| Basis for focus area |
The focus area includes U and radioactive mineral occurrences, including the large Schwartzwalder deposit (Wallace, 1982), located mainly in Precambrian gneiss along the Colorado Front Range, and approximately corresponds with a favorable area identified during the National Uranium Resource Evaluation program (U.S. Department of Energy, 1980). This area includes the Ralston Creek-Golden Gate and Idledale districts (Chenoweth, 1980). The geology is complex and the deposits may not all be of the same type sensu stricto, but are clustered into one focus area based on the similarity of the host rock and structural control of mineralization (Wallace, 1982; Wallace and Karlson, 1985). Focus area polygon was made by selecting structurally-controlled U-bearing mineral occurrences from the Colorado Radioactive Mineral Occurrences database (Nelson-Moore and others, 1978) and generating a 1 km buffer around the points. |
| Identified resources |
Identified resources of uranium; historical production of uranium. |
| Production |
The Schwartzwalder U deposit produced about 17 million lbs U3O8 between 1953 and 2000 (Pool, 2017). Twelve other mines in Jefferson county produced U, but only a small percentage compared to the Schwartzwalder’s total production. By 1971 these other mines had produced 39,781 tons of ore and 210,827 lbs U3O8 (Nelson-Moore and others, 1978). In Boulder County, the Fairday produced 20,934 tons containing 182,679 lbs U3O8, and the Victory produced 595 tons containing 1,908 lbs U3O8 (Nelson-Moore and others, 1978). |
| Status |
Past mining. |
| Estimated resources |
The Schwartzwalder mine has estimated resources of 16 million lbs of U3O8. |
| Geologic maps |
Tweto (1979), scale 1:500,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Proterozoic granite, quartzite, gneiss and schist. Uranium mineralization at the Schwartzwalder is within veins and breccia fillings along a major fault system in Precambrian metamorphic rocks (Nelson-Moore and others, 1978). In Jefferson County, seven of the ten mines occur where a fault or breccia zone transects the Precambrian Idaho Springs Formation. Nelson-Moore and others (1978) state, "with the exception of the Leyden Coal Mine, the Mann Ranch and the Pallaora Lease, these mines, including the Schwartzwalder, are all clustered along three northwest-trending faults or breccia reed systems within six miles of the fault system along the mountain front. |
| Deposits |
Jefferson County: Schwartzwalder mine (MRDS dep_id: 10107507), Ralston Buttes district, Golden Gate Canyon area, Ascension mine, Aubrey Ladwig Lease, Grapevine mine, Mann Ranch, Mena mine, Leyden Coal mine, Pallaora Leash, Stone Placer mine, Wright Lease. |
| Evidence from mineral occurrences |
MRDS; International Atomic Energy Agency (2020b); U.S. Environmental Protection Agency (2006). |
| Geochemical evidence |
No data. |
| Geophysical evidence |
No data. |
| Evidence from other sources |
No data. |
| Comments |
The Schwartzwalder mine is currently regulated under a mining reclamation permit issued by the Colorado Division of Reclamation Mining and Safety. They are currently treating groundwater. |
| Cover thickness and description |
Mineralization at the Schwartzwalder mine crops out and extends up to 2,500 ft. below the surface (Chenoweth, 1980). |
| Authors |
Susan Hall, Michael K. O'Keeffe, Joshua M. Rosera. |
| New data needs |
Geophysics, 1:24,000 scale geologic mapping of one quadrangle, digitization of existing 1:24,000 scale maps, possible compilation map. |
| Geologic mapping and modeling needs |
Most of this area has been mapped at 1:24,000 scale except for the Raymond quadrangle (the Allens Park quadrangle might be of interest also). There are numerous 1:24,000 scale maps here, not digitized, and 1:50,000 and 1:100,000 scale maps that cover area as well. Besides the two maps above, this could be more of a digitization and compilation project. |
| Geophysical survey and modeling needs |
High resolution Rank 1 aeromagnetic and aeroradiometric surveys needed. |
| Digital elevation data needs |
Lidar is adequate. |
