The geology and production history of the uranium-vanadium deposits in the Lukachukai Mountains, Apache County, Arizona

Uranium-vanadium deposits have been discovered and mined in the Lukachukai Mountains, a high, rugged northwest spur of the Chuska Mountains in northeastern Arizona. All of the economic deposits are in the Salt Wash Member of the Morrison Formation of Jurassic age. Ore bodies occur some 30 to 80 feet above the base of the Salt Wash which is roughly the middle half of the member. All of the significant deposits are located in a well-defined belt which trends nearly north-south across the southeast end of the mountains. This belt accounts for 99.6 percent of the total production and includes an area of 6.5 square miles. The ore bodies are elongate and horizontally lenticular in shape and consist of one or more ore pods surrounded or separated by protore. The composite length of ore bodies consisting of two or more ore pods separated by protore ranges up to 1,100 feet; individual ore pods range up to 350 feet in length. The length is usually at least three times the width and is parallel to paleostream depositional trends measured in and near the ore bodies. Thicknesses of the ore bodies range from 1 to 22 feet. Claystone and/or siltstone beds nearly always underlie and frequently overlie the host sandstone units. Ore occurs most commonly in trough-type, cross-stratified sandstone which fills scours and channels in the underlying claystone. Lithofacies maps and mine mapping show that ore bodies are restricted to areas of rapid lateral color change which, in general, are also areas of rapid change in the ratio of mudstone to sandstone. It is common for the elongation of ore pods to deviate from the paleostream depositional trend and parallel the prominent joint set. This feature suggests some redistribution of the ore. (64 pages)Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu)