关键词: 拉萨地体, 冈底斯岩浆带, 新特提斯洋, 岩石地球化学, 构造演化

Abstract: The Gangdese magmatic belt is the product of the northward subduction of the Neo-Tethys oceanic lithosphere beneath the Lhasa terrane and subsequent India-Asia collision. The Gangdese magmatic arc belongs to the typical continental magmatic belt and is the target area for studying plate accretion, crustal growth and reworking and collisional orogeny. Numerous lines of evidence indicate that the Neo-Tethys oceanic lithosphere experienced four distinct stages of evolution: the early-stage subduction (>152 Ma), late-stage subduction (100 to 65 Ma), main-collisional (55 to 40 Ma), and post-collision extentional stages (23 Ma to present). Multiple studies were carried out in the Gangdese belt and much progress has been made during past decades. However, the formation and evolution of the Neo-Tethys Ocean and magma source of igneous rocks are still debated, especially the detailed petrogenetic dynamic processes. This paper reviews the evolution history and tectonic background, and then summarizes related

scientific problems from thirteen aspects. It is shown that the Gangdese magmatic belt is a typical magmatism-tectonismmineralization-deformational metamorphism belt and experienced multi-stage evolution processes rather than a simple
continental magmatic arc aggregated in the Lhasa terrane. The review shows that (1) the Gangdese magmatic belt is a natural
laboratory for studying the evolution history of the Neo-Tethys, and provides better constraints on the styles of the subducting
slab. (2) The different-stage granitoid stocks and batholiths might be formed by multiple additions and incremental assembly of
magmas over a span of millions of years or even longer. Therefore, we should use a mush model to reconstruct petrogenesis and
petrogenetic secnarios of granitoid rocks in detail. (3) The mantle nature of the Gangdese region shows complicated features that
are characterized by geochemical heterogeneity along the arc strike direction. (4) The reversed isotopes exist in the Gangdese belt, probably indicating an ancient nucleus. (5) The Gangdese belt is tilting and has different crustal compositions that are characterized by lower crustal compositions in the eastern segment and middle-upper crustal compositions in the middle-western segment. Crustal tilting of the Gangdese region suggests a differential and imbalanced exhumation process. (6) At present, numerous studies are focused on igneous rocks with methods mainly including radioactive Sr-Nd-Hf isotopes, whereas non-traditional stable isotopes (Mg-O-Li-B-Mo) are rarely reported. In addition, research topics are mainly associated with petrogenesis and geochronology, but few studies focus on the magma emplacement and post-magmatic deformation and uplifting-denudation processes. (7) Research in structural geology of the area is few and usually tectonic evolution is inferred from magmatic evolution in the Gangdese belt, southern Tibet. Finally, we also provide future prospects based on the current research status of the Gangdese magmatic belt in southern Tibet.

Key words: Lhasa terrane, Gangdese magmatic belt, Neo-Tethys Ocean, Petro-geochemistry, tectonic evolution