Late Paleozoic igneous rocks in the Xing’an Massif and its amalgamation with the Songnen Massif, NE China

Abstract

We present new zircon U–Pb–Hf isotopic and whole-rock geochemical data for late Paleozoic igneous rocks from the Xing’an Massif, Northeast China, to further our understanding of the amalgamation of the Xing’an and Songnen massifs. Zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb ages indicate that late Paleozoic magmatism occurred in the Xing’an Massif over three stages: during the early Carboniferous (359–352 Ma), early late Carboniferous (327–320 Ma), and late Carboniferous–early Permian (307–295 Ma). The early Carboniferous igneous rocks are mainly quartz diorite, granodiorite, monzogranite, syenogranite, and rhyolite, and formed in an active continental margin setting related to the westward subduction of the Heihe–Nenjiang oceanic plate. The early late Carboniferous monzogranites are medium-K calc-alkaline I-type granitoids, with zircon εHf(t) values of +5.6 to +13.0 and TDM2 ages of 973–502 Ma, suggesting that the primary magma was derived from the partial melting of newly-accreted crust. The early late Carboniferous igneous rocks formed in collisional setting, marking the amalgamation of the Xing’an and Songnen massifs. The late Carboniferous–early Permian intrusive rocks are dominated by diorite, monzogranite, syenogranite, alkali-feldspar granite, and granite porphyry. The large volume of alkali feldspar granites and A-type granites suggested that they formed in a post-collisional extensional environment.