Petrogenesis of Late Neoarchean Sanukitoids in the Western Shandong Province, North China Craton: Implications for Crust–Mantle Interactions

The late Neoarchean marks a major transition from juvenile crust production to the compositional and structural maturation of continental crust, but the respective roles of subduction-related crustal recycling and intracrustal reworking in this transition remain poorly constrained. Sanukitoids record complex Archean crust–mantle interactions and provide insights into continental crustal evolution. Here, we present new petrological, whole-rock geochemical, and zircon U–Pb isotopic data for late Neoarchean sanukitoid-affinity quartz monzodiorites from Western Shandong Province. Zircon U–Pb dating yields crystallization ages of 2542 ± 15 Ma (LX2423) and 2485 ± 20 Ma (LX2426-1). The quartz monzodiorites have low SiO2 (57.00–59.52 wt.%), high MgO (4.58–6.73 wt.%), high Mg# (60.8–65.9), variable K2O/Na2O ratios (0.31–0.63; mostly 0.58–0.63), strongly fractionated REE patterns ((La/Yb)N = 12.28–39.92), and pronounced negative Nb–Ta–Ti anomalies, consistent with Archean sanukitoids. Petrogenetic modeling suggests low-degree (<10%) partial melting of a mantle source modified by slab-derived melts and fluids, documenting subduction-related recycling of slab-derived components into the mantle source. We therefore interpret the quartz monzodiorites as evidence for crust–mantle material recycling and mantle-derived magmatic addition, rather than as direct products of crustal reworking. In combination with coeval high-K granites that reflect melting of pre-existing crust, our results support a model in which slab rollback may have coupled crustal recycling and mantle-derived addition with intracrustal reworking, thereby promoting compositional diversification during the late Neoarchean maturation of continental crust.