Heterogenous zircons from Mesozoic igneous rocks in the North China Craton and their tectonic implications
MIAO Laicheng1, FAN Weiming1, ZHANG Fuqin1 and LIU Dunyi2 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2. Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
Based on a synthesis of zircon inheritance from Mesozoic igneous rocks in the eastern portion of the North China Craton (NCC), it is proposed that inherited zircons with Neoproterozoic ages identified from these rocks are of a heterogenous derivation from the Yangtze/South China block, rather than from the NCC itself. The mechanism that introduces these zircons incorporated into the NCC is likely by tectonic underplating during the Triassic continental subduction of the Yangtze block beneath the NCC. Tectonic addition of abundant crustal materials represented by the heterogenous zircons into the NCC, probably along Moho or weak interfaces within the NCC’s crust, led to the crustal thickening in the NCC. These heterogenous materials, either as (partial) source rocks or as contaminants of the magmas generated during an extension environment following the crustal thickening, were reworked and therefore have significant contribution to petrogenesis of the Mesozoic igneous rocks. The crustal thickening resulted from the tectonic underplating, as indicated by the distribution extent of the heterogenous zircons, is spatially similar to that of the lithospheric thinning, with both mainly occurring in the eastern segment of the NCC. This is probably suggestive of an intrinsic relation between the thickening and thinning events during the Mesozoic evolution of the NCC.