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Geochemistry of the Neoproterozoic Mbondo-Ngazi Tina Metasediments, Adamawa Area, Central Cameroon: Source Provenance and Tectonic Setting

Alexis Hamdja Ngoniri, Timoleon Ngnotue, Evine Laure Tanko Njiosseu, Patrick Ayonta Kenne, Sylvestre Ganno, Jean Paul Nzenti

Journal of Geosciences and Geomatics. 2020, 8(2), 94-109 doi:10.12691/jgg-8-2-5
  • Figure 1. (a) Geological sketch map of west-central and north-east Brasil with cratonic masses and the Pan-African-Brasiliano provinces belt in west-Gondawana; (b) Geological map of Cameroon showing the major lithotectonic domains. WCD: West Cameroon Domain, AYD: Adamawa-Yadé domain, YD: Yaoundé Domain, TBSZ: Tcholliré-Banyo shear zone, ASZ: Adamaoua shear zone, SSZ: Sanaga shear zone. Location of study area is marked by a red square
  • Figure 2. Geological sketch map of the Mbondo-Ngazi Tina area [32]
  • Figure 3. Photographs [outcrop (a, e, i) and hand specimen views (b, f, j)] and microphotographs (c, d, g, h, k, l) of the Mbondo-Ngazi Tina metsaediments. Abbreviations: Calc: Calcite; Chl: Chlorite; Ep: Epidote; Kfs: K-feldspar; Qtz: Quartz; Ms: Muscovite; Ser: sericite; Op: Opaque minerals
  • Figure 4. a) Zr/Ti vs Ni protolith discrimination diagram [34]; b) Sediment classification diagram [35]
  • Figure 5. Harker diagrams of selected major elements
  • Figure 6. Harker diagrams of selected trace elements
  • Figure 7. a, c and e: UCC-normalized multi-element patterns (normalizing values after [64]); b, d and f: PAAS-normalized REE patterns (normalizing values after [62])
  • Figure 8. Comparative chondrite-normalized REE patterns of Mbondo-Ngazi Tina rocks to UCC and PAAS
  • Figure 9. Molecular proportions of Al2O3–(Na2O + CaO*)–K2O ternary diagram [45] for the metasedimentary rocks of Mbondo-Ngazi Tina formations with Chemical Index of Alteration (CIA) scale
  • Figure 10. Plot of Th/U ratios vs. Th (a) and Th/Sc versus Zr/Sc(b) [46] Average source rock compositions are of Proterozoic age [44]. BAS, basalt; AND, andesite; GRA, granite; and PSS, Proterozoic sandstone
  • Figure 11. Source rocks discrimination diagram [56]. (a) K2O-Rb; (b) La/Th-Hf
  • Figure 12. (a) SiO2/Al2O3 vs. K2O/Na2O and (b) K2O/Na2O vs. SiO2 [59] for tectonic discrimination diagrams of the Mbondo-Ngazi Tina metsasedimentary rocks: A1 (arc setting, basaltic and andesitic detritus), and A2 (evolved arc setting, felsic–plutonic detritus), ARC (oceanic island-arc margin), ACM (active continental margin), PM (passive margin)
  • Figure 13. La vs. Th source rocks discriminating diagram for the metasedimentary rocks [62]