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Open-File Report 2010–1179

Magmatic Sulfide-Rich Nickel-Copper Deposits Related to Picrite and (or) Tholeiitic Basalt Dike-Sill Complexes: A Preliminary Deposit Model

By Klaus J. Schulz1, Val W. Chandler2, Suzanne W. Nicholson1, Nadine Piatak1, Robert R. Seal, II1, Laurel G. Woodruff3, and Michael L. Zientek4

1 U.S. Geological Survey, 954 National Center, Reston, VA 20192
2 Minnesota Geological Survey, 2642 University Ave. W., St. Paul, MN 55114
3 U.S. Geological Survey, 2280 Woodale Dr., Mounds View, MN 55112
4 U.S. Geological Survey, West 904 Riverside Ave., Spokane, WA 99201

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Introduction

Magmatic sulfide deposits containing nickel (Ni) and copper (Cu), with or without (±) platinum-group elements (PGEs), account for approximately 60 percent of the world’s Ni production and are active exploration targets in the United States and elsewhere. On the basis of their principal metal production, magmatic sulfide deposits in mafic rocks can be divided into two major types: those that are sulfide-rich, typically with 10 to 90 percent sulfide minerals, and have economic value primarily because of their Ni and Cu contents; and those that are sulfide-poor, typically with 0.5 to 5 percent sulfide minerals, and are exploited principally for PGE. Because the purpose of this deposit model is to facilitate the assessment for undiscovered, potentially economic magmatic Ni-Cu±PGE sulfide deposits in the United States, it addresses only those deposits of economic significance that are likely to occur in the United States on the basis of known geology. Thus, this model focuses on deposits hosted by small- to medium-sized mafic and (or) ultramafic dikes and sills that are related to picrite and tholeiitic basalt magmatic systems generally emplaced in continental settings as a component of large igneous provinces (LIPs). World-class examples (those containing greater than 1 million tons Ni) of this deposit type include deposits at Noril’sk-Talnakh (Russia), Jinchuan (China), Pechenga (Russia), Voisey’s Bay (Canada), and Kabanga (Tanzania). In the United States, this deposit type is represented by the Eagle deposit in northern Michigan, currently under development by Kennecott Minerals.

First posted September 2010

For additional information contact:
Klaus Schulz
U.S. Geological Survey
12201 Sunrise Valley Drive
Reston, VA 20192

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Suggested citation:

Schulz, K.J., Chandler, V.W., Nicholson, S.W., Piatak, Nadine, Seall, II, R.R., Woodruff, L.G., and Zientek, M.L., 2010, Magmatic sulfide-rich nickel-copper deposits related to picrite and (or) tholeiitic basalt dike-sill complexes—A preliminary deposit model: U.S. Geological Survey Open-File Report 2010–1179, 25 p. (Available at http://pubs.usgs.gov/of/2010/1179/).



Contents

Introduction

Deposit Type and Related Deposits

Regional Environment

Physical Description of Deposit

Geophysical Characteristics

Hypogene and Supergene Ore Characteristics

Hypogene and Supergene Gangue Characteristics

Weathering - Supergene Processes

Geochemical Characteristics of Ores

Petrology of Related Igneous Rocks

Petrology of Related Sedimentary and Metamorphic Country Rocks

Theory of Deposit Formation

Exploration and Resource Assessment Guides

Regional geological guides

Local geological guides

Exploration methods

Geoenvironmental Features

References



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