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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 63 (1979)

Issue: 4. (April)

First Page: 621

Last Page: 646

Title: Major Uranium Discovery in Volcaniclastic Sediments, Basin and Range Province, Yavapai County, Arizona

Author(s): J. E. Sherborne, Jr. (2), W. A. Buckovic (2), D. B. Dewitt (2), T. S. Hellinger (3), S. J. Pavlak (2)

Abstract:

The Anderson Mine uranium deposit in west-central Arizona is one of the first significant uranium discoveries in the Basin and Range province. The deposit occurs in gently dipping Miocene lacustrine sediments near the northeastern margin of the Date Creek basin. Mineralized units are primarily carbonaceous mudstones and siltstones interbedded with fine tuffaceous sedimentary rocks, freshwater marlstones and limestones, and a few thin sandstones. The sequence is underlain by Eocene(?) andesitic volcanic rocks and overlain by Miocene sedimentary rocks and basalt.

The uranium deposit has a tabular or blanket-type configuration with minimum dimensions of approximately 1,000 by 1,500 m. Mineralization extends at least 1,000 m farther downdip to the south. The mineralized zone is composed of several beds that are generally 1 to 3 m thick, but range up to 11 m. The mineralization is stacked in most areas and aggregate thicknesses greater than 15 m are common. Mineral grades range from 0.03 to 0.10% U3O8, with an average grade of approximately 0.07%. Molybdenum, sulfur, vanadium, and organic carbon are concentrated with the uranium mineralization. Other elements which are anomalous in much of the Anderson Mine strata include manganese, lithium, and fluorine. In parts of the orebody, there are variations in the disequilibrium fa tor; however, the overall factor is approximately 1.00.

The uranium-bearing tuffaceous sediments were deposited during periods of felsic volcanism in sheltered backwater areas marginal to an expanding Miocene lake. During subsequent compaction and dewatering of these uranium-rich lake sediments, the expelled alkaline fluids came in contact with strongly reducing paludal sediments causing the precipitation and fixation of uranium. Associated zeolitization, silicification, and argillic alteration indicate an early diagenetic origin for the primary coffinite(?) mineralization. Some remobilization and precipitation of uranium minerals in fractures have occurred in recent geologic time.

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