Long‐term exhumation history of the Gangdese magmatic arc: Implications for the evolution of the Kailas Basin, western Tibet

Abstract

Constraining the long‐term exhumation history of the Gangdese magmatic arc is critical for understanding the coupled evolution of orogenic exhumation and accumulation of basin sediments on the southern Tibetan Plateau. We present new zircon fission‐track (ZFT) data from sandstones in the Mt. Kailas area, western Tibet, to decipher the relation between source rock exhumation and sediment deposition in the basin. Two sedimentary members were recognized in the Kailas Basin which are the Eocene conglomerates in the hanging wall of the Great Counter Thrust and the Oligocene–Miocene Kailas Formation in the footwall. The Eocene conglomerates were mostly derived from the Lhasa Terrane to the north with recycling of pre‐Cenozoic sediments, containing zircons that experienced post‐magmatic cooling after the Indian–Asian collision and buried deeply later by the Oligocene–Miocene Kailas Formation. The ZFT analysis from the Kailas Formation illustrates significant cooling during the Oligocene (ca. 32 Ma) in the source region, indicating that the Gangdese magmatic arc rocks were eroded rapidly during that time. The alternate increasing and decreasing of the southernmost Gangdese magmatic arc progresses are linked to dynamic topography deflection induced by the northward subduction of the Indian Plate since the Oligocene and subsequent southward overturning of the Indian mantle slab. Basin subsidence and formation of the Kailas Formation seems also be driven by dynamic topography since the Oligocene.