A Deposit Model for Carbonatite and Peralkaline Intrusion-Related Rare Earth Element Deposits Scientific Investigations Report 2010–5070–J U.S. Department of the Interior U.S. Geological Survey COVER. Photo 1. Sample of eudialyte (pink) within layered vein consisting of quartz, albite, and sodic amphibole, Dora Bay, Alaska. Size of sample is 11 by 9 cm. Photograph by Philip Verplanck, U.S. Geological Survey. Photo 2. Sample of coarse-grained, tabular bastnäsite within matrix of ferruginous dolomite, Birthday Claim, Mountain Pass, California. Size of sample is 16 by 9 cm. Photograph by Philip Verplanck, U.S. Geological Survey. A Deposit Model for Carbonatite and Peralkaline Intrusion-Related Rare Earth Element Deposits By Philip L. Verplanck, Bradley S. Van Gosen, Robert R. Seal, and Anne E. McCafferty Chapter J of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–J 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: 2014 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. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Verplanck, P.L., Van Gosen, B.S., Seal, R.R, and McCafferty, A.E., 2014, A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits: U.S. Geological Survey Scientific Investigations Report 2010–5070-J, 58 p., http://dx.doi.org/10.3133/sir20105070J. ISSN 2328-0328 (online) iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Alkaline Igneous Rocks........................................................................................................................4 The Rare Earth Elements .....................................................................................................................4 Purpose and Scope ..............................................................................................................................8 Deposit Type and Associated Commodities ..............................................................................................8 Name .......................................................................................................................................................8 Synonyms ...............................................................................................................................................8 Brief Description ...................................................................................................................................9 Associated and Transitional Deposit Types ...................................................................................11 Primary Commodities .........................................................................................................................11 Byproduct Commodities ....................................................................................................................12 Trace Constituents ..............................................................................................................................12 Example Deposits................................................................................................................................12 Historical Evolution of Descriptive and Genetic Knowledge and Concepts ......................................12 Regional Environment .................................................................................................................................13 Geotectonic Environment ..................................................................................................................13 Temporal (Secular) Relations ............................................................................................................13 Duration of Magmatic-Hydrothermal System and/or Mineralizing Processes ........................13 Relations to Structures ......................................................................................................................13 Relations to Igneous Rocks ...............................................................................................................13 Relations to Sedimentary Rocks ......................................................................................................15 Relations to Metamorphic Rocks .....................................................................................................15 Physical Description of Deposit ................................................................................................................15 Dimensions in Plan View ...................................................................................................................15 Size of Hydrothermal System Relative to Extent of Economically Mineralized Rock ..............17 Vertical Extent .....................................................................................................................................17 Form and Shape ..................................................................................................................................17 Host Rocks ...........................................................................................................................................17 Structural Setting(s) and Controls ...................................................................................................18 Remote Sensing ..................................................................................................................................18 Geophysical Characteristics ......................................................................................................................19 Radioactivity ........................................................................................................................................19 Magnetic Surveys ...............................................................................................................................20 Gravity Surveys ...................................................................................................................................21 Hypogene Ore Characteristics ..................................................................................................................22 Carbonatite Ore Characteristics–Mineralogy, Mineral Assemblages, and Paragenesis ......22 Peralkaline Intrusion-Related REE Deposits Ore Characteristics–Mineralogy, Mineral Assemblages, and Paragenesis .........................................................................................23 Hypogene Gangue Characteristics ...........................................................................................................23 Carbonatites—Mineralogy and Mineral Assemblages ...............................................................23 Peralkaline Hosted REE Deposits—Mineralogy and Mineral Assemblages ............................24 iv Hydrothermal Alteration .............................................................................................................................24 General Features.................................................................................................................................24 Hydrothermal Alteration Associated with Carbonatite REE Deposits .......................................24 Hydrothermal Alteration Associated with Peralkaline Intrusion-Related REE Deposits ........25 Weathering/Supergene Characteristics and Processes ......................................................................26 Mineralogical Reactions to Establish Process ..............................................................................26 Geochemical Processes ...................................................................................................................26 Effects of Micro and Macro Climates .............................................................................................27 Geochemical Characteristics ....................................................................................................................27 Trace Elements and Element Associations ....................................................................................27 Zoning Patterns ...................................................................................................................................30 Fluid Inclusion Geochemistry ...........................................................................................................30 Stable Isotope Geochemistry ...........................................................................................................31