The granitic gneisses from the Namjagbarwa Group Complex within the eastern Himalayan syntaxis,Xizang
-
摘要: 野外地质填图和研究发现,东喜马拉雅构造结高喜马拉雅结晶岩系中有古老的花岗岩侵入,并在鲁霞地区圈定了9个花岗质侵入体。古老的花岗质岩石主要侵位于南迦巴瓦岩群直白岩组中,与南迦巴瓦岩群一起经历了麻粒岩相变质作用而形成花岗质片麻岩套。岩石类型有花岗闪长质片麻岩、黑云母花岗质片麻岩、闪长质片麻岩等。岩石化学研究表明这些花岗片麻岩套具“S”型特征,可能有深部幔源物质的加入。花岗岩形成深度在2～5km之间,侵位时代为552～525 Ma,为新元古代晚期,属泛非期陆内演化阶段的产物。高喜马拉雅地区在元古宙末期形成了结晶基底。Abstract: The old granites from the Higher Himalayan crystallines within the eastern Himalayan syntaxis,Xizang are mostly emplaced into the Zhibai Formation Complex in the Namjagbarwa Group Complex and constitute the granitic gneissic suites resulted from the granulite-facies metamorphism.Nine granitic intrusives may be delineated in the Luxia region,and the rock types include granodioritic gneiss,biotite granitic gneiss and dioritic gneiss.The features of the "S" type granites indicate by chemical compositions suggests the possibility of the addition of deep-seated mantle-derived matter.These granites may be localized at the depth of 1-5 km and 552-525 Ma in age latest Neoproterozoic,representing the products generated during the Pan-African intracontinental orogenesis.The presence of the Pan-African granitic gneisses and associated amphibolite has disclosed that the amphibolite-facies metamorphism accompanied with ganitic intrusion once occurred during the latest Neoproterozoic 575.20±5.24 Ma-525 Ma.This tectonic-thermal event marked the formation of the Higher Himalayan crystalline basement,and a new cycle of tectonism in the surveyed area.
-
Keywords:
- eastern Himalayan syntaxis /
- Namjagbarwa Group Complex /
- granitic gneiss /
- Xizang
-
计量
- 文章访问数: 124
- HTML全文浏览量: 0
- PDF下载量: 81
下载:
