西藏当雄纳龙晚古生代裂谷盆地的识别及其意义

The discovery and implications of the Nalong Late Palaeozoic rift basin in Damxung, Xizang

关键词:  冈底斯  晚古生代  裂谷盆地

Key words:  Gangdise  Late Palaeozoic  rift basin

摘要:

西藏冈底斯构造带是冈瓦纳大陆北部边缘的重要组成部分,经历了特提斯演化的全过程,并在中生代发育的典型的多岛弧-盆地系统。笔者根据冈底斯构造带中部纳龙地区晚古生代发育的沉积相类型、火山岩组合以及古生物等方面的资料,首次提出当雄纳龙盆地在中二叠世栖霞期具有裂谷盆地性质,揭示出冈底斯地区在二叠纪已转化为活动大陆边缘,为研究西藏冈底斯地区弧-盆系统的形成过程及晚古生代的区域构造特征古地理格局提供了重要的资料。

Abstract:

The Gangdise structural zone in central Xizang lies in the central part of the eastern Tethyan tectonic domain, bounded to the south by the Yarlung Zangbo suture and to the north by the Bangong-Nujiang suture zone. The structural zone is believed to be a significant component of northern Gondwanaland, where the typical archipelagic arc-basin systems were developed during the Mesozoic. The recent approaches on sedimentary facies types, volcanic rock associations and biological fossils show that the zone is not a simple microcontinent, landmass or terrane, but an archipelagic collisional orogeny that is complicated in its internal architectures and recorded all the stages of the Tethyan evolution. The Nalong Late Palaeozoic rift basin in Damxung, Xizang was once a rift basin during the Qixian (Middle Permian), implying that the Gangdise region evolved from a passive continental margin to an active continental margin during the Late Palaeozoic. The discovery of the Nalong Basin is of great significance to the improvement of our knowledge of the Late Palaeozoic regional tectonic and palaeogeographic framework of the Gangdise structural zone, and of the Late Palaeozoic Tethyan evolution of northern Gondwanaland.