Volcanogenic Uranium Deposits: Geology, Geochemical Processes, and Criteria for Resource Assessment By J. Thomas Nash Open-File Report 2010–1001 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2010 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Suggested citation: Nash, J. Thomas, 2010, Volcanogenic uranium deposits—Geology, geochemical processes, and criteria for resource assessment: U.S. Geological Survey Open-File Report 2010-1001, 99 p. 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 material contained within this report. Contents Abstract ...................................................................................................................... 1 Introduction ................................................................................................................ 2 Classification and Nomenclature............................................................................. 4 Known and Important Deposits: Descriptions and Comments ................................... 6 Largest in the World: Streltsovskoye, Russia ......................................................... 8 Even Larger “Volcanic” Deposit? Olympic Dam ...................................................... 9 Pocos de Caldas, Brazil ........................................................................................ 10 Dornot, Xiangshan, Chatkalo, and Other Districts of Asia ..................................... 12 Pena Blanca District, Mexico ................................................................................ 12 Macusani District, Peru ........................................................................................ 14 Lakeview District, Oregon ..................................................................................... 14 McDermitt District, Nevada and Oregon ............................................................... 17 Aurora Prospect, McDermitt, Nevada-Oregon ................................................... 17 Kings River area (Moonlight Mine) ..................................................................... 21 Marysvale District, Utah ........................................................................................ 22 Rexspar Deposit, Canada ..................................................................................... 23 Georgetown-Townsville Uranium Field, Australia ................................................. 23 Novazza, Italy ...................................................................................................... 26 Spor Mountain, Utah ............................................................................................. 26 Date Creek Basin, Arizona .................................................................................... 28 Lodeve District, France ......................................................................................... 30 Virgin Valley District, Nevada ................................................................................ 30 Deposits in Pre-Volcanic Structural Traps ............................................................... 31 Pitch Mine, Colorado ............................................................................................. 31 Midnite Mine, Washington ..................................................................................... 33 Apex Mine, Austin District, Nevada ....................................................................... 35 Arlit, Niger: Deposits in Volcaniclastic Sandstone ................................................. 36 Metamorphosed Volcanogenic Deposits ............................................................... 36 Genesis of Uranium Deposits: Concepts for Source, Transport, and Deposition ..... 37 Source Mechanisms and Concepts ...................................................................... 37 Uranium in Magmas and Magmatic-Hydrothermal Fluids .................................. 37 Rhyolite Magmatism .......................................................................................... 38 Petrochemistry of Uranium in Volcanic Rocks ................................................... 42 Release of Uranium .......................................................................................... 43 Transport Mechanisms and Concepts .................................................................. 44 Uranium Transport ............................................................................................. 44 Thorium Transport ............................................................................................. 45 Hydrology of Volcanic Systems.......................................................................... 46 Geochemical Signatures .................................................................................... 50 Uranium Deposition: Focused Flow, Traps, and Reductants ................................ 51 Post Ore: Preservation, Enrichment, or Destruction ................................................ 56 A Geologic Framework for Assessment ................................................................... 57 Assessment for Volcanogenic Uranium Deposits .................................................... 59 Introduction to Assessment Methods .................................................................... 59 iii Assessment Step 1: Permissive Tract Delineation ............................................... 59 Assessment Step 2: Grade and Tonnage Model ................................................. 60 Assessment Step 3A: Estimates of Number of Undiscovered Deposits ............... 61 Assessment Step 3B: Favorability Levels and Maps ............................................ 63 Quantitative Assessment Criteria .......................................................................... 64 Geology ............................................................................................................. 66 Geochemistry ..................................................................................................... 68 Geophysics ........................................................................................................ 68 Other Databases ................................................................................................ 69 Assessment Databases ........................................................................................ 70 Geology ............................................................................................................. 70 Geochemistry ..................................................................................................... 70 Geophysics ........................................................................................................ 71 Other Databases ................................................................................................ 72 Links to Other Assessments .............................................................................. 73 Suggestions for Further Work .................................................................................. 73 Comparison with Epithermal Processes ............................................................... 73 Refine Rhyolite Magmatism .................................................................................. 73 Evaluate Role of Sulfate-Rich Brines .................................................................... 74 Refine Sulfur Reduction Mechanisms ................................................................... 74 Hydrothermal Mobilization of Uranium in Volcaniclastic Strata ............................. 74 Refine Post-Ore Stability of Deposits ................................................................... 75 Refine Assessment Concepts and Practices ........................................................ 75 Concluding Remarks ................................................................................................ 76 Acknowledgments .................................................................................................... 77 References .............................................................................................................. 77 Appendix: Grade-Tonnage Relations Among Volcanogenic Uranium Deposits ...... 95 Figures 1. Location of volcanogenic uranium deposits, western U.S. ..................................... 7 2. Geologic map of the Streltsovskoye caldera, Russia ............................................. 9 3. Conceptual diagram of the phreatic stage, Olympic Dam deposit........................ 10 4. Cross sections, Pena Blanca .............................................................................. 13 5. Geologic map of the Lakeview District ................................................................ 16 6. Geologic map and section of the Aurora deposit ................................................. 19 7. Cross section showing geology and ore lenses, Aurora