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Geochemistry and 40ar/39ar Geochronology of Amphibolites from Banefo-Mvoutsaha Area, Central Domain of the Pan-African Fold Belt in Cameroon

MVODO Hermine, NGA ESSOMBA TSOUNGUI Philomène Estelle, KOUANKAP NONO Gus Djibril, KAMGUIA WOGUIA Brice, SIMO Pascal

Journal of Geosciences and Geomatics. 2025, 13(2), 31-43 doi:10.12691/jgg-13-2-1
  • Figure 1. Geological reconstruction of African Panafrican domains and NE Brazil showing the continuity of the Sergipano Belt and North Equatorial Fold Belt [modified After 15,16,18,19]. ASZ: Adamawa shear zone; CCSZ: Central Cameroon Shear Zone; BOSZ: Bétaré-Oya shear zone; Pe: Pernambuco shear zone; Pa: Patos shear zone SF: Sanaga Fault; TBF: Tibati-Banyo Fault. Dash lines represent the boundary of Cameroon
  • Figure 2. Geological map of Cameroon with the three main domains of the Pan-African North-Equatorial Fold Belt [modified After 15], (1) southern domain corresponding to the Yaoundé series thrust on the Congo Craton, (2) central domain, (3) northern domain; granitoids suites are not further distinguished. CCSZ: Central Cameroon Shear Zone; DS: Dja series; NS: Nyong series; NT: Ntem complex; SF: Sanaga Fault; TBF: Tibati-Banyo Fault. Location of study area is marked by a star
  • Figure 3. Geological map of the Banefo-Mvoutsaha massif [modified after 12] showing sample locations
  • Figure 4. Photographs and micrographs of Banefo-Mvoutsaha amphibolites. A) Occurrence of massive amphibolites interbedded with migmatitic gneisses and garnet-bearing gneisses. B) heterogranular granolepidoblastic texture. Noted the orientation of the minerals and the presence of amphibole-fish. C) LPNA micrograph showing oriented amphibole, quart, garnet and pyroxene. D) LPA micrograph showing destabilization of pyroxene into brownish amphibole. E) Occurrence of banded amphibolites. Note the foliation. F) Granoblastic heterogranular texture. Quartz is rounded. Stocky and subhedral plagioclase crystals. G) LPNA micrograph showing a pile of biotite flake. H) LPA micrograph
  • Figure 5. A) Chondrite normalized REE distribution diagram for the Banefo-Mvoutsaha amphibolites. The normalizing chondrite values are from . B) Primitive mantle-normalized multi-element patterns. The normalizing chondrite values are from
  • Figure 6. Graphic representations of Ar-Ar data of massive amphibolites sample (T21G9): (A and B) patterns of cumulative 39Ar released %, (C and D) normal and inverse isochrons respectively)
  • Figure 7. Graphic representations of Ar-Ar data of banded amphibolites sample (T22A): (A and B) patterns of cumulative 39Ar released %, (C and D) normal and inverse isochrons respectively)
  • Figure 8. Geochemical classification diagrams of Banefo-Mvoutsaha amphibolites. A) Studied amphibolites position in the TiO2-Ni discriminating diagram for Ortho and para-amphibolites . B) Zr/TiO2/Ni plot diagram of metavolcanic rocks [from 36]. C) Zr/Ti vs. Nb/Y Plot of amphibolites protolites
  • Figure 9. K2O+Na2O vs. K2O/(K2O+Na2O) diagram of igneous rocks [adapted from 52] showing alteration trend of Bafoussam amphibolites
  • Figure 10. Discrimination diagrams showing the affinity of Banefo-Mvoutsaha amphibolites. A) FeOt/MgO vs. SiO2 Plot of . B) The AFM discrimination plot showing tholeiitic affinity of the Bafoussam amphibolites
  • Figure 11. Mg# vs. SiO2/Al2O3 diagram showing the primitive basalts field and differentiation and mineral fractionation trends (after )
  • Figure 12. Tectonic setting discrimination diagrams of the Banefo-Mvoutsaha amphibolites. A) Nb/Yb vs. Ba/Yb diagram (after ). B) Y vs. La/Nb diagram showing the distribution of the main amphibolites within back-arc basin basalts (BABB) field, (after ). C) La/Nb vs. Nb/Th tectonic discrimination diagram showing the plots of the Penjween amphibolites within arc field, (after )
  • Figure 13. (A) MgO-FeOT-Al2O3 plot after . B) CaO-Na2O-K2O ternary diagram showing sandstones compositions from oceanic Island Arc, Active Continental Margin tectonic settings
  • Figure 14. Geotectonic discrimination diagrams of the Banefo-Mvoutsaha amphibolites. A) Zr/Y vs Zr of indicating geotectonic context of studied amphibolites. B) Nb–Zr–Y of . WPA (AI, AII): Within-plate Alkalic Basalt; WPT (AII, C): Within-plate Tholeiitic Basalts; P MORB (B) plume mid-ocean ridge basalts; N MORB (D): normal mid-ocean ridge basalts; VAB (C, D): Volcanic Arc Basalts; WPB, Within-Plate Basalts; E-MORB, Enriched Mid-Ocean Ridge Basalts. C) Geotectonic diagram Th-Hf/3-Ta showing the positions of Banefo-Mvoutsaha amphibolites within the WPT/WPA domain