LAUSR

Abstract Central Inner Mongolia is located in the southeastern segment of the Central Asian Orogenic Belt (CAOB), and controversy has long surrounded its late Paleozoic tectonic evolution. Here, we present an integrated study of zircon U-Pb ages, whole rock major and trace elements, and zircon Hf isotopes for five less studied alkali feldspar granitic plutons in the Dongwuqi area to the north of the Erenhot-Hegenshan-Heihe suture zone. Zircon U–Pb dating by laser ablation-inductively coupled plasma–mass spectrometry (LA–ICP–MS) indicates that these granitic plutons were emplaced in the Late Carboniferous (315–300 Ma). The Late Carboniferous alkali feldspar granites belong to high-K calc-alkaline series and are evolved I-type granites. They are high in SiO2 (73.22–77.36%), and low in MgO (0.07–0.49%) with enrichments in light rare earth elements (LREEs), Zr, Hf, Rb, Th, and U, and depletions in Ba, Nb, Ta, Sr, and Eu. The Dongwuqi granitic rocks are characterized by high positive zircon eHf(t) values (+7.6 to +15.1), and relatively young two-stage Hf model (TDM2) ages (364–835 Ma). These geochemical data, together the common miarolitic texture, indicate that they were derived from partial melting of juvenile arc-related mafic to intermediate rocks in the lower crust, and eventually emplaced in low-pressure conditions or at shallow crustal levels, with involvement of extensive fractional crystallization during magma evolution. Our new results, along with the published regional data, delineate a NE-trending Carboniferous continental arc belt (more than 1700 km) in the northern accretionary zone of the Erenhot-Hegenshan-Heihe suture. Accordingly, we invoke that the Dongwuqi Late Carboniferous high-K granites were emplaced in an active continental margin setting, which was probably related to the northwestward subduction of the Hegenshan oceanic plate beneath the Xing'an-Uliastai-Nuhetdavaa block.