Continental collision and accretion recorded in the deep lithosphere of central China

Abstract Basaltic–andesitic volcaniclastic diatremes erupted in the Mesozoic (~ 160 Ma) in the Xinyang area, Henan Province of central China. The locality lies on the western margin of the Eastern Block of the North China Craton and the southern margin of this craton. The diatremes carry a suite of xenoliths including lower crustal mafic to felsic granulites, eclogites, meta-gabbros, pyroxenites and mantle peridotites. The petrological and geochemical data show that the crust in the area is temporally and compositionally zoned; exposed rocks up to ca 2.85 Ga old underlain by felsic granulites and rare pyroxenites with zircon ages of 3.6–3.4 Ga (to ca 30 km depth). Deeper (ca 30–45 km) parts of the lower crust consist of high-pressure mafic to felsic granulites and meta-gabbro, which give Paleoproterozoic (2.0–1.8 Ga) zircon ages. Our data show the significance of underplating/vertical crustal growth in the Paleoproterozoic, which was related to the amalgamation of the Eastern and Western Block of this craton and a global (Columbia) supercontinent assembly. Hf-isotope data indicate that both juvenile material and remelting of older (3.8–3.0 Ga) crustal rocks were involved in this important event. Paleozoic (440–260 Ma) and Early Mesozoic (228–219 Ma) zircons are also found in xenoliths from the deeper part of the lower crust and the uppermost mantle (i.e. eclogite and peridotite). They are interpreted as reflecting geodynamic processes related to the continental collision between this craton and the Yangtze Craton, respectively. The xenoliths from Xinyang diatremes thus record the growth and modification of the old (Paleo-Mesoarchean?) continental lithosphere by magma underplating during several tectonic events: assembly of the southern and northern parts of the Eastern Block in Neoarchean time, collision of the Western and Eastern Blocks along the Trans-China Orogen in the Paleoproterozoic, and subduction and collision of the Yangtze Craton with the North China Craton in early Paleozoic and Triassic times, respectively.