Distribution and Mobility of Platinum-Group Elements in the Late
Cretaceous Ni-laterite Soil 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 highest PGE
contents (up to 253 ppb) in the Oman Ni-laterites are mainly
concentrated in the oxide/clay-rich zone of the laterite profiles. The
PGE contents are substantially decreased toward the saprolite and
underlying protoliths (average total PGE = 35 ppb). The highest PGE
content in the oxide zone is mostly corresponding to Pt >
Ru > Pd, while the lowest PGE content is mostly
corresponding to Os < Rh < Ir, which shows a general
positive trend of PGE distribution patterns. 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/clay-rich zone 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.