The geology and uranium-vanadium deposits of the San Rafael River mining area, Emery County, Utah (B-113)

By: L. M. Trimble and H. H. Doelling

The San Rafael River mining area, about 15 miles west of Green River, Utah, is important for its production of uranium and vanadium. The area is on the northeast flank of the San Rafael Swell south of the Uinta Basin and west of the Paradox fold and fault belt. Most of the mineralized areas are on the west flank of a broad, shallow trough adjacent to the east flank of the San Rafael Swell. The outcrops of the Entrada, Curtis, and Summerville formations are gently folded into anticlines, synclines and flexures whose axes trend northeastward. The upper Summerville is truncated beneath the fluvial Morrison. Continued folding created drainage channels in the Morrison that trend mostly to the northeast at about the same spacing as the Summerville folding. Superimposed across the west flank of the trough are numerous northwesterly trending faults, most with displacements of less than 50 feet, but a few reach 200 feet.

Uranium and vanadium mineralization is principally found in the uppermost thick channel system in the Salt Wash Member of the Morrison Formation. Carbonaceous material deposited in point-bar, levee, crevasse-splay, and channel-bottom environments appears to be the principal ore control. Most mineralization is aligned parallel to the northeasterly trending channels or gentle folds and flexures. Faulting cuts ore bodies and appears to be post-ore. The most common uranium and vanadium minerals include coffinite, uraninite, montroseite, and corvusite. At least 48 mines in the Tidwell and Acerson mineral belts have produced ore that yielded a total of about 3, I 00,000 pounds of uranium concentrate (U 3?8) and about 5,400,000 pounds of vanadium concentrate (V, Os) through 1975.

The area has a proven reserve of 23,000 tons at a 0.12 percent U3 0 8 grade with a potential of additional ore capable of yielding 8,000,000 pounds of uranium concentrate and a commensurate amount of vanadium concentrate. Smaller tonnages of higher grade material are available. The most favorable area for future prospecting lies in a band 2-1/2 miles wide extending southeastward from the Tidwell mineral belt.

Other Information:
Published: 1978
Pages: 122 p.
Plates: 4 pl.
Scale: 1:24,000
Location: Emery County
Media Type: Paper Publication