Mantle Sources and Petrogenesis of Cenozoic Basalts in Minqing Area of Fujian Province, SE China

ABSTRACT

Cenozoic intraplate basalts in SE China provide a crucial window into deep mantle recycling and Palaeo‐Pacific plate subduction dynamics. However, the petrogenesis of the transitional ‘central belt’ remains poorly constrained compared to its coastal and inland counterparts, hindering a comprehensive understanding of the lithospheric mantle beneath South China. This study presents new high‐precision ⁴⁰ Ar‒ ³⁹ Ar geochronological, geochemical and Sr‒Nd‒Pb isotopic data for alkaline basalts from Minqing, Fujian. Dating yields a plateau age of 13.15 ± 0.92 Ma, establishing a distinct coastal‐to‐inland younging trend driven by slab rollback. Geochemically, these basalts exhibit ocean island basalt (OIB)‐like trace element patterns with pronounced negative Ti and K anomalies, alongside high Zr/Hf ratios. These geochemical fingerprints strongly indicate the involvement of recycled sedimentary carbonate components in the mantle source. Sr‒Nd‒Pb isotopic compositions reveal mixing between depleted mantle (DM) and enriched mantle II (EM2) end‐members. Quantitative trace element modelling demonstrates that these basalts originated from a hybrid source dominated by carbonated garnet pyroxenite with minor garnet peridotite. We propose that this mantle source was metasomatised by carbonate‐rich melts derived from the subducted Palaeo‐Pacific slab within the Big Mantle Wedge (BMW). This mechanism highlights the crucial role of deep carbon recycling in generating subcontinental mantle chemical heterogeneity.