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喜马拉雅地体是55±10Ma以来印度陆块与欧亚大陆碰撞而形成的增生地体,位于其中的高喜马拉雅与特提斯-喜马拉雅构造单元的变质基底主要由角闪岩相的富铝变质沉积岩和花岗质片麻岩组成。对两类岩石中锆石的SHRIMPU-Pb测年结果表明,除了记录了20Ma以来的构造事件年龄外,主要保存了529-457Ma的变形和变质事件记录,另外还保存了更早期(>835Ma)的年龄信息。根据20Ma以来崛起的喜马拉雅挤出岩片中包含早期强烈褶皱和向南的斜向逆冲构造以及伴随的角闪岩相变质作用记录,结合岩石测年所获得的大量泛非-早古生代年龄和奥陶纪底砾岩的发现,说明曾位于南半球印度陆块北部的变质基底岩石经历过泛非-早古生代造山事件,同位素年代学数据表明:(1)原始喜马拉雅山是泛非-早古生代造山事件的产物;(2)印度陆块早-中元古代变质基底的再活化在原始喜马拉雅山形成中起重要的作用;(3)现在的喜马拉雅山是在泛非-早古生代造山事件基础上再造山的结果。
The Himalayan terrain is a hyperplastic body formed by the collision between Indian landmass and Eurasia since 55 ± 10Ma. The metamorphic basement in the high Himalayan and Tethyan-Himalayan tectonic units located in this area is mainly composed of amphibolite-rich Al-rich metasedimentary rocks And granitic gneiss. The results of SHRIMPU-Pb dating of zircons from two types of rocks show that in addition to recording the age of tectonic events since 20Ma, major deformation and metamorphic events of 529-457Ma have been recorded, as well as earlier (> 835Ma) Age information. According to records of the rising Himalayan extruded rock since 20Ma, there are records of early strong folds and southward thrust structures and accompanying amphibolite facies metamorphism. Combined with the large number of Pan-African Paleozoic age and Austria Discovery of Cerambite conglomerates indicates that the metamorphic basement rocks once located in the northern Indian plate of the southern hemisphere have undergone Pan-African-Early Paleozoic orogenic dating. The isotopic chronological data show that: (1) The primitive Himalayas were derived from the Pan-African-Early Paleozoic orogenic events (2) the reactivation of the early metamorphic basement and the metamorphic basement of the Indian plate plays an important role in the formation of the primitive Himalayas; (3) the present Himalayas are reconstructed on the basis of the Pan-African-Early Paleozoic orogenic events the result of.