Constraining the age of Liuqu Conglomerate, southern Tibet: Implications for evolution of the India–Asia collision zone

Abstract

Controversy over the depositional age and provenance of the Liuqu Conglomerate along the major structural Indus–Yarlung suture zone in South Tibet clouds our understanding of the process of the India/Asia collision. Here, we report low-temperature thermochronometric data (apatite fission track, apatite and zircon (U–Th)/He for the Liuqu Conglomerate in the Xigaze area). Our new data constrain its depositional age to latest Oligocene–Early Miocene time, indicating that rather than having formed immediately following Paleogene India–Asia collision or collision between India and an intra-oceanic arc as previously proposed, the Conglomerate was probably deposited in an intermontane basin, at a slightly later time than the Gangrinboche Group to the north. The Liuqu Conglomerate should therefore not be used as a key horizon in models constraining the early stages of India/Asia collision. Our data together with previous studies suggest that the Liuqu Conglomerate was sourced from the Xigaze forearc basin, Indus–Yarlung suture zone, as well as the Tethyan Himalaya. Furthermore, our data indicate that exhumation of the Liuqu Conglomerate commenced at ∼<10–12 Ma, suggesting significant erosion in the Indus–Yarlung suture zone attributable to incision of the Yarlung Zangbo in Mid to Late Miocene time.