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Basic studies on the interaction between fluids and rocks in the deep crust

地壳深部流体与岩石相互作用的基础研究

基本信息

批准号：
10304042
负责人：
HIROI Yoshikuni
金额：
$ 24.19万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10304042/
关键词：
Fluid phase High-grade metamorphics High-P and high-T Partial melting Uplift processes Hydration reactions Carbonation reactions Borosilicate minerals 高度変性岩類マグマ

项目摘要

Sample collection, field observation, petrography, and chemical analysis of rocks as well as high-pressure and high-temperature experiments of mineral synthesis and partial melting of rocks have been performed. Sample collection was carried out in the Hidaka, Abukuma and Ryoke metamorphic belts and also in the Omine Mountains. Overseas study samples are from Sri Lanka, South Africa and China. It has been revealed that the rocks have experienced variable local retrograde reactions with fluids of different compositions. Khondalite from Sri Lanka, in particular, shows evidence indicative of the presence of fluid rich in a component other than H2O and CO2. It is also unraveled that some high-grade metamorphic rocks suffered partial melting at the peak of metamorphism. Some structural and textural features of the Chinese ultra high-pressure metamorphic rocks suggest that partial melting was a significant process for the high-density rocks to uplift after the subduction down to c. 100 km in depth. The study of Omine granitic rocks was successful in observing the euhedral internal growth structures in anhedral quartz grains as the SEM CL images, which may be useful in getting new insights into the crystallization processes of granitic magmas. A paper reporting the origin of new borosilicate mineral "ominelite" and the new geochemical behaviors of boron is being in preparation. High-pressure and high-temperature experimental studies of high-grade metamorphic rocks with additional water have shown that partial melting occurs locally at the grain boundaries between some specified minerals as a kind of eutectic reactions at relatively low temperatures. With increasing temperatures compositions of partial melts become highly variable as the results of partial melting taking place more extensively at many places in the rocks.

进行了岩石的样品采集、野外观察、岩相学、化学分析以及矿物合成和岩石部分熔融的高压高温实验。在日高、阿武熊和Ryoke变质带以及大峰山脉进行了样品采集。海外研究样本来自斯里兰卡、南非和中国。结果表明，岩石与不同成分的流体发生了不同的局部退变质反应。特别是来自斯里兰卡的孔兹岩，显示出证据表明存在富含H2O和CO2以外组分的流体。一些高级变质岩在变质作用高峰期发生了部分熔融。中国超高压变质岩的一些构造和结构特征表明，部分熔融是俯冲至c.深度100公里。通过对Omine花岗质岩石的研究，成功地观察到了石英颗粒内自形生长结构的SEM CL图像，这可能对花岗质岩浆结晶过程有新的认识。报道新的硼硅酸盐矿物“矿物石”的成因和硼的新的地球化学行为的论文正在准备中。高压高温实验研究表明，在较低的温度下，某些矿物的晶界局部发生部分熔融，这是一种共晶反应。随着温度的升高，部分熔融的成分变得高度可变，因为部分熔融在岩石的许多地方发生得更广泛。