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Geochemistry of Autoliths within Granitoids

花岗岩内自生石的地球化学

基本信息

批准号：
63540655
负责人：
YAMAMOTO Masahiko
金额：
$ 1.22万
依托单位：
Kagoshima 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：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63540655/
关键词：
Granitoids Autoliths Xenoliths Mafic minerals Plagioclase feldspars オートリス

项目摘要

Modes of occurrence, mineralogy, petrology and geochemistry of dark inclusions and their rock-forming minerals were investigated within representative granitic bodies in the Outer Zone of Southwest Japan and in the Southern Kitakami Mountain lands of Northeast Japan.Dark inclusions within the S-type granitoids in the southern belt of the Outer Zone consist mainly of large amounts of sedimentary xenoliths and less autoliths with porphyritic textures ; and those within the I-type granitoids in the northern belt of common sedimentary xenoliths and autoliths with slightly porphyritic textures. Dark inclusions within the I-type granitoids of the Southern Kitakami Mountain lands consist mainly of autoliths with granular textures and less igneous and sedimentary xenoliths.Autoliths from granitoids in the Outer Zone are mainly composed of medium- to fine-grained quartz gabbroic and granodioritic rocks. The rocks are mineralogically rich in biotite and plagioclase. Autoliths from granitoids in the Southern Kitakami Mountain lands are mainly composed of coarse- to medium-grained gabbroic and quartz dioritic rocks. The rocks are mineralogically rich in hornblende and plagioclase.Autoliths are generally more basic in composition than their host granitoids, but the compositional variation ranging from autoliths to their host granitoids shows a regular trend for the individual granitic body.Mafic minerals such as biotites, amphiboles and clinopyroxenes from autoliths are generally similar in composition to those from their host granitoids. Plagioclase feldspars from some autoliths are basic in composition than those from their host granitoids. It is suggested that a genetical history is remained in zonal structures and chemical compositions of amphiboles and plagioclase feldspars from autoliths in a granitic body.

对日本西南部外带和东北部北上南部山地典型花岗岩类中的暗色包裹体及其造岩矿物的产状、矿物学、岩石学和地球化学特征进行了研究，发现外带南部带S型花岗岩类中的暗色包裹体主要由大量的沉积捕虏体和少量的斑状结构的自岩组成;北方带I型花岗岩类中常见的沉积捕虏体和少量斑状结构的自岩。北上山地南部I型花岗岩类中的暗色包裹体主要由具有粒状结构的自生岩和少量的火成岩和沉积岩捕虏体组成，外带花岗岩类中的自生岩主要由中-细粒石英辉长岩和花岗闪长岩组成。岩石矿物学上富含黑云母和斜长石。北上南部山地花岗岩类中的自岩主要由粗-中粒辉长质和石英闪长质岩石组成。岩石矿物学上富含角闪岩和斜长石。自成岩的成分一般比其寄主花岗岩类更基性，但从自成岩到其寄主花岗岩类的成分变化显示出单个花岗岩体的规律性趋势。自成岩中的镁铁质矿物如黑云母、角闪石和单斜辉石的成分一般与其寄主花岗岩类的成分相似。某些同源岩中的斜长石类晶石的成分比寄主花岗岩中的斜长石类晶石的成分更基本。认为花岗岩体中自岩形成的角闪石和斜长角闪石的环带结构和化学成分仍保留着一个成因历史。