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Nickel-Bearing Laterite Deposits in Accretionary Context

and the Case of New Caledonia: From the Large-Scale

Structure of Earth to Our Everyday Appliances

Pierre Maurizot*, Brice Sevin, Marion Iseppi, Geological Survey of New Caledonia (SGNC/DIMENC), BP 465, 98845,
Noumea, New Caledonia; Tanguy Giband, Mineral Authority (SMC/DIMENC), BP M2, 98849, Noumea, New Caledonia

ABSTRACT control nickel deposits is therefore crucial Ultramafic rocks are composed of silicate
Nickel production is vital to modern to industrial development. minerals, notably olivine, which are,
economic development. Of the different If one excludes polymetallic nodules of under wet and warm intertropical cli-
ore types, supergene Ni-laterite produc- the ocean floor, for which mining tech- mates, unstable and rapidly weathered
tion, as open-cast mining exploitation, nology and jurisdictional issues are still (Thorne et al., 2012; Wilson, 2004). Mg
is on the rise and surpassing the more not solved (Volkmann and Lehnen, 2017), and Si are released, whereas Fe, Al, Ni,
conventional hypogene sulfide type. This two main types of nickel deposits are and Co stay in situ. Consequently, a thick,
trend will likely continue. Assessing the known on land worldwide (Mudd and soft, residual cover of typical red- to
global resource of Ni laterite is therefore Jowitt, 2014): (i) hypogene magmatic yellow-colored Fe oxy-hydroxides accu-
of crucial importance. Compilation of nickel-sulfide deposits are found as lodes mulates, at times capped with ferricrete
scientific publications shows that the or layered complexes in ancient cratons (Fig. 2). Nickel is then concentrated up to
main producers and occurrences are and are mostly mined underground; and a grade of 1%–2% or even more (Butt,
concentrated in a few countries in South- (ii) supergene Ni-laterite deposits, which 2007; Freyssinet et al., 2005; Gleeson et
east Asia (New Caledonia, Indonesia, are formed by weathering of exposed al., 2003). This natural supergene process
the Philippines) and the Caribbean region ultramafic units, and as such are exploited of enrichment is very efficient with a
(Cuba and the Dominican Republic). In in open pits. second-enrichment factor of 10 times
these regions a common geological back- Supergene mineral deposits are low- compared to the initial ultramafic proto-
ground appears, characterized by large grade, large-tonnage resources, exploited lith and 200 times the average Earth crust
obducted ophiolites in tectonically active in easy surface conditions (ICMM, 2012). composition. Grades of Ni-laterite depos-
In the last decade, global production of Ni
its (0.8–15 wt% Ni) exceed that of mag-
settings, subject to weathering during the laterite has overtaken Ni sulfide (60% vs. matic Ni-sulfide deposits (0.5–5 wt% Ni;
Neogene. The neoformed mineralogy 40% according to Mudd and Jowitt, 2014), Arndt and Ganino, 2012). Cobalt is, in
of such surficial deposits is well docu- and the laterite proportion is still growing. some deposits, enriched in the same
mented. A model is proposed, based on Nickel-laterite deposits require ultra- proportion, but its initial and final con-
the knowledge gained on Ni-laterite mafic protoliths, such as Precambrian centrations are roughly 10 times lower.
deposits in New Caledonia, that could komatiites and layered complexes or In addition, recent studies about scan-
be applied to similar geological settings Phanerozoic ophiolites. Ophiolites corre- dium enrichment within Ni-Co laterites
worldwide. This model states that in spond to remnants of oceanic mantle and of New Caledonia show that Sc-bearing
accretionary terranes, vertical motions crust emplaced on land in collision zones goethites contain about 10 times the Sc
during weathering control both ore involving oceanic plates (Coleman, 1977). content of the parent rock (up to 100 ppm;
type and location. Mantle rocks are not commonly exposed Teitler et al., 2018).
at Earth’s surface and hence are restricted Scientific research on Ni-Co laterites,
INTRODUCTION to a few countries (Fig. 1). which present in essence a strong hetero-
Nickel-based alloys are used in many Typical mantle rocks have been geneity, is still low globally. New
applications, from modern information enriched, through repeated partial melt- Caledonia, a small French overseas
and communication technologies to large- ing and extraction episodes, in nickel up territory in the southwest Pacific, holds
scale industrial infrastructures, including to 0.18 wt%; i.e., 20 times the average ~25% of the global Ni-laterite resource
stainless-steel products used in our every- Earth crust concentration (Palme and (Berger et al., 2011; Mudd and Jowitt,
day life, such as coins, beer kegs, coffee O’Neill, 2014). However, economically, 2014). In terms of surface (18,500 km )
2
spoons, and much more. Improving this is not significant, and a secondary and population (~300,000), the archipel-
knowledge about geological factors that enrichment process has to take place. ago is certainly the smallest among the

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