Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Sébastien Owona, Joseph Mvondo Ondoa, Marion Tichomirowa, Georges Emmanuel Ekodeck

The petrostructural characteristics and ²⁰⁷Pb/²⁰⁶Pb zircon data from the Ngomedzap-Akongo area (Nyong complex, SW-Cameroon)

Journal of Geosciences, volume 65 (2020), issue 3, 201 - 219

DOI: http://doi.org/10.3190/jgeosci.309

Herein, we constrain the Ngomedzap-Akongo geodynamic evolution in the eastern part of the Nyong complex (NyC) in SW Cameroon that belongs to the Paleoproterozoic West Central African Fold Belt (WCAF) through petrostructural field observations, laboratory analyses, and ²⁰⁷Pb/²⁰⁶Pb zircon geochronology. It consists of magnetite bearing quartzite, metagranodiorite, meta-anorthosite, metagabbro, and metasyenites that have recorded a polyphase D₁-D₃ deformation. D₁, likely a pure shear-type, has been strongly overprinted by the D₂ transpression flow regime that emplaced the Nyong tectonic nappe, transported top - to the East onto the Congo shield. This nappe is dissected by D₃ blastomylonitic shear-zones. Both the D₂ and D₃ have controlled the actual geometry of the Nyong belt, later crosscut by D₄ multiple brittle tectonic styles, likely post-orogenic. Zircon geochronology yielded ²⁰⁷Pb/²⁰⁶Pb zircon geochronology protolith Archean mean ages of 2764 ± 26 Ma (MSWD = 0.81) in metagranodiorite; 2816 ± 34 Ma (MSWD = 1.3) and 2789 ± 13 Ma (MSWD = 0.28) in metasyenites. These new data corroborate old ones and, together, document the Archean origin of the NyC as details of the Nyong fold-and-thrust belts that of WCAFB and South American homologous due to the colliding Congo-San Francisco shields associated with Eburnean/Trans Amazonian orogeny (2400-1800 Ma).