Depositional Systems

Of Uranium in South Texas

William A. Ambrose

October 23, 2007

Bureau of Economic GeologyJohn A. and Katherine G. Jackson

School of Geosciences

Energy Minerals DivisionAmerican Association of

Petroleum Geologists

Acknowledgments

John Ames

Publication was authorized by the Director, Bureau of Economic Geology,The University of Texas at Austin

Jana Robinson

Joel Lardon

Lana Dieterich

Outline

Recent Uranium Production Trends

Play Elements-Source-Migration-Mineralization-Seal

Catahoula Formation

Oakville Sandstone

Summary

Bil

lio

n b

arr

els

oil

eq

uiv

ale

nt

yr-

1

Estimates of 21st centuryWorld energy suppliesBillion barrels oil equivalent

1900 2000 2100

Nuclear

U. S. Uranium Deposits

U3O8 reserves*, $85.00/lb.

Wyoming: 301New Mexico: 289AZ, CO, UT: 128Texas: 17

*million poundsSource: EIA (2006)

Spot Price, Sept. 24, 2007: $85.00/lb.(Ux Consulting Company, LLC)

Source: Uranium Industry Annual 2002

Yellowcake

www.stockinterview.com

BureauofEconomic

Geology QAd6136

U. S. Uranium Production

EIA (2007)

South Texas Uranium Trends

40 mi

GOM Tertiary Uranium-Bearing Units

Outline

Recent Uranium Production Trends

Play Elements-Source-Migration-Mineralization-Seal

Catahoula Formation

Oakville Sandstone

Summary

Modified fromGalloway (2007)

Oligocene Volcanic Source

Migration

OakvilleTransmissivity

Galloway, et al(1982)

QAd6142

Mineralization: Roll Front Genesis

Modified from Hobday and Galloway (1999)

BA

HematiticCore

U Mineralization

Power Resources, Inc. (2002)

Roll Front Outcrop

Seals and Semi-Confined Aquifers

Serve to concentrategroundwater flow intransmissive intervals

Promote effectiverecharge and dischargeof meteoric water

Modified from Henry et al. (1982)

Leaky seals along faultpromote upwardmigration of reducingfluids

Floodplain shalesand flooding surfaces

Simulated Fault

Outline

Recent Uranium Production Trends

Play Elements-Source-Migration-Mineralization-Seal

Catahoula Formation

Oakville Sandstone

Summary

CatahoulaPaleogeography

Modified from Galloway (1977)McGowen and Garner(1970)

Catahoula Net SandstoneSouth Texas

Modified from Galloway (1977)

BruniHoliday-El Mesquite

Detailed Map Area

Catahoula Sandstone GeometryNortheastern Duval County

Bruni and Holiday-El Mesquite

600,000 lb. resources0.070% grade (EIA, 2002)

B

B’

Modified from Galloway and Kaiser (1980)

5 mi

Bruni

Holiday-El Mesquite

Contours: Weight-percent Iron Sulfide

Limonite Dom. Marcasite Dom. Pyrite

B B’

Northwest Southeast

Bruni Roll Front

Modified from Goldhaber and Reynolds (1977)

Outline

Recent Uranium Production Trends

Play Elements-Source-Migration-Mineralization-Seal

Catahoula Formation

Oakville Sandstone

Summary

Oakville Fluvial DepocentersSouth Texas

VasquezRosita

Ray Point

George West

Modified from Galloway et al. (1982)

George West Uranium Mineralization

Modified fromGalloway et al. (1982)

Summary: Uranium Play Elementsin South Texas

Adequacy and ControlsPlay Element

SourceFelsic volcanic source adequatefor all Tertiary plays

MigrationPrimarily controlled bytransmissive depositional axes

MineralizationGeochemical gradients related toorganic facies changes, faults

SealImpacts zones of hydraulicconnectivity, transmissive zones