大部分的三坝川变质岩是白垩纪四万十超群的深冲断层相。以变质砂岩为主的Oboke单元，根据岩相和地球化学特征，推测为Campanian Hiwasa组和/或其等价物的深俯冲相. Asemi地区的Beshi单元可根据化学特征分为北方和南方两部分，其中变砂岩和变岩的化学性质分别类似于北方Shimanto带的KSII和KSI单元。四国最西端秩父带北方边缘的变质单元可部分与东野变质单元对比，其余与白垩纪四万十带的KSI/I'变质单元对比。