Mid-Mesoproterozoic diabase dyke swarms from the northern North China Craton: implications for breakup of the Columbia supercontinent

Diabase dyke (or sill) swarms are widespread within the Mesoproterozoic marine clastic and carbonate platformal sedimentary rocks in the northern North China Craton (NCC). Our new LA-ICP-MS zircon and baddeleyite dating on a diabase dyke sample emplaced into the Mesoproterozoic Wumishan Formation near Chaoyang in western Liaoning Province yielded weighed mean 207Pb/206Pb ages of 1345+/-12 Ma (95% confidence, MSWD=1.8, N=18) and 1353+/-14 Ma (95% confidence, MSWD=0.67, N=15), respectively, indicating emplacement of the dyke swarms at the Mid-Mesoproterozoic (Ectasian) instead of the Late Paleozoic or Mesozoic as previously regarded. Existence of the large volume of the Mid-Mesoproterozoic diabase dyke swarms in the northern NCC indicates that the northern NCC underwent strong extension and mafic magmatism during the Mid-Mesoproterozoic (Ectasian), probably related to breakup of the Columbia (Nuna) supercontinent. Compared with the 1.4-1.3 Ga mafic dyke swarms in other cratons, we suggested that the NCC is a member of Nena including the Laurentia (North America and Greenland), Siberia and Baltica cratons in the supercontinent. The NCC is likely connected to the Siberia and North America (Laurentia) cratons during the late Paleoproterozoic to Mid-Mesoproterozoic, and breaking of the NCC away from the Columbia supercontinent occurred from 1.35 Ga, which are consistent with the paleomagnetic results. The new zircon and baddeleyite geochronological results on the diabase dyke swarms provide not only magmatic evidence for Precambrian supercontinent reconstruction but also important constraint on ages of the Meso-Neoproterozoic strata in the NCC.