The Pan-African Kekem gabbro-norite (West-Cameroon), U–Pb zircon age, geochemistry and Sr–Nd isotopes: Geodynamical implication for the evolution of the Central African fold belt
作者： Maurice Kwékam , Pascal Affaton , Olivier Bruguier , Jean-Paul Liégeois , Gerald Hartmann
DOI: 10.1016/J.JAFREARSCI.2013.03.010
关键词: Massif 、 Zircon 、 Geology 、 Gabbro 、 Partial melting 、 Mantle (geology) 、 Craton 、 Norite 、 Geochemistry 、 Orogeny
摘要: The Kekem shoshonitic gabbro-norite association is part of the high-K calc-alkaline (HKCA) post-collisional magmatism, a major feature Pan-African Belt in Cameroon. LA-ICP-MS U-Pb zircon analyses provide an age 576 ± 4 Ma for complex. This interpreted as dating emplacement massif during waning stage orogeny. latter related to dextral movements along Central Cameroon Shear Zone (CCSZ). REE patterns display enriched LREE (LaN/YbN = 14.2-23.5) while HREE present nearly flat profile (DyN/YbN 1.3-1.7), and La/Sm Sm/Yb ratios led propose that gabbro-norites have been derived from partial melting garnet-spinel lherzolite mantle source. negative Nb-Ta Ti anomalies positive Pb indicate this source was modified by contribution subduction-related material. low Ce/Pb (2.6-10.4) Th/Yb associated high Ba/La ratios, enrichment could be slab fluids. As whole, geochemical features suggest primary gabbro-noritic magmas subduction-modified (metasomatised lithospheric mantle). Moderately 86Sr/87Sr initial (0.7068-0.7082), eNd (−5 −9) old Nd TDM model ages (1.6-1.8 Ga) are result contamination Neoproterozoic Paleoproterozoic crust. ca. CCSZ metacratonization northern margin Congo craton vertical planar delamination transcurrent faults, asthenospheric uprise mantle.
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