Reconstruction of Cretaceous-Eocene arcs along the southern Asian margin under Neo-Tethyan subduction

Abstract

The distribution and episodic magmatism of the southern Asian continental arc since the Cretaceous remains unclear. Here, we systematically compiled zircon UPb ages and Hf isotopic data sets, including magmatic rocks exposed on surface, detrital zircons from erosion of magmatic rocks, and xenocrystal zircons entrapped by Cenozoic volcanics from deep magmatic rocks, to elucidate these questions. Magmatic flare-up at 140–110 Ma occurred from central and northern Lhasa through eastern Tengchong to Shan Scraps, which resulted from the combination of diachronous closure of Bangong-Nujiang Tethys Ocean and subduction of a consolidated Neo-Tethys Ocean from Lhasa to Shan Scraps. During late Cretaceous-Eocene times, an extended Neo-Tethyan continental arc was built on the southern Asian margin from southern Lhasa, through Tengchong-Shan Scarps to Sumatra, excluding West Burma. The continental arc shows spatiotemporal variations in magmatism across different sections. Magmatism in eastern southern Lhasa and Sumatra is dominated by juvenile crust growth with flare-ups at 105–85 Ma and 65–45 Ma. In contrast, magmatic flare-ups at 75–45 Ma and ancient crust reworking are recorded in western southern Lhasa, Tengchong, and Shan Scraps. The spatial and temporal variations in magmatic flare-ups of Neo-Tethyan continental arc are probably related to asynchronous rollback of the Neo-Tethyan slab under different sections. During late Cretaceous-early Paleocene times, the multi-stage changes of Neo-Tethyan slab dip caused asynchronous extension-compression cycles on southern Asian continental margin.