Inherited structure as a control on late Paleozoic and Mesozoic exhumation of the Tarbagatai Mountains, southeastern Kazakhstan

Abstract

Central Asia hosts the Tianshan, the largest intracontinental mountain belt in the world, which experienced major reactivation and uplift since the Oligocene in response to the collision of India with Asia. This reactivation was focused around pre-existing structures inherited from the Paleozoic tectonic history of the region. The significant Cenozoic tectonic reworking of Central Asia complicates efforts to understand earlier phases of intracontinental tectonics during the late Paleozoic and Mesozoic. The Tarbagatai Mountains of eastern Kazakhstan record a thermotectonic history that provides insight into the timing and distribution of intracontinental tectonic activity in Central Asia prior to the India-Eurasia collision. Apatite fission track and (U-Th-Sm)/He analysis of igneous samples from the Tarbagatai Mountains reveals two episodes of cooling as a result of exhumation following Paleozoic amalgamation. Initial intracontinental deformation during the Late Permian drove exhumation synchronous with activity along newly formed strike-slip faults spanning the Central Asian Orogenic Belt. The major Chingiz-Tarbagatai Fault was reactivated during the Early Cretaceous, driving localised exhumation along the fault. The relative lack of Cenozoic tectonic activity in the Tarbagatai Mountains means they provide unique insight into the broader thermotectonic evolution of Central Asia during the late Paleozoic and Mesozoic.