Stepwise breakup of supercontinent Nuna: A synthesis with new ca. 1236 Ma paleomagnetic data from the North China craton

Abstract The timing and mechanisms by which the supercontinent Nuna broke up are still enigmatic, although the details have implications for global tectonic activity through Mesoproterozoic periods of alleged quiescence. The proposed breakup time of Nuna has ranged from ca. 1.6 to 1.2 Ga based on the episodic eruptions of large igneous provinces (LIPs) and associated large-scale continental rift systems. Paleomagnetic data from Proterozoic cratons can quantify their motions and directly test these competing inferences. In this study, new paleomagnetic results, which passed baked-contact tests and a reversal test, are reported from 32 dikes from the North China craton (NCC). An isotope dilution–thermal ionization mass spectrometry (ID-TIMS) baddeleyite date from one of these dikes constrains dike emplacement at 1235.6 ± 2.0 Ma, which provides a new, well-dated paleomagnetic pole (27.7°N, 168.5°E, A95 = 5.0°) for the NCC. Combined with the previously published 1.45–1.04 Ga paleomagnetic and geologic data from Laurentia, the NCC, Baltica, and Australia, the divergence of their apparent polar wander paths suggests that the core of Nuna (Laurentia, Baltica, and Siberia) broke up with East Nuna (Australia and the NCC) at ca. 1.38 Ga. Thereafter, the breakup of East Nuna, denoted by the separation of the NCC and Australia, occurred after ca. 1.32 Ga, and the breakup of the core of Nuna, denoted by the breakaway of Baltica from Laurentia and Siberia, occurred at ca. 1.26–1.22 Ga. The stepwise breakup process of Nuna was similar to that of Pangea, providing evidence for a robust tectonic regime in Earth’s middle age.