Petrogenesis of Triassic Granitoids in the Guide Area, Western Qinling: Implications for the Scissors-Like Subduction to Collision Orogenic Processes

Indosinian granitoids are widespread in the western Qinling Orogen, offering valuable insights into the geodynamic evolution of the Qinling Orogenic Belt and crust-mantle interactions. In this study, we present new zircon U–Pb dating, major and trace elemental analyzes, and Sr isotopic compositions of the Triassic granitoids from the Dangjiasi, Laxiwa, Guomaying, Guase, and Changmu intrusions in the Guide area, northwestern segment of the West Qinling. Geochemical and Sr isotopic compositions reveal that the granitoids in the Guide area of the Western Qinling were formed through the mixing of partial melting from ancient crustal rocks and mantle-derived melts. The rocks of the crustal source consist mainly of mafic meta-igneous rocks (particularly amphibolites) and some metasedimentary rocks. We also summarize previously published geochronological and geochemical data on the granitoid rocks in the West Qinling and adjacent areas. The granitoid magmatism was emplaced during two distinct magmatic pulses at ca. 265–230 Ma and 230–200 Ma. The early-phase magmatic rocks are linked to subduction settings, whereas the late-phase magmatic rocks are associated with syn-collisional to post-collisional environments. The age, geochemical, and isotopic variations from west to east across the Qinling Orogen suggest a scissor-like subduction-collision process, supporting the prevailing view that the orogeny resulted from the collision between the North China Craton and the South China Craton. This study advances our understanding of the crust-mantle interactions and tectonic evolution in the western Qinling Orogen.