The vanadiferous zone of the Phosphoria Formation in western Wyoming and southeastern Idaho

Abstract

Abstract A black shale in the upper part of the Meade Peak Member of the Permian Phosphoria Formation contains an average of 0.8 to 0.9 percent V2O5 or more over a large area in western Wyoming and southeastern Idaho. In 1942 and 1943, this vanadiferous zone was sampled at numerous localities in the region by the U.S. Geological Survey, the Wyodak Coal and Manufacturing Co., and the U.S. Bureau of Mines. At Sublette Ridge, 1 mi east of the Idaho State line in Lincoln County, Wyoming, the vanadiferous zone lies about 50 ft below the top of the Meade Peak Member in the nearly vertical eastern limb of a north-striking anticline. The full thickness of the vanadiferous zone in the explored part of Sublette Ridge contains about 1.9 million tons of indicated subeconomic resources above drainage level. The richer upper part contains about 1.35 million tons. In the Paris-Bloomington area of Bear Lake County, Idaho, in the eastern foothills of the Bear River Range about I mi west of the towns of Paris and Bloomington, the Phosphoria Formation and associated rocks lie in the Paris syncline, which plunges about 15°N. The western limb of the syncline is overturned; the beds near the trough are nearly vertical, but, high on the limb, they dip as little as 20°W. The vanadiferous zone is about 35 ft below the top of the Meade Peak Member and about 5 ft below the upper phosphate zone. The zone consists of three beds: a shale, a phosphorite, and a siltstone, in ascending order. Estimates of measured, indicated, and inferred subeconomic resources of vanadium in the Paris-Bloomington area have been prepared for the shale bed, the shale and phosphorite beds combined, and the full thickness of the vanadiferous zone. Measured resources for the full zone are estimated to be 600,000 tons averaging 10.8 ft in thickness and 0.93 percent V2O5; indicated resources are 4,000,000 tons averaging 10 ft in thickness and 0.9 percent V2O5; inferred resources, within the area sampled, are 50 to 75 million tons averaging 10 ft in thickness and 0.6 to 1.0 percent V2O5. The vanadiferous zone appears to be the product of primary deposition from upwelling water in a reducing marine environment below wave base in a water depth of 100 m or so. These deposits formed on the outer continental shelf on the western side of the North American craton at low latitude, where deep, cold, nutrient-rich seawater came to the surface as a result of divergent upwelling in a tradewind belt. The vanadiferous zone in western Wyoming and southeastern Idaho contains about 41 million tons of indicated subeconomic resources averaging about 0.9 percent V2O5. Inferred resources are many times larger. Eventually, these inferred resources may prove to be an important source of vanadium and several other metals.