The Columbia Supercontinent Broke up in the Ectasian MesoProterozoic

Mid-Mesoproterozoic (∼1.32 Ga) diabase swarms from the western Liaoning region in the northern margin of the North China Craton: Baddeleyite Pb–Pb geochronology, geochemistry and implications for the final breakup of the Columbia supercontinent

Authors:

Wang et al

Abstract:

Diabase swarms widely intrude the late Paleoproterozoic to Mesoproterozoic sedimentary rocks in the northern margin of the North China Craton (NCC). In this paper, we present new baddeleyite SIMS Pb–Pb ages and whole-rock geochemical data for representative samples of the diabase swarms intruding the Mesoproterozoic Wumishan and Xiamaling formations in the western Liaoning region. Our aim is to elucidate the age and origin of the diabase swarms and their relationship to the fragmentation of the Columbia supercontinent. The baddeleyite SIMS Pb–Pb dating results show emplacement ages varying from 1325.9 ± 4.1 Ma to 1318.6 ± 3.7 Ma, indicating voluminous basic magmatism leading to the generation of the diabase swarms during the Mid-Mesoproterozoic time. Geochemically, the Mesoproterozoic diabasic rocks have relatively low REEs contents and show weak positive Eu anomalies. Moreover, these diabase samples are characterized by enrichment in light rare earth elements (LREEs), large ion lithophile elements (LILEs; e.g., Rb and Pb) and some high field strength elements (HFSEs; e.g., Th, U, Zr, Ti and Hf), and depletion in heavy rare earth elements (HREEs) and several high field strength elements (HFSEs; e.g., Nb, Sm, Gd and P), with affinities to basalts belonging to within-plate tholeiite series. Taken together, these geochemical characteristics suggest that the primary magmas of the diabases in the western Liaoning region could have been derived by partial melting of a transitional mantle or slightly enriched mantle in a continental extensional setting. In the context of assembly, growth and breakup of the Columbia supercontinent, together with the recognition of large volumes of ∼1.32 Ga diabase swarms in the northern NCC as well as the nearly coeval rift-related anorogenic magmatism recorded elsewhere on the globe, such as Africa, Baltica, Siberia, North America and Greenland, we conclude that the northern margin of NCC experienced the global-scale Mid-Mesoproterozoic rifting events, corresponding to the final breakup of the Columbia supercontinent, probably at around 1.32 Ga.