Meso-Cenozoic Exhumation of the Altai-Sayan Region: Constrained by Available Low-Temperature Thermochronology

Based on a compilation of AFT, AHe ages and apatite MTLs from previous studies, the following conclusions can be made regarding the spatial and temporal distribution of exhumation in Altai-Sayan region. The oldest AFT ages, found in the Gobi Altai, suggest that this region has been tectonically stable since the Late Jurassic. Early Cretaceous rapid cooling is focused in northern Chinese Altai and western Gorny Altai, associated with the Mongol-Okhotsk orogeny. Late Cretaceous rapid cooling identified in most other areas of Altai-Saya region is best explained as being associated with fault reactivation due to the subsequent collapse of the Mongol-Okhotsk Orogen. Cenozoic reactivation is difficult to be record with low-temperature systems due to very limited exhumation over this time frame. As a result, the timing and mechanism of any Cenozoic reactivation in the Altai-Saya region remains unclear. At the orogenic scale, the AFT ages in the northern part of the Altai-Saya region are younger than those in the southern part, indicating that the basement of northern part, weakened by its earlier extensional tectonism, was more easily reactivated.