Vanadium deposits in the Lower Permian Phosphoria Formation, Afton area, Lincoln County, western Wyoming

Abstract

Vanadium reserves are in the Phosphoria Formation of the Afton area, western Wyoming. The vanadium is in shale and mudstone beds in the Meade Peak Member of the Phosphoria Formation (Permian). Exploration work by the U.S.Geological Survey from the late 1930s to 1943 demonstrated that the vanadiferous zone is remarkably consistent in character, grade, thickness, and lateral continuity throughout the Afton and adjacent 1,000 square mile mountainous area. During the program of exploration and development, in cooperation with the U.S. Bureau of Mines, 123 trenches were dug across surface sections of the Meade Peak Member. Four shafts and six adits were driven into four lines of outcrop of the vanadiferous zone along Dry Creek. On the basis of these data, reserves of about 30 million tons of indicated vanadium ore averaging 1.1 percent V 2 O 5 are estimated. The richest central 2.1 feet of the vanadiferous zone is black shale, oolite, and dark-gray mudstone. The tonnage estimate is based in part on ore above main drainage levels and for an arbitrary 500 feet below drainage levels. Factors favorable to possible economic development of the vanadium deposits in the Afton area are the large indicated ore reserves and the topographically high areas above drainage levels. Unfavorable factors are the rough terrain, harsh climate, and narrow width of the ore bed. Nearby sources exist for coal, salt, and sulfur, which at the time of this study were necessary for processing the ore. This study demonstrates how a successful field exploration program can be completed under Spartan conditions, and a similar program to the north in the future could be immensely rewarding. About 1,000 square miles of similar mountainous terrain north of the Afton area contain many lines of Phosphoria outcrops that have not been explored adequately for vanadium, gold, silver, chromium, zinc, cadmium, and other trace elements known to be present.