Geochemistry of cenozoic basaltic rocks from Anhui province, China: implications for their petrogenesis and mantle processes

Abstract

Continental intraplate basalts exhibit diverse geochemical characteristics that reflect complex mantle processes beneath East Asia. In eastern China, the tectonic evolution of the North China Craton has been linked to lithospheric thinning, asthenospheric upwelling, and metasomatic modification associated with Pacific slab subduction. However, the petrogenetic mechanisms and mantle source characteristics of the Cenozoic basalts in Anhui Province remain inadequately constrained. Here we show that the geochemical and isotopic compositions of basalts from Anhui Province indicate a heterogeneous mantle source modified by carbonatitic metasomatism. Major and trace element analyses, REE patterns, and Sr-Nd isotopic data reveal three primary magma types—alkali basalts, tholeiitic basalts, and Nushan alkali basalts—formed through varying degrees of partial melting (1–5 vol%, 15 vol%, and 1–10 vol%, respectively) followed by fractional crystallization. Trace element ratios (e.g., Zr/Sm–Hf/Sm, La/Nb–⁸⁷Sr/⁸⁶Sr) suggest that the mantle beneath Anhui underwent enrichment by carbonated eclogite-derived melts related to subducted Pacific slab materials. The isotopic compositions indicate a mixing of depleted MORB mantle (DMM) and enriched mantle type-1 (EM-1) sources, with younger basalts showing more depleted signatures. These findings provide new insights into the long-term geochemical evolution of the subcontinental lithospheric mantle beneath eastern China and highlight the importance of multi-stage metasomatism and subduction-derived enrichment in shaping the region’s intraplate magmatism.