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

- Depositional age for the Liuqu Conglomerate is probably Early Miocene based on low-T data.
- Liuqu Conglomerate was sourced from Indus-Yarlung suture zone, Xigaze forearc basin and TH.
- Liuqu Conglomerate experienced an exhumation at ∼10-12 Ma.

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.

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