Nickel-cobalt laterites: a deposit model: Chapter H in Mineral deposit models for resource assessment

Scientific Investigations Report 2010-5070- H
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Abstract

Nickel-cobalt (Ni-Co) laterite deposits are supergene
enrichments of Ni±Co that form from intense chemical and
mechanical weathering of ultramafic parent rocks. These
regolith deposits typically form within 26 degrees of the
equator, although there are a few exceptions. They form
in active continental margins and stable cratonic settings.
It takes as little as one million years for a laterite profile
to develop. Three subtypes of Ni-Co laterite deposits are
classified according to the dominant Ni-bearing mineralogy,
which include hydrous magnesium (Mg)-silicate, smectite,
and oxide. These minerals form in weathering horizons that
begin with the unweathered protolith at the base, saprolite
next, a smectite transition zone only in profiles where drainage
is very poor, followed by limonite, and then capped
with ferricrete at the top. The saprolite contains Ni-rich
hydrous Mg-silicates, the Ni-rich clays occur in the transition
horizon, and Ni-rich goethite occurs in the limonite.
Although these subtypes of deposits are the more widely
used terms for classification of Ni-Co laterite deposits, most
deposits have economic concentrations of Ni in more than
one horizon. Because of their complex mineralogy and heterogeneous
concentrations, mining of these metallurgically
complex deposits can be challenging. Deposits range in size
from 2.5 to about 400 million tonnes, with Ni and Co grades
of 0.66–2.4 percent (median 1.3) and 0.01–0.15 percent
(median 0.08), respectively. Modern techniques of ore delineation
and mineralogical identification are being developed
to aid in streamlining the Ni-Co laterite mining process, and
low-temperature and low-pressure ore processing techniques
are being tested that will treat the entire weathered profile.
There is evidence that the production of Ni and Co from
laterites is more energy intensive than that of sulfide ores,
reflecting the environmental impact of producing a Ni-Co
laterite deposit. Tailings may include high levels of magnesium,
sulfate, and manganese and have the potential to be
physically unstable.

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Nickel-cobalt laterites: a deposit model: Chapter H in Mineral deposit models for resource assessment
Series title Scientific Investigations Report
Series number 2010-5070
Chapter H
DOI 10.3133/sir20105070H
Year Published 2013
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Central Mineral and Environmental Resources Science Center, Geology, Geophysics, and Geochemistry Science Center
Description vii, 38 p.
Larger Work Type Report
Larger Work Subtype USGS Numbered Series
Larger Work Title Mineral deposit models for resource assessment (Scientific Investigations Report 2010-5070)
Online Only (Y/N) N
Additional Online Files (Y/N) N