Tectono-thermal evolution of the Kanggur-Huangshan shear zone, Chinese Tianshan: Insights from integrated geochronology and thermochronology

Abstract

Integrated geo-thermochronometry with structural analysis provide insights into the deformation and exhumation processes within the Kanggur-Huangshan shear zone (KHSZ), a significant transcurrent strike-slip fault and metallogenic belt in the Eastern Tianshan orogenic belt (Central Asia). Previous studies have primarily focused on structural, geochronological and geochemical aspects, often overlooking the exhumation dynamics. This study employs zircon U-Pb, (U-Th)/He (ZHe), apatite fission track (AFT) and (U-Th)/He (AHe) dating alongside field observations and microstructural analysis to elucidate the unroofing processes in the western KHSZ. New zircon U-Pb ages ranging from 280 to 260 Ma and U-Th/He age between 215 and 180 Ma for synkinematic rock, combined with published Ar/Ar data, indicate rapid post-magmatic cooling and shearing in an extensional setting. Subsequently, the region underwent tectonic inversion to transpression and exhumation, with blocks inside the shear zone experiencing more exhumation and forming the positive-flower structures until ca. 200 Ma. Late Jurassic to earliest Cretaceous AFT ages (165–145 Ma) and overlapping AHe ages (155–145 Ma) suggest rapid cooling after differential Jurassic burial, followed by a gradual exhumation of the samples to near-surface levels. A synthesis of existing data indicates that moderate Mesozoic cooling, coupled with Jurassic reburial and Cretaceous-Cenozoic tectonic quiescence, is characteristic of the western KHSZ. This geological history is crucial for understanding the preservation of porphyry Cu deposits as well as epithermal gold and Fe-Cu deposits in the region.