Abstract
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.
Plain Language Summary
Laterite deposits are well‐developed over many igneous rocks called protoliths where an important geochemical process corresponding to intense weathering of those rocks and subsequent vertical redistribution of chemical elements along the weathering profile occurred particularly under tropical and subtropical conditions. Platinum‐group element (PGE) among other elements that are re‐concentrated during such geochemical processes. In this study, we look at the mobility and distribution patterns of PGE in some Ni‐laterite profiles of the Northern Oman ophiolite as a possible unconventional PGE resource. This study showed that the PGE range in concentration from about 35 ppb in the lower protolith and saprolite zones to about 253 ppb in the overlying oxide and ferricrete/clay‐rich zones of the laterite profile. PGE‐Cr2O3‐Fe2O3 relationship indicates that PGE‐Fe nanoparticle alloys are hosted by Fe‐rich oxyhydroxides or concentrated within the residual chromite grains. The high content of total PGE in the Oman Ni‐laterite is similar to many other PGE‐rich laterite deposits worldwide, which can be considered as an unconventional by‐products resource if adequate extraction and refining processes are applied for possible upcoming Ni production.
Key Points
Platinum‐group elements (PGE) can be mobilized in different proportions in the surficial environment
PGE might be hosted as nanoparticle within the oxy‐hydroxides minerals or as a residual accumulation of chromite in the oxide/clay‐rich zone
The high content of PGE can be considered as a by‐products resource if adequate extraction processes applied for possible future Ni mining