The Indosinian Granitoids of the Songpan–Garze–West Kunlun Orogenic Belt, China: Distribution, Petrochemistry, and Tectonic Insights

Abstract

During the Indosinian orogeny, the Songpan–Garze–West Kunlun orogenic belt experienced significant tectonic and magmatic activity, leading to the widespread emplacement of granitoid bodies. This study provides a detailed petrochemical and geochemical analysis of these granitoids, offering new insights into their tectonic settings and magmatic evolution. The granitoids of this belt are systematically categorized into arc calc-alkaline and arc tholeiitic granitoids (ACG and ATG), cordierite peraluminous and muscovite peraluminous granitoids (CPG and MPG), potassium calc-alkaline granitoids (KCG), and peralkaline granitoids (PAG) suites. ACG and ATG types dominate early magmatism (230–190 Ma), reflecting a convergent tectonic setting, while KCG and MPG types magmatism, respectively, emerged 10–20 Myr and 15–25 Myr later, during post-collisional extensional phases. Geochemical analyses show that ACG and ATG granitoids follow calcic and calc-alkalic trends, while KCG and MPG display alkalic characteristics. These findings align with the region’s tectonic transition from the closure of the Paleo–Tethys Ocean to Late Triassic transpressional deformation. This study enhances the understanding of granitoid petrogenesis and provides valuable implications for regional tectonic evolution and mineral exploration.