TY - JOUR
T1 - Nickel and cobalt distribution in the laterites of the Lomié region, south-east Cameroon
AU - Yongue-Fouateu, R.
AU - Ghogomu, R.T.
AU - Penaye, J.
AU - Ekodeck, G.E.
AU - Stendal, Henrik
AU - Colin, F.
N1 - Funding Information:
This work was supported by grants from ORSTOM (IRD: Institut Français de Recherche Scientifique pour le Développement en Coopération) and the “Métallogénie des roches basiques et ultrabasiques du Sud – Cameroun et de leur manteau d’altération: platinoı¨des et métaux stratégiques” Campus program for field work and stages of samples preparation and analysis. The authors are grateful to S.F. Toteu and J. Bennett for their helpful comments on the original manuscript. M. Economou-Eliopoulos and one anonymous reviewer have greatly contributed to the improvement of this manuscript; they are gratefully thanked. This work is a contribution to IGCP-470.
PY - 2006/5
Y1 - 2006/5
N2 - In the Lomié region (south-east Cameroon), strong weathering of serpentinized ultramafic rocks has produced a thick laterite cover with significant nickel and cobalt contents. The highest concentrations of these elements are located in the middle section of the laterite profiles, in the lower clay horizon, and preferentially along the slopes of the interfluves. The investigation of the composition of the laterite ores (by whole-rock analysis) and of the main components, using SEM/microprobe and XRD, reveals the presence of four main enriched facies: a non-differentiated facies, a layered smectitic facies, a quartz-rich facies and a gibbsitic nodular facies. Nickel, with generally low concentrations (less than 2% NiO), is hosted by several secondary mineral phases (goethite, Mn-oxyhydroxides and smectite locally). Cobalt is generally of higher grade (up to 0.9% CoO), and is associated with cryptocrystalline and crystallized Mn-oxyhydroxides. SEM/microprobe observations suggest that nickel and cobalt concentration in secondary minerals is due to repeated remobilization. This has also favored the formation of mineral phases, of which the best crystallized and most richly mineralized are mainly those of the asbolan-lithiophorite group. The SEM studies indicate that these mineral phases show various morphologies related to their chemical composition: poorly crystallized nipple shaped (Fe, Mn, Ni), fine cross-bedded needles (Mn, Ni) and elongated crystals (Mn, Al, Ni, Co) occur in the layered smectitic facies, while platy and needle-like forms (Mn, Al, Ni, Co) characterize the gibbsitic nodular facies. The predominantly cobaltiferous nature of the Lomié laterite ore deposit is the result of remobilizations and transformations of elements that led to the impoverishment of both the Ni-Co contents of the laterite but most importantly of Ni rather than Co.
AB - In the Lomié region (south-east Cameroon), strong weathering of serpentinized ultramafic rocks has produced a thick laterite cover with significant nickel and cobalt contents. The highest concentrations of these elements are located in the middle section of the laterite profiles, in the lower clay horizon, and preferentially along the slopes of the interfluves. The investigation of the composition of the laterite ores (by whole-rock analysis) and of the main components, using SEM/microprobe and XRD, reveals the presence of four main enriched facies: a non-differentiated facies, a layered smectitic facies, a quartz-rich facies and a gibbsitic nodular facies. Nickel, with generally low concentrations (less than 2% NiO), is hosted by several secondary mineral phases (goethite, Mn-oxyhydroxides and smectite locally). Cobalt is generally of higher grade (up to 0.9% CoO), and is associated with cryptocrystalline and crystallized Mn-oxyhydroxides. SEM/microprobe observations suggest that nickel and cobalt concentration in secondary minerals is due to repeated remobilization. This has also favored the formation of mineral phases, of which the best crystallized and most richly mineralized are mainly those of the asbolan-lithiophorite group. The SEM studies indicate that these mineral phases show various morphologies related to their chemical composition: poorly crystallized nipple shaped (Fe, Mn, Ni), fine cross-bedded needles (Mn, Ni) and elongated crystals (Mn, Al, Ni, Co) occur in the layered smectitic facies, while platy and needle-like forms (Mn, Al, Ni, Co) characterize the gibbsitic nodular facies. The predominantly cobaltiferous nature of the Lomié laterite ore deposit is the result of remobilizations and transformations of elements that led to the impoverishment of both the Ni-Co contents of the laterite but most importantly of Ni rather than Co.
KW - Cameroon
KW - Cobalt
KW - Laterites
KW - Manganese
KW - Nickel
KW - Serpentinite
UR - http://www.scopus.com/inward/record.url?scp=33646373904&partnerID=8YFLogxK
U2 - 10.1016/j.jafrearsci.2006.01.003
DO - 10.1016/j.jafrearsci.2006.01.003
M3 - Article
SN - 1464-343X
VL - 45
SP - 33
EP - 47
JO - Journal of African Earth Sciences
JF - Journal of African Earth Sciences
IS - 1
ER -