Tracing Continental Basalt Sources and Mantle Processes Using Fe Stable Isotopes

Abstract Iron (Fe) isotopes have emerged as powerful tracers of mantle source heterogeneity and melting processes, yet the mechanisms producing heavy Fe isotope signatures (high δ 57 Fe values) in intraplate basalts remain debated. Competing interpretations include partial melting of recycled pyroxenite domains versus carbonate‐induced oxidation of a mantle source. Here we present new high precision Fe isotope data together with whole rock elemental and Sr‐Nd‐Pb‐Hf isotopic compositions of Cenozoic Chifeng basalts from eastern China to test the above hypotheses. Fractionation corrected bulk‐rock δ 57 Fe values of Chifeng basalts vary from +0.08‰ to +0.30‰, which cannot be readily explained by either magmatic processes or mantle oxidation. Systematic covariations of δ 57 Fe with SiO 2 , trace element ratios (Nb/Zr, Ce/Pb, and Gd/Yb), and radiogenic isotopes ( 143 Nd/ 144 Nd and 206 Pb/ 204 Pb) demonstrate that Fe isotope variations are closely linked to source heterogeneities. Quantitative modeling reveals a positive correlation between pyroxenite‐melt fraction and δ 57 Fe value, indicating that variations in pyroxenitic input likely control the Fe isotopic compositions of Chifeng basalts. In fact, the Indian‐type Pb isotope signatures together with the heavy δ 57 Fe values of Chifeng basalts are best accounted for by recycled Pacific oceanic crust that was hybridized with subducted sediments and subsequently incorporated into the asthenosphere beneath eastern China. The integrated Fe–Nd–Pb isotope data further support melt–melt mixing between pyroxenite‐derived and peridotite‐derived melts within the lithospheric mantle. Therefore, the Fe isotope signatures of Chifeng basalts record source lithological heterogeneity linked to recycled pyroxenites and demonstrate the utility of Fe isotopes in resolving mantle processes.