Spatial‐Temporal Variation in Erosion Rate of Lohit Bomi‐Chayu Batholith Around Eastern Himalayan Syntaxis (SE of the Namche Barwa Massif)

AbstractMeasuring erosion rates around the Eastern Himalayan syntaxis is crucial to understanding the interaction between tectonic, climate, and landscape associated with Eastern Himalayan termini. The spatio‐temporal deformation history around the eastern syntaxis is unclear due to a lack of comprehensive thermochronological data coverage, especially from the Lohit Bomi‐Chayu (LBC) batholith. This work utilizes 2473 new detrital fission track ages of apatite and zircon grains from 14 catchments, and 17 new bedrock thermochronometric ages (eight AFT, six ZFT, and three ZHe ages) from 12 rock samples collected along rivers flowing through the LBC batholith to quantify the spatio‐temporal erosion history. Bayesian probability, Markov chain Monte Carlo algorithm, and bootstrapping were applied for the inversion of detrital cooling ages to model various erosion histories. Results indicate an increased erosion rate in the batholith at least four times from the Miocene to the present. Specifically, LBC batholith's erosion rates were lower (∼0.16 mm/yr) before the Miocene and increased (∼0.61 mm/yr) during the Early‐Middle Miocene to the present. The post‐Miocene erosion rate is similar to SE Tibet, Bhutan, and Arunachal Pradesh rates. However, it is lower than Nepal. Pre‐Miocene rates are significantly low and comparable only with that of SE Tibet. We envisage that the Early‐Middle Miocene enhanced erosion was related to the tectonic uplift along the Jiali shear zone. This surface uplift was in close concurrence with increased precipitation that might have disconnected the Yigong‐Parlung River from the Irrawaddy River and, subsequently, captured the Lohit River.