Abstract: Geology and Exploration of Uravan Mineral Belt
John B. Hall, Anthony A. Kovschak
The existence of the Uravan mineral belt was postulated in 1943 by R. P. Fischer, but the discovery and mining of uranium-vanadium ores from the Salt Wash Sandstone Member of the Jurassic Morrison Formation actually date back to 1898. This narrow, elongate, arcuate belt outlines the largest and most productive Salt Wash ore deposits on the Colorado Plateau.
ERDA production records for the Uravan mineral belt show that a total of approximately 12,200,000 tons (10,980,000 MT) of ore averaging 1.33% V2O5 and 0.25% U3O8 have been produced through 1974.
The Salt Wash Sandstone Member is composed of fluvial sandstones and mudstones from an aggrading system of braided streams trending eastward, normal to the mineral belt, from an apex in south-central Utah. The sandstones typically form lenses commonly referred to as channels. The channels normally are in three stratigraphic zones, the uppermost being the most productive.
Criteria defining favorable areas for ore deposits are as follows: (1) sandstone thickness of at least 30 ft (9 m), (2) gray mudstone associated with the ore-bearing sandstone, (3) presence of carbonaceous material, and (4) character of sedimentary structures. Ore minerals were precipitated as mineralized solutions, migrating laterally, came in contact with reducing environments surrounding the carbonaceous matter.
Exploration today is confined to deep drilling from the surface, as most of the shallow or surface deposits have been mined. Exploratory drilling normally is done in three phases: (1) widely spaced drilling to delineate favorable channels, (2) moderately spaced drilling to locate ore, and (3) closely spaced drilling to block out any ore deposits. Exploration continues throughout the mining phase by the use of underground diamond drilling or percussion test-hole drilling to define further the location of ore.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC