Nature and origin of the Wenquan granite: Implications for the provenance of Proterozoic A-type granites in the North China craton

Abstract

The Proterozoic Wenquan granite occurs at the northern margin of the North China craton. New U–Pb zircon ages reveal that the Wenquan granite was emplaced at 1697 ± 7 Ma, and is thus approximately coeval with the 1753 ± 23 Ma Changsaoying granite and the 1683 ± 4 Ma Shachang granite found in the area. The ubiquitous occurrence of titanite and magnetite demonstrates that the granites are oxidized. Geochemically, they show most of the characteristics of typical A-type granites, such as high contents of alkalis (i.e., high K 2O + Na 2O, with K 2O/Na 2O > 1), Rb, Y, Nb and rare earth elements (REE, except for Eu), high FeO t/MgO and Ga/Al ratios and low contents of CaO, Al 2O 3, and Sr. Their negative bulk rock initial Nd and zircon initial Hf isotopic ratios suggest that they were most likely derived from the late Archean lower crust. The three Proterozoic A-type granites are believed to be genetically related to the breakup of the Columbia supercontinent.