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. 我们认识到阿曼北部蛇绿岩上地幔部分橄榄岩的广泛岩石学变化、其变形历史、矿物晶体学变化和糜棱岩起源。还发现了高PGE铬铁矿。 2．我们根据岩相学将晚期侵入岩分为三类。科马提岩喷出岩与苦味岩玄武岩伴生，是晚期侵入岩的淬灭相。 3．通过辉长岩层的结构变化来估计洋中脊的分段结构。侵入段中心周围的衍生岩浆岩周围的白长岩辉长岩在周围的片状岩脉复合体上施加了麻粒岩相的接触变质作用。阐明了岩浆房顶板带的结构和演化历史。 4．通过对其 Cpx 斑晶进行高精度化学分析，可以将上部熔岩分为三组，并估计各个组的成因。博宁石是新发现的。给出了萨拉希火山仰生期喷发的初步资料。 5．对热液金属矿化进行了地质和地球化学检查，以了解其成因。水相流体与变玄武岩中绿泥石之间的反应对于其Zn和Ni含量特征至关重要。热液地层中的水岩比约为20，远高于计算值2～4.6。在玄武岩到辉绿岩中检查了海底变质作用的热结构，以证实温度下降。7．变质底部的剪切方向为NE-SW，悬挂面被证实已向SW方向移动。底部的基性角闪岩在与上覆超镁铁质岩石接触的数十米范围内表现出可变的流动纹理。