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Jeffrey C. Reid, Ph.D., P.G., CPG NC Geological Survey 919.733.2423 x403

Geologic and Geochemical Considerations for Radon in NC American Ground Water Trust meeting of April 5, 2002 Research Triangle Park, NC. Jeffrey C. Reid, Ph.D., P.G., CPG NC Geological Survey 919.733.2423 x403 http://www.geology.enr.state.nc.us.

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Jeffrey C. Reid, Ph.D., P.G., CPG NC Geological Survey 919.733.2423 x403

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  1. Geologic and Geochemical Considerations for Radon in NCAmerican Ground Water Trustmeeting of April 5, 2002Research Triangle Park, NC Jeffrey C. Reid, Ph.D., P.G., CPG NC Geological Survey 919.733.2423 x403 http://www.geology.enr.state.nc.us

  2. Geologic and Geochemical Considerations for Radon in NC • Geology • NC rocks with uranium • Regolith • Fracture systems (‘plumbing’) • Geochemistry • Summary • For further information

  3. Geology

  4. Uranium source rocks mineralogy and availability • Triassic sediments • ‘Granitic’ rocks and ‘pegmatites’ • Mineralogy is critical to understand uranium presence vs. availability • Zircon with uranium vs. clays • Heavy minerals (Fall Zone and monazite belts)

  5. 1985 Geologic Map of North Carolina NCGS, 1985

  6. Triassic – Cow Branch Formation

  7. Triassic – Cumnock Formation

  8. Spruce Pine pegmatite Spruce Pine pegmatites

  9. PPg granite – e.g. Sims

  10. Radon in the Sims pluton(Spear, 1993) • ~5.45 ppm U • 2,289 pC/l – rock • ~20,252 pC/l – groundwater

  11. Radon in the Rolesville pluton(Spear, 1993) • Soil permeability affected upward migration of radon • Rolesville granite median ~13,940pC/l • Raleigh gneiss ~979 pC/l • Limited number of samples

  12. Foliated to massive granite rock – Rolesville pluton

  13. Fracture systems The ‘plumbing system’

  14. Modified from Heath, 1984

  15. Modified from Heath, 1984

  16. Modified from LeGrand, 1967

  17. Other factors • Atmospheric changes • Pressure changes • Snow and rain • Etc. • Soil (type, structure, protolith, etc.) • Beyond the scope of today’s presentation • Fall into the emanometry field (soil gas) • Details of mineral chemistry availability

  18. Geochemistry

  19. Geochemistry • Uranium (U) • Potassium (K) • Thorium (Th) • Cerium (Ce)

  20. Heavy mineral sands

  21. Summary • Geology is important to understand uranium distribution • Mineralogy controls uranium distribution and availability • Fractures are the ‘plumbing system’ • Groundwater reflects the geochemistry

  22. Summary (continued) • Geochemistry • Uranium distribution is different for groundwater vs. stream sediments

  23. For further informationJeffrey C. Reid, Ph.D., P.G., CPGSenior Geologist – Minerals and Geographic Information Systems (GIS)NC Geological Survey1612 Mail Service CenterRaleigh, NC 27699-1612919.733.2423 x403e-mail: Jeff.Reid@ncmail.nethttp://www.geology.enr.state.nc.us

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