| Basis for focus area |
Focus area is based on the outline of Proterozoic and Cambrian rock footprint in this area taken from the statewide geological map (Tweto, 1979). Focus area delineates Th and REE noted in veins, syenite dikes, fracture zones, and carbonatite dikes associated with three Cambrian alkaline complexes. Focus area also includes late Cambrian mafic plutonic complexes associated with Ti-Fe-V and Ni-Cu-PGE sulfide mineralization. |
| Identified resources |
Identified resources of iron, titanium, and vanadium. Historical production of copper, iron, nickel, silver, and titanium. |
| Production |
Iron Mountain mine produced 984.2 mt of ore with 48-50% Fe between 1872 and 1956 (used as iron ore and steel mill flux). In 1955 to 1956, ~34,447 mt of heavy aggregate (14% Ti metal, 18% Fe) was produced for use in underwater pipeline applications. Small amounts of Cu, Ni, and Ag were produced from the Gem mine in the 1800s. |
| Status |
Past mining. No apparent exploration activity is underway in this district as of 2010. Many of the prospective vein and fracture-zone deposits occur on private lands. There is currently exploration in the northeast portion of this property associated with a Broken-Hill type deposit in the Precambrian rocks. |
| Estimated resources |
Reserves at the Iron Mountain mine are small tonnage; remaining ore contains about 45 to 50% Fe, 0 to 14% TiO2, and 0.41 to 0.45% V2O5. |
| Geologic maps |
Scott and others (1978), scale 1:250,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Igneous anorthosite-norite layered structure in host rock accompanies and subparallels magnetite lenses. |
| Deposits |
Iron Mountain mine (MRDS dep_id: 10013539), Gem Park. |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
At the Iron Mountain mine, ilmenite-magnetite ore was mined, with waste rock consisting of olivine, sericite, and plagioclase. |
| Geophysical evidence |
Strong gradients in both regional gravity and magnetic data may indicate crustal boundaries that were involved in controlling mineralizing fluids that trend northeast north of Gem Park and McClure Mountain. |
| Evidence from other sources |
No data. |
| Comments |
Wet Mountain area footprint from USMIN and modified by the Colorado Geological Survey (CGS). CGS is currently compiling geochemistry results from this area in GIS. Additionally, CGS is digitizing existing geologic maps of this area. Note, this area overlaps other focus areas, including pegmatite districts and a potential deep porphyry system. Some other commodities (for example, fluorite) occur in the area, but may be associated with different mineral systems. As reported by the CGS, historical exploration at the Gem Park Complex (the furthest west intrusion) observed carbonatites, gabbro, REE-bearing minerals, fenitized rock, and magnetite bodies at depth. At least one of these drill holes extended to 1,438 feet below the ground surface. Logs of this hole indicate carbonatite veins with REE-bearing minerals down to the total depth (1,438 feet below ground surface [438 meters]); see Papson (1981). |
| Cover thickness and description |
The Cambrian (could also include Ordovician and younger) alkaline complexes outcrop at the surface and intrude Proterozoic metamorphic rocks and granite. Some areas have overlying Paleogene volcanic rocks as well as Quaternary cover. |
| Authors |
Ryan D. Taylor, Albert H. Hofstra, Joshua M. Rosera, V.J.S. (Tien) Grauch, Michael K. O'Keeffe. |
| New data needs |
1:24,000 scale geologic mapping, compilation geologic maps, geochemistry (historical data do not include full suites of critical minerals, REE, etc.), geophysical survey completed. |
| Geologic mapping and modeling needs |
The Colorado Geological Survey acquired funding to digitize 1:62.500 scale geologic maps through the USGS Data Preservation program. New 1:24,000 scale geologic mapping is required to fill in the patchwork of mostly 1:62,500/1:250,000 scale geologic mapping in the area. This would include mapping the Hardscrabble quadrangle and include completion of the partial 1:24,000 scale geologic mapping (see Sharp, 1978) of the Westcliffe, Aldrich Gulch, and Rosita quadrangles. Creation of a compilation geologic map at 1:50,000 scale using the existing 1:24,000/1:62,500 scale geologic maps, one new 1:24,000 scale geologic map of the Hardscrabble quadrangle, and three partial 1:24,000 scale geologic maps. Field work is required to check the compiled units, fix any edge-matching issues, and to verify the geology for three 1:10,000 scale insets for the Gem Park, McClure Mountain, and Democrat Creek complexes (some of these are already partially completed at 1:10,000 scale associated with USGS reports). |
| Geophysical survey and modeling needs |
Rank 1 aeromagnetic and radiometric data will provide insight into larger carbonatite, alkali, and mafic/ultramafic intrusions at depth. Acquisition of such a survey is underway for 2020-2021. (Wet Mountains survey). |
| Digital elevation data needs |
Lidar available. |
