首页|Petrogenesis, tectonic setting and geodynamic implications of Ouaden, Doumba Bello, and Ngoura granitic plutons (Eastern Cameroon): Constraints from elemental and Sr-Nd—Hf isotopic data and zircon U-Pb ages
Petrogenesis, tectonic setting and geodynamic implications of Ouaden, Doumba Bello, and Ngoura granitic plutons (Eastern Cameroon): Constraints from elemental and Sr-Nd—Hf isotopic data and zircon U-Pb ages
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The Ouaden, Doumba Bello, and Ngoura granitic plutons, eastern Cameroon, comprise segments of the Central African Fold Belt (CAFB) situated along the northern edge of the Congo craton. A geochemical, isotopic and geochronological study was carried out on these three plutons to determine their petrogenesis and tectonic environment of formation. Granodiorites and granites (SiO2 of 65-73 wt%, Mg# of 14-46) of these plutons are potassic and weakly peraluminous with A/CNK ratios of 0.99-1.10. On primitive-mantle normalized trace element diagrams, all intrusives are depleted in Nb, Ta, and Ti. LA-ICP-MS zircon U-Pb dating indicate that the Ouaden, Doumba Bello and Ngoura granitic plutons were emplaced coevally at 640 ± 3 Ma, 641 ± 3 Ma, and 638 ± 4 Ma, respectively. The granodiorites and granites have variable 87Sr/86Sr(Q ratios of 0.71117-0.71831, relatively unradiogenic whole-rock eNd(t) values of-9.6 to-6.3, and zircon eHf(t) values ranging from-10.1 to-2.1; the occurrence of mafic microgranular enclaves suggests mixing with mantle-derived magmas, and such mixing possibly resulted in the scattering of zircon Hf data. Two-stage Nd-Hf model ages of 2115-1856 Ma and 2218-1708 Ma, and AFMQ of +5.3-+2.1 indicate that the studied granitoids were derived from partial melting of Paleoproterozoic crust under variable oxidizing conditions. All granitoids yield inherited zircon ages (736-685 Ma), indicating contamination of Early Neoproterozoic crust during ascent. A combined examination of the geological record, bulk rock chemistry and isotope signatures suggests that the granodiorites and granites formed by mixing of mantle-and crust-derived melts during a late-subduction early-collision setting between the Metacraton and the Congo craton.
Eastern CameroonNeoproterozoic granitoidssyn-collisionalSr-Nd-Hf isotopesZircon U-Pb dating
Yanick Brice Lemdjou、Huan Li、Scott A. Whattam
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Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
Department of Geosciences, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
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