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Generation and reorganization of Oman oceanic crust-mantle

阿曼大洋壳幔的生成与重组

基本信息

批准号：
11691121
负责人：
ARAI Shoji
金额：
$ 12.8万
依托单位：
kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11691121/
关键词：
OPHIOLITE OMAN OCEANIC RIDGE UPPER MANTLE CRUST HYDROTHEMAL ALTERATION METAMOR PHIC SOLE 島弧

项目摘要

1. We recognized a wide petrographical variation of peridotite, its deformational history, cystallographical change of minerals and origin of mylonites within the upper mantle section of the northern Oman ophiolite. High-PGE chromitite was also discovered.2. We classified the late-intrusive rocks into three types in terms of petrography. Komatititic extrusives were found associated with picrite basalt, a quench phase of the late intrusives.3. The segmetation structure of a mid-ocean ridge was estimated by the strutural change of gabbroic layers. Noritic gabbro intruding around the derivative magma chmabers around the segment center impose contact metamorphism of up to granulite facies on surrounding sheeted dike complex. The structure and evolutional history of the roof zone of magma chambers were clarified.4. The upper lavas can be classified into three groups by high-accuracy chemical analysis of their Cpx phenocrysts, and the genesis was estimated for individual groups. Boninite was newly found. Preliminary data on the Salahi volcanics that erupted at the obuduction stage were presented.5. Hysrothermal metal mineralization was geologically and geochemically examined to understand its genesis. Reaction between aqueous fluid and chlorite in meta-basalts is of vital importance for their characteristics of Zn and Ni contents. The water/rock ratio in the hydrothermal fluid formation is around 20, that is far higher than the calculated values, 2 to 4.6. The thermal structure of the ocean-floor metamorphism was examined in basalt to dolerite to confirm a temprature increase downward.7. The shear sense on the metamorphic sole is NE-SW and the hanging side was confirmed to have moved toward SW.The basic amphibolite of the sole demonstrates variable flow textures within several tens of meters from the contact with overlying ultramafic rocks.

1.在阿曼北部蛇绿岩上地幔中发现了广泛的橄榄岩岩石学变化、变形历史、矿物的囊体变化和糜棱岩的成因。还发现了高PGE铬铁矿。根据岩相学将晚侵入岩划分为三种类型。发现了与苦味玄武岩共生的科马提质挤出物，该玄武岩是晚期侵入岩的急冷相。根据辉长岩层的结构变化，估算了大洋中脊的分段结构。围绕岩段中心衍生岩浆岩侵入的辉长岩，对周围席状岩墙杂岩施加了高达麻粒岩相的接触变质作用。阐明了岩浆房顶板带的构造和演化史。通过对上部熔岩的CPX斑晶进行高精度的化学分析，可将其划分为三个组，并对各个组的成因进行了估计。玻安岩是新发现的。提供了关于在浮油阶段喷发的萨拉希火山的初步数据。对热液金属矿化进行了地质和地球化学研究，以了解其成因。变质玄武岩中的绿泥石具有锌、镍的特征，水中流体与绿泥石的反应是至关重要的。热液建造中的水岩比约为20，远高于计算值2~4.6。研究了玄武岩至榴辉岩中洋底变质作用的热结构，证实了洋底变质作用的升温。变质岩底剪切方向为NE-西南向，上盘向南移动，基性角闪岩在与上覆超镁铁质岩石接触数十米范围内表现出不同的流动结构。