The proposed Archean eclogite-facies metamorphism in the North China Craton has been used to argue for early modern-style plate tectonics, yet this interpretation is complicated by polymetamorphism and ambiguity in accessory-mineral geochronology. We integrate garnet Sm−Nd and Lu−Hf chronometry with zircon U−Pb dating, pseudosection modeling, and thermobarometry of these high-grade rocks. Our data do not support Neoarchean eclogite-facies metamorphism but reveal two distinct Paleoproterozoic metamorphic events. Lu−Hf dates identify a previously unrecognized ca. 2.1 Ga metamorphic episode associated with garnet growth, while Sm−Nd and zircon U−Pb dates (ca. 1.8 Ga) record cooling following craton amalgamation. Neoarchean zircon dates (2.47 Ga) represent inherited or reset domains. The 2.1 Ga event is interpreted as pluton-enhanced metamorphism during regional rifting, largely absent in the zircon record. These results show that polymetamorphic rocks may preserve key tectonothermal events that are undetected by zircon-only approaches, and highlight the necessity of integrated chronometry to resolve complex cratonic histories.
Yang et al. (Thu,) studied this question.