首页|Petrogenesis and tectonic implication of Neoproterozoic I-Type Granitoids and orthogneisses in the Goa-Mandja area, Central African Fold Belt (Cameroon)
Petrogenesis and tectonic implication of Neoproterozoic I-Type Granitoids and orthogneisses in the Goa-Mandja area, Central African Fold Belt (Cameroon)
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The geological evolution of the Central African Fold Belt (CAFB) remains debated. The granitoids, orthogneisses and granitic veins from the Goa-Mandja area (Adamawa-Yade domain) are considered to constrain this belt. These rocks are consistent with late-D2 regional emplacement and synchronous with the magmatism at ～600 Ma within the CAFB in Cameroon and its extension into northeastern Brazil, as the zircon U-Pb dating points to 603-598 Ma crystallization ages. Analytical data reveal slighdy elevated δ~(18)O_(zrn) (6.45-7.17‰) and δ~(18)O_(WR) (8.20-8.61 ‰), moderate to high SiO2 (59.70-77.23 wt%), low MgO (0.07-2.77 wt%), Cr (0.29-55.12 ppm), Ni (0.45-33.6 ppm), V (1.52-116.62 ppm) and Mg~# (0.02-0.36) contents, indicating crustal origin. The low to medium ~(87)Sr/~(86)Sri (0.703328-0.722670) and positive to negative ε_(Nd(t)) (+5.7 to -9.9), coupled with the diversity of Nd model ages (TDM2) support the heterogeneity of crustal protoliths. The high positive ε_(Nd(t)) (+5.7) of the granitic vein indicates derivation from juvenile Neoproterozoic (Nd-T_(DM2) at 854 Ma) crustal protolith. T_(DM2 (Nd)) and T_(DM2(Hf)) ages of 1188-2120 Ma and 2173-2480 Ma also suggest the involvement of Mesoproterozoic to Paleoproterozoic crustal protoliths. Samples show metaluminous to weakly peraluminous, high-K calc-alkaline to shoshonitic and I-type granitoid features and are similar with crustal rocks in regard to LILE (Rb, K) and LREE enrichments and HFSE (Nb, Ta, Ti) depletions. These combined features indicate slab subduction related setting for the magma generation. Slab subduction may have generated the heat necessary to provoke partial melting at the lower crustal level. Considering their position close to the Tchollire-Banyo Fault corridor, at the transition between the Adamawa-Yade and northern domains, the subduction derived features shown by the Goa-Mandja I-type granitoids could be related to the subduction of an old plate boundary during amalgamation of Gondwana. Therefore, the Goa-Mandja area records dominant magmatic accretion along the northern margin of the Congo craton (active margin) associated with a possible northwestern subduction.
Pan-African magmatismGoa-Mandja I-type granitoidsPetrogenesisCentral African Fold Belt
Bovari Syprien Yomeun、Wei Wang、Jean Pierre Tchouankoue
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State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
Department of Earth Sciences, University of Yaounde I, P.O. Box 812, Yaounde, Cameroon
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