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

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.