Devonian A-type granitic magmatism on the northern margin of the North China Craton: SHRIMP U–Pb zircon dating and Hf-isotopes of the Hongshan granite at Chifeng, Inner Mongolia, China

We report first data for the Devonian Hongshan A-type granite along the northern margin of the Precambrian North China Craton. The granite is rich in silica (SiO2 = 76.07–77.62 wt.%) and alkalis (Na2O + K2O = 8.45–8.78 wt.%), but poor in calcium (CaO = 0.28–0.70 wt.%) and magnesium (MgO = 0.08–0.20 wt.%). Chondrite-normalized REE patterns for the samples from the Hongshan granite show significant negative Eu anomalies (Eu/Eu* = 0.13–0.19). They contain high Rb, Ga, Y, Nb, and Zn, but low Ba and Sr contents, and in the multi-element spider diagrams normalized to primitive mantle, they show a similar pattern to that of A-type granites, such as negative Ba, Nb, Ta, Sr, P and Ti anomalies. Geochemical plots also show an affinity with A-type granites and suggest a post-orogenic setting (A2 type granite). SHRIMP U–Pb zircon dating yielded a concordant weighted mean 206Pb/238U age of 387 ± 4 Ma, which defines a Devonian magmatic event. The zircons have negative εHf(t) of − 8.4 to − 11.5 and give old Hf model ages of TDM2 = 2548–2820 Ma (mean 2667 Ma). Most 176Hf/177Hf and εHf values display Hf-isotope evolutional line of the lower continental crust. These results suggest that the Hongshan granite originated from melting of Archaean lower crust beneath the North China Craton in a post-orogenic extensional setting during the Devonian.