Large-scale Early Cretaceous volcanic events in the northern Great Xingʹan Range, Northeastern China

The Great Xingʹan Range in northeastern China is characterized by large-scale Mesozoic magmatism, and forms a key part of the NE-trending Mesozoic magmatic belt in East China. However, only limited precise age data for the volcanic rocks in this belt were previously available, which significantly hampers understanding of the petrogenesis and geodynamic setting of these rocks. Systematic dating of volcanic rocks in the Great Xingʹan Range was undertaken in order to rectify this situation. The Mesozoic volcanic rocks in the area have been sub-divided into the Tamulangou, Shangkuli and Yilieke formations. The Tamulangou and Yiliekede formations are composed of basalt and basaltic andesite, whereas the Shangkuli Formation consists of rhyolite and dacite. Zircon U–Pb and whole rock 40Ar/39Ar dating, combined with published data, indicate that the Tamulangou Formation was formed over a large time interval from the Early Jurassic to Early Cretaceous; it should therefore not be regarded as a single stratigraphic unit. In contrast, volcanic rocks of the Shangkuli and Yiliekede formations were erupted in the Early Cretaceous, between 125–115 Ma. Overall, most Mesozoic volcanic rocks in the Great Xingʹan Range were erupted during the Early Cretaceous with an age peak at ∼ 125 Ma, coeval with the time of lithospheric thinning in the eastern part of the North China Craton. Therefore, the Great Xingʹan Range constitutes an important area that records a significant Early Cretaceous giant igneous event in eastern China. It is possible that this activity was related to subduction of the Pacific plate during the Late Mesozoic, as has been suggested to explain crustal thinning of the North China Craton.