Publications scientifiques
* (Auteur correspondant)
Franck K. Djokgoue Yonga
Abaitouin Guiswe
Results in Earth Sciences
The main aim of this paper is to examine the petrogenetic processes controlling the distribution of gold and platinum group elements (Au-PGEs). Au-PGE contents were measured using NiS fire assay combined with inductively coupled plasma mass spectrometry. The peridotites consist of olivine, pyroxene, spinel, and serpentine, displaying porphyroclastic texture that indicates mantle deformation. High concentrations of Ni, Cr, Cu, V, and Co coupled with low rare earth element (REE) abundances, are consistent with an upper mantle origin. Most lherzolites from the Adamawa Plateau (Tello, Addi, Mazele) show IPGEs (Os, Ir, Ru) enrichment relative to PPGEs (Pd, Pt, Rh), low Al 2 O 3 (<2 wt.%), and Au <1 ppb, which is consistent with their origin as low-degree partial melting residues of fertile continental mantle. In contrast, Darang lherzolites exhibit distinct signatures: negative LOI values, high Al 2 O 3 (up to 7.54 wt.%), low MgO (~35 wt.%), Cr# approaching 1, IPGE/PPGE <1, low ΣPGEs (~2.43 ppb), and elevated Au (up to 42.50 ppb). These differences indicate variable melting degrees and localized metasomatic overprinting. Partial melting appears to control the gross abundance of PGEs, whereas hydrothermal alteration is responsible for the redistribution and local remobilization of gold, particularly at the Darang site. The Adamawa Plateau thus records the heterogeneous lithospheric mantle beneath the Cameroon Volcanic Line. Moreover, this study demonstrates that combined petrographic and geochemical investigations of continental peridotites can provide a deeper, process-based understanding of Au and PGE behavior during mantle petrogenesis.
