Petrological study on polymetamorphism of the Oki metamorphic rocks

隐岐变质岩多变质作用的岩石学研究

基本信息

批准号：
63540649
负责人：
HOSHINO Mitsuo
金额：
$ 1.09万
依托单位：
Nagoya 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 1989
项目状态：
已结题

项目摘要

Geological and petrological study was made on the Oki metamorphic rocks. Based on the data obtained from this research project, tectonic development of the Oki metamorphic massif was constructed as follows;1. Original argillaceous sediments and basaltic pyroclastics from which the Oki metamorphic rocks were derived have been formed about 2,000 Ma ago. Source rocks of the argillaceous sediments is older than 2,200 Ma in age. These early Proterozoic rocks in the Oki massif is possible to correlate with the rocks belonging to the Prechangchengian system in the Sino-Korean massif. After the sedimentation of the original rocks, at least two stages of regional metamorphism took place in the Oki massif.2. Older regional metamorphism: The age of this event is considered to be Proterozoic time. Mineral parageneses and mineral compositions indicate that the metamorphism took place under the granulite facies conditions (more than 700 ﾟC in temperature and more than 5 Kb in pressure). Extensive migmatization also occurred at the same time.3. Younger regional metamorphism: The age of this event is about 200 Ma ago. The minerals once formed under the former granulite facies conditions were retrogressively reequilibrated under the upper amphibolite facies conditions (550-650 ﾟC in temperature and 2-4 Kb in pressure) of the younger regional metamorphism. Present structural trend obtained from the minor fold axes and the mineral lineations were formed mostly at this stage.4. After that, the Oki metamorphic massif suffered mylonitization and intrusion of granitoid, and the spreading of the Japan Sea began subsequently.5. Geological and petrological correlation between the Seychelles Islands and the African Continent is also discussed in relation to this research project.

地质和岩石学研究是对OKI变质岩石进行的。根据从该研究项目中获得的数据，OKI变质块的构造开发如下构建； 1。 OKI变质岩石的原始泥质沉积物和基本的火山塑料已经形成了大约2,000 mA。泥质沉积物的源岩石年龄超过2200 mA。 OKI地块中的这些早期的properokoic岩石可以与中国 - korean massif中属于prechangechengian系统的岩石相关。原始岩石沉积后，在Oki Massif.2发生了至少两个区域变质的阶段。较旧的区域变质：这一事件的年龄被认为是元古代的时间。矿物质副磷脂和矿物质成分表明，变质发生在颗粒物设施条件下（温度下的700 c，压力超过5 kb）。同时也发生了广泛的migmatization 3。年轻的区域变质论：该事件的年龄大约是200 mA。在较年轻的区域变质中，曾经在以前的颗粒相条件下形成的矿物在温度下的闪光物相条件下（在温度下为550-650°C，在压力下为2-4 kb），对矿物质形成。从次要折叠轴和次要线条获得的当前结构趋势主要在此阶段形成。4。之后，Oki变质块遭受了花岗岩的敏化和侵入，日本海的蔓延随后开始。5。还讨论了有关该研究项目的塞舌尔群岛与非洲大陆之间的地质和岩石学相关性。