Geochronology, geochemistry and geological sig-nificance of the Early Cretaceous alkali feldspar granites in the Yilehuli Mountain, Da Hinggan, Mountain

Petrographic and geochemical data and LA-ICP-MS zircon U-Pb ages were obtained for Early Cretaceous alkali feldspar granites of the Yilehuli Mountain. The major elements of Yilehuli alkali feldspar granites are high in Si, ALK, and low in Mg, Ca. Trace elements are enriched in incompatible elements such as K, Rb and Th, and depleted in Sr, P, Eu and Ti. Geochemical features indicate that alkali feldspar granites are aluminum A-type granites (A/CNK=0.88~1.21, A/NK=0.94~1.49). LA-ICP-MS zircon U-Pb age data of coarse-medium alkali feldspar granites and fine-medium alkali feldspar granites are 140.3 ±1.0Ma and 137.9 ±0.8Ma, respectively, indicating that intrusive rocks were formed in Early Cretaceous. Combined with regional geological investiga-tion, the authors hold that the formation of Yilehuli plutons was closely related to lithospheric extension caused by closure of the Mongol-Okhotsk Ocean, and that the primary magma was derived from partial melting of crustal materials.