Geochronological and geochemical constraints on the subduction-modified lithospheric origin of the early Cretaceous volcanic rocks, in the western North Huaiyang Belt of Dabie Orogen, China

Abstract

Geochronological, elemental and Sr–Nd–Hf isotopic data for intermediate–acid volcanic sequences from the western North Huaiyang Belt of the Dabie Orogen, China, provide new constraints for the nature of the lithosphere and the potential involvement of subducted Yangtze crust. These rocks are calc-alkaline andesite, trachyandesite and dacite. They yield ages of 129–127 Ma and show a geochemical affinity to arc volcanic rocks. (87Sr/86Sr)i ratios and eNd(t) values range from 0.7065 to 0.7080 and −16.9 to −13.2, respectively. Zircon in situ eHf(t) values range from −29.4 to −20.2 and Hf model ages from 3.03 to 2.46 Ga. These volcanic rocks were likely derived from a hybridized source involving enriched lithosphere of the North China Craton (NCC) and deep-recycled continental crust of Yangtze Block. Our data, along with geological observations from early Cretaceous igneous rocks, suggest an east–west extensional magmatic pulse at 130–120 Ma along the entire North Huaiyang Belt. The extent of involvement of the Yangtze continental crust with the lithosphere of the NCC decreases from East to West. This reflects along strike changes in Triassic northward deep subduction and subsequent exhumation of the Yangtze crust. Further lithospheric extension in the early Cretaceous led to unrooting of the thickened lithosphere and generation of Cretaceous volcanic rocks along the North Huaiyang Belt. Supplementary material: Microprobe data for all samples are available at https://doi.org/10.6084/m9.figshare.c.4611911