A Deposit Model for Magmatic Iron-Titanium-Oxide Deposits Related to Proterozoic Massif Anorthosite Plutonic Suites Scientific Investigations Report 2013–5091 U.S. Department of the Interior U.S. Geological Survey COVER. McIntyre mine located in the Adirondack State Park, New York (photo taken by Laurel G. Woodruff, U.S. Geological Survey). A Deposit Model for Magmatic Iron- Titanium-Oxide Deposits Related to Proterozoic Massif Anorthosite Plutonic Suites By Laurel G. Woodruff, Suzanne W. Nicholson, and David L. Fey Scientific Investigations Report 2013–5091 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia: 2013 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. 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Suggested citation: Woodruff, L.G., Nicholson, S.W., and Fey, D.L., 2013, A deposit model for magmatic iron-titanium-oxide deposits related to Proterozoic massif anorthosite plutonic suites: U.S. Geological Survey Scientific Investigations Report 2013–5091, 47 p., http://pubs.usgs.gov/sir/2013/5091/. iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Purpose and Scope ..............................................................................................................................3 Deposit Type and Related Commodities ....................................................................................................4 Name.... ...................................................................................................................................................4 Synonyms ...............................................................................................................................................4 Brief Description ...................................................................................................................................4 Associated and Transitional Deposit Types .....................................................................................7 Stratiform Mafic-Ultramafic Iron-Titanium-Vanadium Deposits ..........................................7 Nickel-Copper-Magmatic Sulfide Deposits .............................................................................8 Contact Metasomatic Rutile with Alkalic Anorthosite ..........................................................8 Heavy-Mineral Deposits .............................................................................................................8 Primary Commodities ...........................................................................................................................8 Byproduct Commodities ......................................................................................................................8 Example Deposits..................................................................................................................................9 Important Deposits ...............................................................................................................................9 Historical Evolution of Descriptive and Genetic Knowledge and Concepts ........................................9 Regional Environment .................................................................................................................................10 Geotectonic Environment and Magmatic Temporal Relations ....................................................10 Temporal (Secular) Relations of Oxides to Host Rocks ................................................................11 Relations to Structures ......................................................................................................................12 Relations to Igneous Rocks ...............................................................................................................12 Relations to Metamorphic Rocks .....................................................................................................12 Relations to Sedimentary Rocks ......................................................................................................12 Physical Description of Deposit ................................................................................................................12 Dimensions in Plan View ...................................................................................................................12 Size of Hydrothermal System Relative to Extent of Economically Mineralized Rock ..............14 Vertical Extent .....................................................................................................................................14 Form and Shape ..................................................................................................................................14 Host Rocks ...........................................................................................................................................14 Structural Setting(s) and Control .....................................................................................................15 Geophysical Characteristics ......................................................................................................................15 Magnetic Signatures ..........................................................................................................................15 Gravity Signatures ..............................................................................................................................16 Electrical Signatures ..........................................................................................................................16 Hypogene Ore Characteristics ..................................................................................................................16 Mineralogy and Mineral Assemblages ...........................................................................................16 Paragenesis .........................................................................................................................................17 Zoning Patterns ...................................................................................................................................19 Textures and Grain Size .....................................................................................................................20 Gangue Mineral Characteristics ...............................................................................................................20 Mineralogy and Mineral Assemblages ...........................................................................................20 Paragenesis .........................................................................................................................................21 iv Zoning Patterns ...................................................................................................................................21 Textures and Grain Sizes ...................................................................................................................21 Hydrothermal Alteration .............................................................................................................................22 Supergene Ore and Gangue Characteristics ..........................................................................................22 Weathering and Supergene Processes ...................................................................................................22 Geochemical Characteristics ....................................................................................................................22 Trace Elements and Element Associations ....................................................................................22 Zoning Patterns ...................................................................................................................................22 Isotope Geochemistry of Ores ..........................................................................................................23 Stable Isotope Geochemistry ..................................................................................................23 Radiogenic Isotope Geochemistry ..........................................................................................23 Petrology of Associated Igneous Rocks ..................................................................................................23 Rock Names .........................................................................................................................................24