The 1.35 Ga diabase sills from the northern North China Craton: Implications for breakup of the Columbia (Nuna) supercontinent

Diabase sills 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 sill sample emplaced into the Mesoproterozoic Wumishan Formation yielded weighed mean Pb-207/Pb-206 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 sills at the Mid-Mesoproterozoic (Ectasian) instead of the Late Paleozoic or Mesozoic as previously regarded. Existence of large volumes of 1.35 Ga diabase sills in the northern NCC indicates that the northern NCC underwent strong extension and mafic magmatism during Mid-Mesoproterozoic (Ectasian) time, probably related to the breakup of the Columbia (Nuna) supercontinent. Compared with the 1.4-1.3 Ga mafic dyke swarms (sills) in other cratons, we suggested that the NCC was a member of Nena including the Laurentia (North America and Greenland), Siberia and Baltica cratons in the supercontinent. The NCC was likely connected to the Siberia and North America (Laurentia) cratons during late Paleoproterozoic to Mid-Mesoproterozoic times, and breakup of the NCC away from the Columbia supercontinent occurred at around 1.35 Ga, which are consistent with the paleomagnetic results. The new zircon and baddeleyite geochronological results on the diabase sills provide not only magmatic evidence for Precambrian supercontinent reconstruction but also important constraint on ages of the Meso-Neoproterozoic strata in the NCC. (C) 2009 Elsevier B.V. All rights reserved.