Revisiting early Neoproterozoic mafic sills in the North China Craton

• In situ U-Pb geochronology was conducted on the early Neoproterozoic mafic sills in the North China Craton. • Baddeleyite U-Pb age of 906.5 ± 1.1 Ma suggests a widespread ca. 907 Ma intrusive event. • Apatite U-Pb ages of 984 ± 64 Ma to 930 ± 57 Ma are consistent with zircon/baddeleyite ages. • New U-Pb ages constrained the depositional age of Huaihe Group at ca. 1121–907 Ma. Neoproterozoic Large Igneous Provinces (LIPs) continue to receive worldwide attention due to their genetic links with supercontinent dispersal and use in paleocontinental reconstructions, formation of ore deposits, climate shifts, and biological extinctions. However, their utility is hampered by a lack of high precision geochronology. Here we present a new U-Pb ID-TIMS baddeleyite age for a Neoproterozoic mafic sill intrusion in the North China Craton (NCC). A mafic intrusion within the Huaibei/Huaihe Group of Xuhuai Basin, previously dated between 915 Ma and 900 Ma (U-Pb zircon/baddeleyite LA-ICP-MS) gives a baddeleyite age of 906.5 ± 1.1 Ma. Given the wide occurrence of 915–900 Ma mafic intrusions dated previously, this new age potentially suggests a widespread ca. 907 Ma mafic intrusive event across NCC. Furthermore, this baddeleyite age constrained the Huaibei/Huaihe Group to have deposited in an age span of 1121–907 Ma. Apatite grains from the mafic sills have also been dated by U-Pb LA-ICP-MS, which produced dates that range from 984 ± 64 Ma to 930 ± 57 Ma, with errors similar to previous zircon/baddeleyite U-Pb LA-ICP-MS dates, indicating the feasibility of apatite U-Pb geochronology to constrain the timing of mafic intrusions. REE distribution patterns coupled with the Sr/Y-LREE discrimination plots demonstrate a primary origin for the dated apatite grains. Apatite crystallized from mafic magmas following earlier crystallization of feldspar that incorporated significant amounts of Eu. Recalculation of nearly 600 radio-isotopic data points on Neoproterozoic mafic intrusions in the NCC yield three age peaks at ca. 940 Ma, ca. 915 Ma and ca. 885 Ma, respectively. The major age peak at ca. 915 Ma is broadly consistent with our U-Pb ID-TIMS baddeleyite age that is suggestive of the main episode of mafic intrusion. Further high precision U-Pb ID-TIMS geochronology is necessary to precisely constrain the timing of the ca. 940 Ma and ca. 885 Ma mafic intrusions.