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Scientific Investigations Report 2010–5070-H

Nickel-Cobalt Laterites—A Deposit Model

By Erin Marsh, Eric Anderson, and Floyd Gray

Chapter H of
Mineral Deposit Models for Resource Assessment

Thumbnail of and link to report PDF (6.19 MB)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.

First posted September 20, 2013

For additional information contact:
Director, Central Mineral and Environmental Resources Science Center
U.S. Geological Survey
Box 25046, MS-973
Denver Federal Center
Denver, CO 80225
http://minerals.cr.usgs.gov/

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Suggested citation:

Marsh, Erin, Anderson, Eric, and Gray, Floyd, 2013, Nickel-cobalt laterites—A deposit model, chap. H of Mineral deposit models for resource assessment: U.S. Geological Survey Scientific Investigations Report 2010–5070–H, 38 p., http://pubs.usgs.gov/sir/2010/5070/h/.



Contents

Abstract

Introduction

Deposit Type and Associated Commodities

Historical Evolution of Descriptive and Genetic Knowledge and Concepts

Regional Environment

Physical Description of Deposit

Geophysical Characteristics

Hypogene Ore Characteristics

Supergene Ore and Gangue Characteristics

Weathering/Supergene Processes

Geochemical Characteristics

Petrology of Associated Igneous Rocks

Petrology of Associated Sedimentary Rocks

Petrology of Associated Metamorphic Rocks

Theory of Deposit Formation

Exploration/Resource Assessment Guides

Geoenvironmental Features and Anthropogenic Mining Effects

Acknowledgments

References Cited


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