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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.

对四国三巴川变质带(绿泥石带)、侏罗纪赤部带和白垩纪岛曼都带的变质砂岩和变质泥岩进行了地球化学和岩石学研究，以寻找与三巴川变质岩对应的非变质岩石。得到了以下结论：1.赤赤部带早侏罗世砂岩与晚侏罗世砂岩在岩石学和地球化学上存在差异。石门托带白垩系砂岩富含火山岩碎屑，在都罗纪-科尼亚纪岩石学和地球化学特征发生了变化，可划分为较老的KSI(I‘)和较年轻的KSII(II’)两个单元。这一分类适用于从九州到赤石村。三巴川变质带中的变质砂岩和变泥岩与白垩纪Shimanto带中的砂岩和页岩具有地球化学亲缘关系。这一证据表明，桑巴加瓦变质岩大多为白垩纪Shimanto超群的深冲断相。根据岩相和地球化学特征，推测以变质砂岩为主的鄂博克单元为坎帕尼亚希瓦萨组和/或其对应的深冲断相。根据化学特征，阿西姆地区的贝石单元可划分为北部和南部，其中变质砂岩和变泥岩的化学成分分别与北部岛曼托带的KSII和KSI单元相似。赤部带北缘最西端的四国变质单元与白垩纪岛本带的Togano单元部分对应，其余与Ksi/I‘单元对应。