Late Mesozoic exhumation of metamorphic core complexes from the Xiaoqinling to Dabie orogen, central China: a record of Paleo-Pacific slab rollback

A series of metamorphic core complexes, including the Xiaoqinling, Xiong’ershan, and Dabie Mountains, span from west to east within the Qinling-Dabie Orogen of Central China. Despite their similar formation timelines and tectonic trends, they exhibit distinct geochemical signatures and exhumation processes. In the Xiaoqinling region, magmatic source temperatures initially increase with depth from approximately 606°C, reaching a peak around 847°C, and then decrease to approximately 660°C at greater depths, whereas in the Xiong’ershan area, they consistently decrease (811→609°C). The Dabie Mountains show consistent source temperatures (~800°C) across depths, suggesting their location above the ‘kink’ of Late Mesozoic Pacific subduction mantle wedge. Multi-method thermochronological analysis indicates that from 139 Ma to 85 Ma, the Xiaoqinling region cooled at 15.1°C/Ma initially, followed by deceleration to 2.7°C/Ma. Similarly, the Xiong’ershan and Dabie Mountains experienced two-stage exhumation processes, with cooling rates of 10.2°C/Ma, 3.7°C/Ma, and 20.3°C/Ma, 3.2°C/Ma, respectively. High-angle subduction and rollback of the ancient Pacific Plate during the Jurassic–Cretaceous transition facilitated the formation and rapid exposure of these metamorphic core complexes. Subsequent Pacific subduction reorientation during the Late Cretaceous reduced regional extension and thereby decreased the uplift and exhumation rates of these complexes.