| Basis for focus area |
Outline of mapped extent of the Cretaceous Lady of the Lake layered mafic intrusion at the southwest corner of the Tobacco Root batholith. |
| Identified resources |
None. |
| Production |
None. |
| Status |
Unknown. |
| Estimated resources |
Unknown. |
| Geologic maps |
Vuke and others (2014), scale 1:100,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Small lenses, pods, and stock-like bodies of metamorphosed and intensely altered harzburgite, lherzolite, and peridotite in the southern Tobacco Root Mountains. |
| Deposits |
None. |
| Evidence from mineral occurrences |
None. |
| Geochemical evidence |
Samples of small pods and lenses of ultramafic rocks from the northern part of the Tobacco Root Mountains were analyzed as part of a study of the Middle Mountain-Tobacco Root Roadless Area and they showed no significant concentrations of Co, Cu, Ni, Cr, or PGE (O'Neill and others, 1983). Platinum-group elements are known to occur in the Lady of the Lake Complex. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
The Lady of the Lake Complex in the southern part of the Tobacco Root Range (Horn and others, 1991, 1992), estimated to be about 1,000 Ma, intruded Archean quartzofeldspathic gneiss and is cut by the late Cretaceous Tobacco Root batholith (Horn and others, 1992). Its composition ranges from mafic norite and gabbro to granophyre. Precious metal concentrations of up to 1,300 ppb (gold + platinum + palladium) are reported in sulfide-rich zones of the complex (Horn and others, 1991). |
| Cover thickness and description |
Unknown. |
| Authors |
Stanley L. Korzeb, Kaleb C. Scarberry. |
| New data needs |
Geologic mapping, geophysics, lidar. |
| Geologic mapping and modeling needs |
Geologic mapping. |
| Geophysical survey and modeling needs |
High resolution airborne surveys where magmatic unconformities are suspected. |
| Digital elevation data needs |
Lidar inadequate. |
