Partial melting of garnet bearing metabasite in the Nyong Complex (Southwestern Cameroon) records to the Eburnean/Trans-Amazonian orogenic: Evidence from field and petrological investigations
Authors: Ottou Eric José Messi , Aboula Yannick Saturnin Evina , Ntomba Sylvestre Martial , Ndjigui Paul-Désiré , Ondoa Joseph Mvondo 
Published: September 2023

AbstractField and petrographical inspections display that garnet bearing metabasite within Lolodorf area in the Nyong Complex was slightly melted during high P-T conditions of 9 to 11 kbar and 840 to 894 °C under very slightly wet melting conditions. Leucosome vein and pocket are present within garnet bearing metabasites. The leucosome veins within garnet bearing metabasites and garnet bearing leucogranite display the same peritectic minerals suggesting that they represent melt which compelled in the Nyong Complex. The garnet and clinopyroxene are inclusions rich which are interpreted as trapped melt, ribbon quartz within the leucosome body which represents injected melt combined with leucosome composed of peritectic products of garnet, clinopyroxene, (± amphibole) and the presence of coalesce garnet grains after dislocation of garnet necklace are consistent with anatexis. The metabasite of Lolodorf in the Nyong rocks archives the geodynamic of the of the Eburnean/Trans-Amazonian orogenic events. These field and petrographic observations are supported by chemical analyses, in which the enrichment of MB3 sample in K2O, Ba, LREE, Th, Hf, Zr, and P2O5than others garnet bearing metabasite samples. These results lead us to consider the Nyong Complex as a younger Complex resulted during Eburnean period. Partial melting of garnet bearing metabasite in the Nyong Complex highlights to stabilisation and differentiation of the Eburnean/Trans-Amazonian orogenic crust. Field and petrographical inspections display that garnet bearing metabasite within the Lolodorf area in the Nyong Complex was slightly melted during high P-T conditions of 9 to 11 kbar and 840 to 894 °C under very slightly wet melting conditions. Leucosome veins and pockets are present within garnet bearing metabasites. The leucosome veins within garnet bearing metabasites and garnet bearing leucogranite display the same peritectic minerals metabases suggesting that they represent melt which, compelled in the Nyong Complex. The garnet and clinopyroxene are rich inclusions which are interpreted as trapped melt, ribbon quartz within the leucosome body, which represents injected melt combined with the leucosome composed of peritectic products of garnet, clinopyroxene, (± amphibole) and the presence of coalesce garnet grains after dislocation of garnet necklace are consistent with anatexis. The metabasite of Lolodorf in the Nyong rocks geobics the geodynamics of the Eburnean/Trans-Amazonian orogenic events. These field and petrographic observations are supported by chemical analyses, in which the enrichment of MB3 samples in K2O, Ba, LREE, Th, Hf, Zr, and P2O5rather than other garnet bearing metabasite samples. These results lead us to consider the Nyong Complex as a younger Complex that resulted during the Eburnean period. Partial melting of garnet bearing metabasite in the Nyong Complex highlights to stabilisation and differentiation of the Eburnean/Trans-Amazonian orogenic crust.