Timing and Petrogenesis of Early Devonian Intrusive Rocks in the Niukutoudong Area: New Constraints on Tectonic Evolution of the East Kunlun Orogen

The Niukutoudong deposit, in the Qimantage metallogenic belt, western East Kunlun Orogenic Belt, is a recently discovered cobalt-rich polymetallic deposit. This study integrates zircon U-Pb geochronology and whole-rock geochemistry of the ore-hosting intrusions to constrain their emplacement ages, petrogenesis, and tectonic setting, thereby constraining the Early Devonian tectonic evolution of the East Kunlun area. The geochronological results for four samples demonstrate that the granite porphyry, granite, granodiorite, and gabbroic diorite at Niukutoudong were emplaced in the Early Devonian (403.7–406.3 Ma). Geochemically, the granite, granodiorite, and gabbroic diorite are high-K calc-alkaline, metaluminous to weakly peraluminous I-type granitoids, characterized by consistent enrichment in LREEs, negative Eu anomalies, enrichment in LILEs, and depletion in HFSEs. The granite porphyry, by contrast, is a peraluminous A-type granite distinguished by elevated total REE contents, pronounced negative Eu anomalies, and high HFSE abundances. The regional source characteristics of coeval intrusions, integrated with key incompatible element ratios (e.g., Nb/Ta, Ba/Nb), imply that the Early Devonian Niukutoudong intrusions were probably generated through crust–mantle interaction. Integrated evidence indicates that the Niukutoudong intrusive rocks formed in a post-collisional extensional environment following the closure of the Proto-Tethys Ocean. The mixed crust–mantle signature common to both regional and local Early Devonian intrusive rocks indicates that the East Kunlun Orogenic Belt had already transitioned from syn-collisional crustal thickening into a post-collisional extensional stage by the Early Devonian, marked by lithospheric thinning, asthenospheric upwelling, and crust–mantle interaction. This magmatism records the tectonic regime shift and likely has a genetic link with the Niukutoudong Co-polymetallic mineralization, offering critical insights into the Qimantage metallogenic framework.