Detrital zircon U–Pb dating and whole-rock geochemistry from the clastic rocks in the northern marginal basin of the North China Craton: Constraints on depositional age and provenance of the Bayan Obo Group

Abstract

Located in the northern margin of the North China Craton (NCC), the Bayan Obo Group is composed of low-grade metamorphic clastic rocks and carbonates unconformably overlying the Archean–Paleoproterozoic basement and is famous for its hosting of the world's largest REE ore deposit. It has long been debated whether the Bayan Obo Group was correlated with the Proterozoic sedimentary records of the Xiong’er and Yanliao rifts or whether it was an analog of the Paleozoic Sailinhudong Group. In this study, we present new U–Pb data from detrital zircons which constrain the maximum depositional ages of the Dulahala and Halahuogete formations of the Bayan Obo Group as 1822±9Ma and 1710±29Ma, respectively. Our geochronological and geochemical data suggest that the major provenance of the Dulahala and Jianshan formations was the Paleoproterozoic khondalites which were deposited during 2.0–1.95Ga and metamorphosed during 1.95–1.82Ga, whereas the sediments of the Halahuogete and Bilute formations were derived from various sources in the NCC. Combining our data with the pioneer's researches, it appears that the northern marginal rift system of the NCC resulted from two discrete rifting events, which were probably related to the initial intra-continental extension and the final breakup of the Columbia Supercontinent.