In 1951 and 1952, the U.S. Geological Survey conducted a program of uranium investigations and geologic mapping in the Monument Valley area, Apache and Navajo Counties, Ariz. About 700 square miles were mapped on the Navajo Indian Reservation. A resource appraisal of the area was an inherent part of the program, and is detailed in this report.
Production of vanadium and uranium is from two areas, the Monument No. 1 mine area in Navajo County, and the Monument No. 2 mine area in Apache County. In the period 1942-53 about 200,300 tons of ore was produced from these two areas. This ore yielded about 1,700,000 pounds of U3O8 and about 6,500,000 pounds of V2O5. The grade ranged from 0.15 percent U3O8 to 0.60 percent U3O8, and from 0.38 percent V2O5 to 3.02 percent V2O5. The vanadium-uranium ratio is about 4:1.
The ore deposits are composed principally of the hydrous calcium-uranium vanadate tyuyamunite in basal channel sediments of the Shinarump member off the Chinle formation. Four types of ore bodies are present: (1) rods, (2) tabular ore bodies, (3) corvusite-type ore bodies, and (4) rolls.
The reserves of uranium- and vanadium-bearing material are classed as measured, indicated, inferred, and potential. The reserves are further divided into three grade classes for material 1 foot or more thick: (1) 0.10 percent U3O8 and 1.00 percent V2O5 and above; (2) 0.05 percent U3O8 and 0.50 percent V2O5 and less than 0.10 percent U3O8 and 1.00 percent V2O5; and (3) 0.01 percent U3O8 and 0.10 percent V2O5 and less than 0.05 percent U3O8 and 0.05 percent V2O5.
Measured reserves as of June 1953, in the Monument Valley area, Arizona, (all in the Monument No. 2 mine) total about 36,000 tons. Indicated reserves in the first grade class amount to about 62,000 tons. In this same grade class inferred reserves total about 3,000,000 tons. In the second grade class indicated and inferred reserves amount to about 2,000,000 tons. Inferred reserves in the third grade class total about 345,000 tons of mineralized material. Potential reserves in all grade classes for the Monument Valley area amount to about 13,000,000 tons.
It is recommended that an extensive exploration program be carried out in the Monument Valley area, Arizona. This program would consist of two phases. The first phase would involve a geophysical survey of selected channels and would have at its principal objective the delineation of the trend, length, width, and depth of scour of the channels. The second phase would consist of a diamond-drilling program that would make use of the data secured by the geophysical survey. This drilling program would have as one of its principal objectives the determination of which channels are most likely to contain ore bodies. Once the favorable channels are discovered, the drilling program could be carried on most suitably by private operators.