Zircon U-Pb age and Hf isotopic characterization of the Niutishan dolerite sills in the Northern Jiangsu Region and their geological implication

The northern Jiangsu region is located in the southeast margin of the North China Craton, and the Neoproterozoic sedimentary rocks in this region are widely distributed with dolerite sill swarms. The chronology of these dolerite is still in the preliminary stage, and the existing diagenetic ages are inconsistent with the Sinian strata. Zircon U-Pb dating and in situ Hf isotope characterization were studied on the dolerite from the Niutishan region, which intrude into the Niyuan Formation in midsill-shaped. Zircon LA-ICP-MS U-Pb dating results indicate that the formation age of these dolerite is 962.3±8.5 Ma, suggesting the existence of Neoproterozoic magmatic activity in this area. The εHf(t) values of these zircons range from 8.48 to 11.92, showing consistent positive values. The first-stage Hf model age (tDM1) and the second-stage Hf model age (tDM2) were 1220~1063 Ma and 1301~1095 Ma, respectively. Together, these data indicate that the primordial magma may have risen directly from the lithospheric mantle to the surface and may have originated from a Mesoproterozoic transitional mantle. Based on the chronology of Niutishan dolerite and Hf isotopic characteristics of zircon, combined with the research progress of the Rodinia supercontinent, it can be inferred that magmatic processes related to the breakup of the Rodinia supercontinent may have occurred in the southeast margin of the North China Craton in the early Neoproterozoic.