Early Cretaceous Exhumation of the Southern Great Xing’an Range, Northeastern China: Evidence from (U-Th)/He and Fission-Track Thermochronology

The southern Great Xing’an Range in southeastern Inner Mongolia, north of the North China Craton, is a region influenced by different tectonic regimes. The Mesozoic–Cenozoic geological and topographic evolution remains controversial. In this study, we decipher the thermal evolution of the southern Great Xing’an Range by applying zircon and apatite (U-Th)/He and apatite fission-track thermochronology to granitoids to constrain the history of exhumation induced by the superposition of different tectonic activities and the history of geomorphological evolution. Zircon (U-Th)/He dating yields Early Cretaceous ages (109.1–134.9 Ma) and one early Permian age (292.0 Ma). Apatite (U-Th)/He dating and fission-track dating yield Early Cretaceous to early Late Cretaceous ages of 89.8–117.6 and 97.8–99.9 Ma, respectively. Combining these ages with previously published zircon U-Pb data and thermal history modeling, we suggest that the southern Great Xing’an Range experienced rapid cooling and exhumation during the Early Cretaceous. This cooling stage coincided with widespread extensional tectonics in northeastern China, which are thought to have been induced by the postorogenic collapse of thickened crust associated with the Mongol-Okhotsk Ocean and backarc extension associated with subduction of the Paleo-Pacific plate. This study implies that the southern Great Xing’an Range does not record significant exhumation during the Cenozoic.