Post-Orogenic Tectonic Evolution of the Jiangnan-Xuefeng Orogenic Belt:Insights from Multiple Geochronometric Dating of the Mufushan Massif,South China

The Mufushan massif, as continental intra-plate magmatites located in the Jiangnan-Xuefeng orogenic belt of the South China. The Mufushan massif constitutes the largest Mesozoic intrusive complex, intruded the Mesoproterozoic Lengjiaxi Formation. Multiple geochronometric dating was used to reconstruct their evolution from emplacement to exhumation. The Mufushan granitoids were emplaced at ～150 Ma（U-Pb zircon） as post-orogenic magmatites contributing to Triassic crustal thickening. Onset of regional extension at ～128 Ma(40Ar/39Ar white mica and biotite) manifests a tectonic regime switch. Intense exhumation prior to ～55 Ma was followed by slow denudation and peneplanation for the next 37 Ma（～55–18 Ma）. Accelerated cooling since ～18 Ma may have been caused by a far-field effect of the collision between IndiaAsia Plate or the Pacific-Plate subduction. Through a multi-geochronometric approach, this study provides a new comprehensive model for the cause of the intra-plate magmatism formation in the South China, and also established a reliable geochronological framework of the post-orogenic tectonic evolutions of the Jiangnan-Xuefeng orogenic belt.