Distribution and Mobility of Platinum-Group Elements in the Late Cretaceous Ni-Laterite in the Northern Oman Mountains

Low-grade Ni-laterite deposits are irregularly developed overlying mafic/ultramafic protoliths in the northern Oman Mountains. Concentrations, distribution patterns, and mobility of platinum-group elements (PGEs) are investigated in some Ni-laterite profiles from the Oman ophiolite as potential unconventional PGE resource. The ultramafic protoliths display the lowest PGE contents (average total = 35 ppb) that are similar to the PGE contents in the overlying saprolite zones. The PGE content increased upward in the laterite profile, where the highest total PGE contents (∼253 ppb) are recorded in the oxide and ferricrete/clay-rich zones. The highest PGE content corresponds to Pt > Ru > Pd, while the lowest PGE content mostly corresponds to Os < Rh < Ir. The general positive correlation between PGE contents and both Cr₂O₃ and Fe₂O₃ contents and the positive trend of the chondrite-normalized PGE patterns in the Ni-laterite profiles reflect the formation of PGE-Fe nanoparticle alloys that are hosted by Fe-rich oxyhydroxides or due to the residual accumulation of chromite in the oxide/clay-rich zone during the lateritization process. The PGE distribution patterns and positive correlation of total PGE content with the ultramafic index of alteration indicate that PGE can be mobilized in different proportions in the surficial environment upon progressive lateritization processes. The high content of total PGE in the Oman Ni-laterite is in good agreement with PGE-rich laterite deposits worldwide. Consequently, the Oman deposits can be considered as an unconventional PGE resource if adequate extraction and refining processes are applied for their recovery from the possible upcoming Ni production.