Geochemistry and geochronology of the Proterozoic granitoids

Panafrican terranes in Cameroon are part of the central Africa fold belt (CAPFB) also known as mobile belt of central Africa. The northern region in Cameroon, in relation to the Congo craton, portrays characteristics of an active Neoproterozoic continental margin (i.e. with evidence for MP to HP metamorphism, widespread migmatisation and intensive plutonism, regional crustal-scale shear zones, etc). No suture defined by ophiolitic rocks has yet been observed; thus, the nature and the location of the boundaries of collided blocks are still in debate. Central Cameroon is considered as potential candidate to the location of a oceanic suture. This has led to the formulation of a number of geodynamic models of the belt, which are often divergent. The common feature of those models is that they integrate many areas, where geological data are absent or very scarce. Granitoids of central Cameroon belongs to a regional batholith (Adamawa-Yade batholith) and include diorites, tonalites, granodiorites and granites of various composition (pyroxene-amphibole-biotite granitoids, amphibole-biotite granitoids, biotite-muscovite granites). They form a calc-alkaline suite with characteristic of I- to S-type granitoids. Rb-Sr whole-rock and mineral ages of 500-600 Ma, crystallization ages of 62010 Ma and 60010 Ma (U-Pb on zircon) and emplacement date of 61527 and 5758 Ma ( Th-U-Pb on monazite) have been determine in granitoids, while Palaeoproterozoic ages (i.e. 2.1 Ga) have been determined for the hosting basement. The complex history of central Cameroon require the determination of 1) the age of granitoids and related deformational phases using in-situ LA-MC-ICP-MS U-Th-Pb dating on zircon and/or phosphates; 2) the source and the evolution process of the magma with major, traces and REE; 3) the isotopic characteristic of the granitoids (Sr, Nd); and the evolution of the crust and mantle over time using the Hf isotope. 24 months research stay at the Department of Lithospheric Research of the University of Vienna will allow to fulfill the objectives addressed in this project. This will be fundamental for boosting the local and regional development, enhancing the bilateral cooperation between Cameroon and Austria.

Panafrican terranes in Cameroon are part of the central Africa fold belt (CAPFB) also known as mobile belt of central Africa. The northern region in Cameroon, in relation to the Congo craton, portrays characteristics of an active Neoproterozoic continental margin (i.e. with evidence for MP to HP metamorphism, widespread migmatisation and intensive plutonism, regional crustal-scale shear zones, etc). No suture defined by ophiolitic rocks has yet been observed; thus, the nature and the location of the boundaries of collided blocks are still in debate. Central Cameroon is considered as potential candidate to the location of a oceanic suture. This has led to the formulation of a number of geodynamic models of the belt, which are often divergent. The common feature of those models is that they integrate many areas, where geological data are absent or very scarce. Granitoids of central Cameroon belongs to a regional batholith (Adamawa-Yade batholith) and include diorites, tonalites, granodiorites and granites of various compositions (pyroxene-amphibole-biotite granitoids, amphibole-biotite granitoids, biotite-muscovite granites). They form a calc- alkaline suite with characteristic of I- to S-type granitoids. Rb-Sr whole-rock and mineral ages of 500-600 Ma, crystallization ages of 62010 Ma and 60010 Ma (U-Pb on zircon) and emplacement date of 61527 and 5758 Ma ( Th-U-Pb on monazite) have been determine in granitoids, while Palaeoproterozoic ages (i.e. 2.1 Ga) have been determined for the hosting basement. The complex history of central Cameroon require the determination of 1) the age of granitoids and related deformational phases using in-situ LA-MC-ICP-MS U-Th-Pb dating on zircon and/or phosphates; 2) the source and the evolution process of the magma with major, traces and REE; 3) the isotopic characteristic of the granitoids (Sr, Nd); and the evolution of the crust and mantle over time using the Hf isotope. 24 months research stay at the Department of Lithospheric Research of the University of Vienna will allow fulfilling the objectives addressed in this project. This will be fundamental for boosting the local and regional development, enhancing the bilateral cooperation between Cameroon and Austria. Internal zircon feature, LA-ICP-MS zircon U-Pb study and Th/U of the pyroxene-amphibole bearing gneiss of Central Cameroon (Meiganga area) strength one more the complexity of the regional geological history. CL characteristic allows to distinguishing three groups of zircon and one fragment of core, which define three distinct trends in a concordia diagram. These three trends represent the three sources of detritus (Meso Archean, Neo Archean and Paleo Proterozoic) which filled the sedimentary basin. Our results show that the Pre-Panafrican history of Central Cameroon includes Meso- to Neo- Archean crustal accretion and associated magmatism prior to the Paleoproterozoic event of West Central African Belt. Respect to this new insight, any evolutionary reconstruction of the area should integrate the presence of the Archean crust. Its location, extension and relationship with the Congo Craton to the south and the Saharan Meta Craton to the North represent the future challenge to be target.