Petrology of the Kamste ophiolite melange from east Junggar, Xinjiang, NW China

东准噶尔卡姆斯特蛇绿岩剖面由玄武岩、变辉长岩、辉石岩、蛇纹石片岩、硅质岩和火山碎屑岩等组成。辉石不发育出溶结构,说明地幔岩侵位过程相对缓慢(从上地幔到下地壳迁移过程中没有发生突然抬升或者 PT 条件的巨大改变)。辉石岩中存在三类角闪石:具有出溶结构的角闪石(Amp Ⅰ,镁绿钙闪石),与 Amp Ⅰ共生的均匀角闪石(Amp Ⅱ,镁质普通角闪石),以及交代单斜辉石边部的角闪石(Amp Ⅲ,钙镁闪石质普通角闪石)。基于对辉石岩和变辉长岩中角闪石的化学组成及其结构的仔细研究,获得该蛇绿岩侵位的基本演化特征如下:地幔岩在中下地壳环境被快速抬升,导致辉石岩中的角闪石分解而形成铬磁铁矿出溶结构,当蛇绿岩侵位...A newly discovered ophiolite outcrop in Kamste region, locating in the west part of the Kelameili ophiolite belt in east Junggar, consists of basalt, metagabbro, pyroxenite, serpentite schists, siltstone, and volcanic breccia. No exsolution texture occurs in pyroxene in the pyroxenite samples, which implies that the mantle rocks gradually exhumated at least in the upper mantle. Three kinds of amphiboles were identified in pyroxenite: amphibole with exsolution of Cr-magnetite lamellae (Amp I, Mg-Hastingsite), homogeneous amphibole coexisting with Amp I (Amp II, Mg-Hastingsite hornblende), and amphibole replaced clinopyroxene margins (Amp III, Tschmakite Hornblende). Based on the characteristics of the studied amphibole, we suggest that the mantle rocks were elevated to shallow levels (probably at the lower crust), which caused the decomposition of amphibole and formed the exsolution texture. When the ophiolite melange was elevated to the middle crust level, these rocks undergone retrograde metamorphism at amphibolite phase. Afterwards, these rocks have undergone retrograde metamorphism at greenschist phase when they reached the shallow level of the continental crust.SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)0071603-16102