Distribution and Mobility of Platinum-Group Elements in the Late
Cretaceous Ni-laterite in the Northern Oman Mountains
Abstract
Low-grade Ni-laterite deposits are well-developed over the
mafic/ultramafic protoliths in the northern Oman Mountains.
Concentrations, distribution patterns and mobility of platinum-group
element (PGE) are investigated in some Ni-laterite profiles of the Oman
ophiolite as a possible unconventional PGE resource. The ultramafic
protolith displays the lowest PGE content (average total PGE = 35 ppb),
which is almost similar to the PGE content in the overlying saprolite
zone. The PGE content substantially increased upward in the laterite
profile, where the highest total PGE content (up to 253 ppb) is recorded
in the oxide and ferricrete/clay-rich zones. The highest PGE content
corresponds to Pt > Ru > Pd, while the lowest
PGE content is mostly corresponding to Os < Rh < Ir,
There is a general positive correlation between PGE contents and both
Cr2O3 and
Fe2O3 contents in the Ni-laterite
profiles. This may 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 and ferricrete/clay-rich zones
during the lateritization process. The PGE distribution patterns and
positive correlation with the ultramafic index of alteration (UMIA)
indicate that PGE can be mobilized in different proportions in the
surficial environment upon progressive lateritization processes. The
high concentration of total PGE in the Oman Ni-laterite is in good
agreement with the PGE-rich laterite deposits worldwide, which can be
considered as an unconventional PGE resource if adequate extraction and
refining processes can be applied for their recovery from the possible
upcoming Ni production.