Lady of the Lake mafic intrusive

Region West, Northwest
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

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.