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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.

对四国三波川变质带（绿泥石带）、侏罗纪秩父带和白垩纪四万十带的（变）砂岩和（变）泥岩进行了地球化学和岩石学研究，以寻找三波川变质岩的非变质等效物。得到以下结论： 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。2．四万十带白垩系砂岩富含火山岩碎片，土伦期-康尼亚期岩石学和地球化学特征发生变化，可分为较老的KSI（I'）单元和较年轻的KSII（II'）单元。此分类适用于从九州到赤石群岛。3．三波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，三八川变质岩大部分属于白垩系四万十超群的深逆冲相。4．根据岩相和地球化学推测，以变砂岩为主的大步危组为坎帕期Hiwasa组及其等效的深逆冲相。5． Asemi地区的Beshi单元按化学特征可分为南北两部分，其中变砂岩和变泥岩的化学性质分别与北四万十带的KSII和KSI单元相似。 6．秩父带北缘、四国最西端的变质单元可以部分与Togano单元相关，其余与白垩纪四万十带的KSI/I'单元相关。