Mesozoic exhumation and ca. 10 Ma reactivation of the southern Yin Shan, North China, revealed by low-temperature thermochronology

The thermochronological history of orogens along plate margins provides unique constraints on regional tectonic evolution. Given existing thermochronological data that identify late Mesozoic–Cenozoic multiphase cooling events, we perform new apatite fission-track and (U-Th)/He low-temperature thermochronology on Wula Shan and Dahong Shan rocks to reveal the first stages of cooling along the southern Yin Shan orogenic belt, northern margin of the North China Block (NCB). Our new thermal history modeling suggests that cooling of the southern Yin Shan began in the Late Triassic (ca. 230 Ma), with rapid cooling at ca. 210–178 Ma and ca. 10~ Ma in the Wula Shan and ca. 200–160 Ma in the southern Dahong Shan. Late Triassic-Early Jurassic cooling stages are related to uplift and exhumation of the northern NCB, which given the tectonic setting of the late Indosinian event, are mainly interpreted as signatures of Mongol–Okhotsk Ocean subduction. Subsequently, enhanced plate convergence of East Asia with closure of the Mongol–Okhotsk Ocean led to intense thrust-nappe and intracontinental orogeny during the early Yanshanian. Importantly, our new finding of ca. 10 Ma rapid cooling of the Wula Shan at a rate of ~3.5 °C/Ma corresponds to coeval uplift and synrift basin sedimentation in the Ordos Block periphery, western NCB, which could mark the response to craton-scale rotational deformation. The completion of this low-temperature thermochronological database allows us to reappraise the Mesozoic exhumation and ca.10 Ma reactivation history and its implications for the southern Yin Shan.