Title: RMAG On The Rocks Field Trip: Uranium Deposits in the Fox Hills Sandstone, Weld County, Colorado
Event: OTR Field Trip
Event Date: April 24, 2010
Publication: The Outcrop, March 2010, p. 21
Uranium mineralization was first identified in Cretaceous-age sandstones in Weld County in the late 1960s. Large-scale exploration programs, by companies like Getty Oil, Mobil Oil and Union Pacific Railroad, followed in the 1970s. The major host rock of interest was the Fox Hills Sandstone, which was found to contain “roll front” uranium mineralization. similar to that being produced at the time in Wyoming basins.
The Fox Hills Sandstone in northeastern Colorado was deposited in a marginal marine environment, along the regressive shoreline of the retreating Cretaceous Seaway. Within this regressive sequence, the physical and chemical characteristics of the delta front and barrier island sands resulted in the formation of ideal host rocks. Uranium was later introduced into these host rocks from the unconformably overlying volcaniclastic sediments of the Oligocene-age White River Formation. Oxidized, uranium-bearing groundwater migrated downgradient from the source rocks into the favorable sands, where uranium was precipitated along geochemical (oxidation/ reduction) boundaries.
From 1974 to 1981, Rocky Mountain Energy Company (RMEC), the mining subsidiary of the Union Pacific Railroad (UPRR), completed over 3500 exploratory drill holes (one million feet of drilling) within the Fox Hills Sandstone along the western margin of the Cheyenne Basin, in Weld and Larimer Counties. This drilling delineated over 9.5 million pounds of uranium resources, with an average grade of 0.10% U308. RMEC had plans to mine some of these resources and haul the ore to their mine/mill complex in the Powder River Basin of Wyoming. Declining uranium prices in the 1980’s halted all production plans for this deposit.
Powertech (USA), Inc. purchased the UPRR mineral rights and the entire exploration database from Anadarko Petroleum in 2006. It is an excellent uranium deposit and most of the resources are well suited to in-situ recovery (ISR) technology. Powertech has initiated a State of Colorado mine permit application process and is currently conducting field studies to establish environmental baseline conditions at the site.
RMAG On-The-Rocks Field Trip: Powertech Denver Basin Uranium Project
April 24, 2010
Join us for an inside tour of Powertech Uranium’s uranium exploration activities in Weld County. The company has identified a major uranium deposit in sandstones of the Fox Hills formation of northern Colorado. The field trip will consist of three components:
1. The first portion of the field trip will involve a visit to Powertech’s office in Wellington, CO (approximately six miles from the project boundary). At the office. there will be a presentation on the depositional environment of the Fox Hills Sandstone in Northeastern Colorado, a discussion about the formation of epigenetic uranium deposits within these sands, a review of project-specific drill hole logs, core from the deposit and cross sections of the project area; and a discussion on the proposed in-situ recovery mining operation of the Centennial project.
2. The second portion of the field trip will involve examination of outcroppings of Fox Hills Sandstone in the area surrounding Wellington to further illustrate the marginal marine deposition system of this Upper Cretaceous formation.
3. The final portion of the field trip will involve a visit to the Centennial Project area and a discussion of past, current and planned field activities.
Wellington is approximately 1.5 hours north of Denver. It is estimated that the field trip will require five hours to complete.