Spatial-temporal framework of the Gangdese Orogenic Belt and its evolution.

The tectonic nature and subdivision of Gangdese Orogenic Belt is always one of the hottest scientific problems related to fundamental geology of Qinghai-Tibetan Plateau.The tectonic framework,subdivision and the Late Paleozoic-Mesozoic evolutional history of Gangdese Orogenic Belt have been studied based on regional geological survey(1:250000)and our data.Our study shows that the geological context of Gangdese can be well revealed by six major tectonic units and eighteen secondary units.Based on the analysis for spatial-temporal framework of different tectonic units and related magmatic records,we suggest that the Gangdese Orogenic Belt is not a simply block or continental segment,or terrane,but likely a complex orogenic belt experienced six arc-forming accretionary to a principal axis named Long'ge'er-Nyainqentanglha at Carboniferous-Permian,Early-Middle Triassic,Late Triassic, Early-Middle Jurassic,Late Jurassic-Early Cretaceous and Late Cretaceous-Eocene,as well as related arc-continent,continent- continent collision,and ultimately finalized its profile at the late Cenozoic.It is therefore evident that the evolutional history of Gangdese Orogenic Belt may have influenced from both the southward subduction of Bangong Co-Nujiang Tethyan Ocean crust and northward subduction of Yarlung Zangbo neo-Tethyan Ocean crust.It is emphasized that volcanic-magmatic arc formed at accretionary arc has the best potential for porphyry copper deposit in Gangdese,as revealed by Anglonggangri volcanic-magmatic arc,Dongqia Co accretionary arc and Sangri volcanic-magmatic arc,etc.