Zircon U–Pb constraints on the origin of UHP meta-supracrustal rocks in the Southern Sulu orogen, eastern China

Abstract

Most zircons in marble and quartzite, typical meta-sedimentary rock from southern Sulu orogenic belt, have a core-rim structure, including an inherited detrital core and a metamorphic overgrowth rim. A few zircons are completely metamorphic. Most detrital cores have relatively high REE contents and Th/U ratios and yield highly variable 206Pb/ 238U ages ranging from 2828 to 211 Ma, with major age populations at ∼1800 Ma and ∼800 Ma for quartzites and ∼1300 Ma for marbles. In contrast, the metamorphic zircon rims have relatively low REE contents and low Th/U ratios, and yield consistent Triassic metamorphic ages with a weighted mean age of 231 Ma. These results indicate that the marble and quartzite, together with eclogite and orthogneiss from the southern Sulu orogenic belt, have been subjected to a coeval Triassic UHP metamorphism. The protoliths of the quartzites may have been formed in the Neoproterozoic, whereas the protoliths of the marble are probably in the Mesoproterozoic. The source regions of the UHP supracrustal rocks underwent Neoproterozoic to Paloproterozoic tectonic–thermal events, indicating that the protoliths of the Sulu UHP rocks were derived from the Yangtze craton, instead of the North China craton.