Reworking of Yangtze crust into the mantle lithosphere of the North China Craton along the Dabie–East Qinling Orogen: Evidence from the Early Cretaceous volcanic rocks

Abstract

Abstract Mineral chemistry, zircon U-Pb geochronology, and elemental and Sr-Nd-Pb-Hf-O isotopic data for the Early Cretaceous volcanic rocks from the Dabie and East Qinling orogens of China constrain the reworking history of the Yangtze crustal materials in the North China lithosphere. These data provide new insights into the recycling of the deepsubducted crustal materials into the mantle and the transformation process from continental subduction to collision. Our data show that the Early Cretaceous volcanic rocks are characterized by shoshonitic and high-K calc-alkaline basaltic trachyandesite, trachyandesite, and trachyte. They synchronously erupted at ca. 135–120 Ma, and have zircon in situ εHf(t) values ranging from −29.0 to −17.2, and δ18O values from 4.89‰ to 6.84‰. These samples share similar “crust-like” geochemical signatures, whole-rock enrichment in the large-ion lithophile elements, depletion in high field strength elements (Nb/La = 0.12–0.38), highly enriched Sr-Nd isotopic compositions, as well as (206Pb/204Pb)i = 15.97–17.59, (207Pb/204Pb)i = 15.33–15.54, and (208Pb/204Pb)i = 36.87–38.59. The εNd(t) values range from −24.4 to −15.6, −21.8 to −13.1, and −16.8 to −10.9 for the eastern and western North Huaiyang belts of the Dabie Orogen and the East Qinling Orogen, respectively. Such geochemical similarities suggest that the northward deep-subduction of Yangtze crustal materials have been reworked into the North China Craton enriched lithospheric mantle. The spatial pattern of the Early Cretaceous volcanic rocks suggests that the Yangtze subduction extended northward beyond the southern margin of the North China Craton and ran into its interior. The surface and deep lithospheric boundaries are decoupled between the Yangtze Block and North China Craton. The Early Cretaceous igneous rocks in the Dabie–East Qinling Orogen were induced in response to the post-collisional unrooting of the Triassic over-thickened lithosphere coupling.