Abstract
Andesitic arc magmas play a fundamental role in constructing continental crust, yet the long-term operation of crystal mush systems often homogenizes their isotopic signatures, obscuring the discrete contributions of mantle- and crust-derived end-members. To overcome this limitation, this study integrates whole-rock geochemistry, zircon U-Pb-Hf isotopes, and in situ apatite trace-element and SrNd isotopic analyses to unravel the magmatic evolution of the Nanshankou intrusive complex in the East Kunlun orogen, Northern Tibet Plateau. The complex comprises coeval (ca. 245 Ma) mafic to felsic intrusions, including amphibole gabbro, gabbroic diorite, quartz diorite, mafic microgranular enclaves, granodiorite, and monzogranite. Mafic units record derivation from a depleted mantle wedge metasomatized by sediment-derived melts during Paleo-Tethyan subduction. In contrast, the intermediate to felsic rocks display broad compositional and isotopic ranges in zircon εHf(t), apatite εNd(t), and REE contents, reflecting progressive crust-mantle hybridization, repeated mafic recharge, internal self-mixing, and late fractional crystallization within a long-lived crystal mush. The results show that mixing between juvenile mafic magmas and ancient lower crust produced isotopically less evolved felsic intrusions, illustrating how subduction-driven magma addition rejuvenates continental crust in arc settings. This study demonstrates the exceptional sensitivity of apatite for tracking magma mixing and provides new constraints on the mechanisms governing compositional diversity in arc magmatic systems.
• Apatite records mafic recharge and crust-mantle hybridization that collectively govern arc magma diversity.
• Crystal mush systems reveal unique pathways of magma hybridization.
• Mantle-derived magmas shift felsic melts toward juvenile isotopic signatures, promoting crustal rejuvenation.