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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Tack, L., Thomas, M., Wingate, M., Liegeois, J.P., Fernandez-Alonso, M. & Deblond, A. 2004. ‘Early Neoproterozoic magmatism (1000-910Ma) of the Zadinian and Mayumbian Groups (Bas-Congo): onset of Rodinia rifting at the western edge of the Congo craton’. Precambrian Research 110: 277-306. (PR).
Article in a scientific Journal / Article in a Journal
New ion microprobe U-Pb zircon ages, as well as some geochemical and isotopic analyses, for key igneous unit~ within the central part of the West Congo belt are integrated with geological information to provide an updatec geological map (I: I 000 000 scale) and a synthetic type cross-section of the belt, as well as an updated lithostrati· graphic chart of the 'West Congo Supergroup'. Three Neoproterozoic units are recognised, from oldest to youngest the Zadinian, Mayumbian and West Congolian 'Groups'. Emplacement of early Zadinian peralkaline granites (Noqu massif, 999 ± 7 Ma) and rhyolites (Palabala) was accompanied by incipient rift sedimentation, corresponding to th( onset of transtensional rifting, preferentially in a transverse mega-shear setting along the margin of the Congo craton Subsequent upper Zadinian magmatism produced a thick (1600-2400 m) basaltic sequence (Gangila), which hai geochemical characteristics typical of continental flood basalts (CFBs). The Gangila basalts, associated with majo1 pull-apart rifting, were followed rapidly by the 3000-4000 m thick Mayumbian rhyolitic lavas, dated at 920 ± 8 M< at the base and 912 ± 7 Ma at the top. The felsic lavas are intruded by coeval high-level (micro)granites, whos( emplacement is dated at 924 ± 25 Ma (Mativa body) and at 917 ± 14 Ma (Bata Kimenga body) in the Lufu massif This voluminous bimodal magmatic province is similar to the Parana and Deccan provinces, and shares simila1 lithospheric sources. It corresponds to the initial, transtensional rifting stage along the western edge of the Cong< craton before Rodinia breakup. The early Neoproterozoic rocks of the West Congo Supergroup rest unconformabl~ on a ca. 2.1 Ga Palaeoproterozoic polycyclic basement (Kimezian Supergroup). No Mesoproterozoic events arc recorded in the area. Following the initial, transtensional early Neoproterozoic (ca. 1000-910 Ma) rifting stage Bas-Congo behaved as a passive margin of the Congo craton, as indicated by deposition of ca. 4000 m o Neoproterozoic (pre-Pan-African) platform sediments (lower part of West Congolian Group) preceding ca. 2000 m o Pan-African molasse-type sediments (upper part of West Congolian Group). In the late Neoproterozoic, durin1 Pan-Mrican assembly of Gondwanaland, the Bas-Congo passive margin, which was largely protected by thicl lithosphere of the Congo craton, collided with a western active margin to form the Brasiliano-Arayuai belt