Exhumation history of the Shanxi Rift, Central Asia, derived from low-temperature thermochronology

The Shanxi Rift system in Central Asia is a prominent Cenozoic intraplate rift system within the North China craton that also preserves a record of Mesozoic contractional deformation. The overprinting phases of deformation complicate interpretations of its tectonic history. Here, we present new apatite fission-track (AFT) thermochronology data from the northern flank of the rift system and compile a large thermochronology dataset from around the Shanxi Rift. We also present a new seismic reflection profile for the central Datong Basin to investigate synkinematic basin sediments within the rift. Thermal inverse models of low-temperature thermochronology data reveal temporal and spatial variations in exhumation rates across the rift flanks. The northern rift started exhuming in the Late Jurassic- Early Cretaceous, whereas the central and southern flanks experienced mainly Cenozoic exhumation. Between 50 Ma and 30 Ma, exhumation rates diminished from south to north but markedly accelerated again after 20 Ma. These modeling results reveal that normal faulting along the rift flank was active between 40 Ma and 25 Ma coupled with basin subsidence. The main phase of rifting initiated in the Paleogene, with deformation propagating from southwest to northeast. Postulated Late Jurassic crustal shortening in the Shanxi Rift system followed by Early Cretaceous extension explain the ages in the north, and these dynamics were probably driven by west-dipping flat-slab subduction of the Izanagi (Paleo-Pacific) slab and subsequent slab rollback. Cenozoic rifting across the Shanxi Rift was caused by the combined impacts of Pacific slab dynamics and the growing margin of the Tibetan Plateau.