Evidence for a 2.06 Ga subduction at the western border of the Adamawa-Yade domain in Cameroon: Constraints from elemental geochemistry, zircon Hf isotopes and zircon U/Pb geochronology from Ititin metabasites

Abstract

The geodynamic significance of Adamawa Yade Domain in Cameroon is still highly debated. This paper presents mineralogical, geochemical, zircon U–Pb age and Hf isotopic data for NNE-trending garnet-bearing pyroxeno-amphibolite (GPAm) and amphibolite (Am) bodies exposed in the Ititin area located at the Northwestern border of the Adamawa-Yadé domain in Cameroon. The GPAm and Am were dated by SIMS U–Pb zircon methods and yielded upper and lower intercept ages of 2065 ± 30 Ma and 557 ± 29 Ma, and 2054 ± 40Ma and 803 ± 320Ma, respectively. In the primitive mantle-normalized trace elements pattern, the metabasites display spike-like pattern, with enrichment in Th and La, and depletion in Nb, Zr, Hf, P and Ti although lower abundances are recorded in GPAm. GPAm yielded 176 Hf/177Hf initial ratios (0.281243 to 0.281491) with ϵHf (2.06Ga) values of −9.7 to −0.7 whereas the Am display 176 Hf/177Hf initial ratios (0.281143–0.281206) with values of ϵHf (t) of −12.2 to9.8.Geochemistry and geochronological data suggest that GPAm and Am originated from a subduction - modified lithospheric mantle and were emplaced at 2.06 Ga in a continental arc setting during the Paleoproterozoic event that formed the West Central Africa Fold Belt. Both the GPAm and Am were subsequently overprinted by the Pan-African orogeny.