Cenozoic unroofing history of the Ladakh Batholith, western Himalaya, constrained by thermochronology and numerical modelling

International audienceThe Ladakh Batholith is part of the Transhimalayan Plutonic Belt, which crops out north of the Indus Suture Zone. We propose that the exhumation history of the Ladakh Batholith is linked to the tectonic, magmatic and erosion history of the Karakoram terrane and SW Tibet. We present new multiple low-temperature thermochronometry data (zircon (U–Th)/He, apatite fission-track and apatite (U–Th)/He) to gain insight into the cooling history of the Ladakh Batholith and recognize key periods in the evolution of the region. From the Indus Valley northwards the ages decrease across the batholith for all three thermochronometers applied. A model is proposed in which magmatism in the Ladakh Batholith ceased in the Late Eocene and initial denudation was driven by topographic uplift caused by collision. Southward tilting of the batholith occurred in the Late Palaeogene. This tilting resulted in an asymmetric topography with increasing elevation to the north. Strong erosion occurred in this northern region whereas the southern margin was affected by northwards thrusting of the Indus Molasse. For the first time, clear temporal and spatial variations in exhumation rate are identified in this region, highlighting why sampling strategy is critical in documenting exhumation changes in active tectonic settings