Petrogenesis of typical Mesozoic and Cenozoic volcanic rocks from the North China Craton: new evidence from Hf isotopic studies

High precision Hf isotopic data are firstly reported for the typical Mesozoic and Cenozoic volcanic rocks (alkaline basalts, tholeiites. and high-Mg andesites) from the North China Craton in this paper. The results show that these Mesozoic and Cenozoic volcanic rocks have completely different Hf isotopic compositions with a large range in epsilon(Hf) (t) values (-18.4 similar to 9. 6) with an excellently positive correlation between Hf and Nd isotopes. Among them, the Cenozoic Changle-Linqu and Late Cretaceous Jianguo (similar to 105 Ma) alkaline basalts possess very high Hf and Nd isotopic compositions (epsilon(Hf) (t) = 6.8 similar to 9.6; epsilon(Nd) (t) = 0.4 similar to 4. 9), indicating their derivation from the undifferentiated asthenospheric source. Early Cretaceous Fangcheng (125Ma) alkaline basalts and tholeiites have extremely low Hf and Nd isotopic ratios (epsilon(Hf)(t) = -15.6 similar to -18.4; epsilon(Nd) (t) = -12.8 similar to -14.4), representing their origination from an enriched sub-continental lithospheric mantle. Wulahada (142Ma) high-Mg andesites show relatively lower Hf and Nd isotopic ratios (epsilon(Hf)(t) = -2.1 similar to -2.6), implying a derivation from old refractory lithospheric mantle contaminated with melt fulid released from subducted crustal materials. Relatively larger variations in Hf isotopic compositions of basalts (epsilon(Hf) (t)/epsilon(Nd) (t) > 1 demonstrate that the Hf isotopes could be better tracer of mantle sources than the Nd isotopes.