Abstract:

The preCenozoic evolution of the Tethys and the Cenozoic uplift of the Tibetan Plateau have long been considered as two important issues of fundamental geology of this plateau. However, our knowledge on the geological context and preCenozoic history of the Tibetan Plateau remains limited so far, consequently raising uncertainties for further exploring the history of Tibetan uplift during the Cenozoic. New available geological and geochemical data of volcanic rocks indicate the coexistence of an islandarc system in the Gangdese and an extensional setting in the Himalayas during the Early to Middle Permian. Peraluminous Stype granites near Pikang (~263 Ma), the Songdo eclogite of the same metamorphic age (~262 Ma), and the regional angular unconformity between the Middle and the Upper Permian from the same geotectonic location suggest that the presentday Gangdese Retroarc Uplift Belt (GRUB) experienced a syncollisional orogeny at the latest Middle Permian (~263 Ma). UPb age dates and Hf isotopic compositions of zircons from Mesozoic magmatic rocks reveal that the GRUB and Middle Gangdese are characterized by an ancient basement of Paleoproterozoic (as old as Archean) age, whereas the Northern and Southern Gangdese are dominated by MesoNeoproterozoic and Phanerozoic juvenile crust, respectively. Available good quality age dates and zircon Hf isotopic data suggest that the northern parts of the Gangdese experienced a zonal magmatic flareup with strong input of mantlederived materials at ~110 Ma. New reliable UPb age dates of the extensive Cretaceous igneous rocks in the eastern Himalayas suggest that these rocks were emplaced at about 132 Ma, and may represent the erosional and/or deformational remnants of the newly identified ComeiBunbury large igneous province. All these new data formed a basis for discussing the tectonomagmatic and Tethyan evolution in presentday southern Tibet during the Late PaleozoicMesozoic.

Key words: Key words: Permian; Early Cretaceous; tectonomagmatism; Tethyan evolution; southern Tibet