Description
Jack Nye, Jimmy And Jonas Hedges
Commodities
PrimaryNickel, Copper
SecondaryCobalt
TertiaryPGE, Silver, Gold
Commodity typeM
Deposit
Model1: Stillwater Ni-Cu
Deposit sizeN
WorkingsUnderground
Orebody formMASSIVE AND DISSEMINATED
Ore controlImmiscible Sulfide Liquid Enriched In Ni And Cu Exsolved From Mafic Silicate Magma And Accumulated Near Lower Contact Of The Stillwater Complex. Assimilation Of Sulfur From Rocks Adjacent To The Stillwater Complex May Have Led To The Exsolution Of The Sulfide Liquid (Zientek And Ripley, 1990)
Materials
Ore mineralsChalcopyrite, Pentlandite, Pyrrhotite
GangueMagnetite, Plagioclase
Geology
Host rockQuartz Monzonite,Peridotite,Hornfels
StructureThe Stillwater Complex Is Exposed Along The Northern Margin Of The Beartooth Uplift, One Of Several Laramide Basement-Cored Ranges That Make Up The Rocky Mountain Foreland Of South-Central Montana (Foose And Others, 1961: Kulik And Schmidt, 1988), Small Local Faults Of Minor Displacement
Tectonic settingTectonic Setting At Time Of Emplacement Of The Stillwater Complex Is Unknown. The Complex Was Emplaced Shortly After A Major Regional, Subduction-Related Magmatic Event That Culminated In Emplacement Of The 2.73-2.79 Ga Granitoid Suite In The Batholith Exposed In The Beartooth Uplift (Wooden And Others, 1991). However, There Is No Evidence That The Magmatism That Formed The Stillwater Complex Is Related To Convergent Margin Tectonics And Magmatism
AlterationNone Related To Ore-Forming Process
Economic & production
Development statusOccurrence
Discovery year1883
Identification
Deposit ID10095654
MRDS IDM060098
RegionNA
Data scoreB
Coordinates45.38575, -109.94885
References
ROBY, R.N., 1949, INVESTIGATION OF COPPER-NICKEL DEPOSITS OF THE STILLWATER COMPLEX, STILLWATER AND SWEETGRASS COUNTIES, MONT.: U.S. BUREAU OF MINES REPORT OF INVESTIGATIONS 4431, P. 10.ZIENTEK, M.L., 1993, MINERAL RESOURCE APPRAISAL FOR LOCATABLE MINERALS: THE STILLWATER COMPLEX, IN HAMMARSTROM, J.M., ZIENTEK, M.L., AND ELLIOTT, J.E., EDS., MINERAL RESOURCE ASSESSMENT OF THE ABSAROKA-BEARTOOTH STUDY AREA, CUSTER AND GALLATIN NATIONAL FORESTS, MONTANA: U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 93-207, P. F1-F83.PAGE, N.J, 1979, STILLWATER COMPLEX, MONTANA - STRUCTURE, MINERALOGY, AND PETROLOGY OF THE BASAL ZONE WITH EMPHASIS ON THE OCCURRENCE OF SULFIDES: U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1038, 69 P.PREMO, W.R., HELZ, R.T., ZIENTEK, M.L., AND LANGSTON, R.B., 1990, U-PB AND SM-ND AGES FOR THE STILLWATER COMPLEX AND ITS ASSOCIATED SILLS AND DIKES, BEARTOOTH MOUNTAINS, MONTANA: IDENTIFICATION OF A PARENT MAGMA?: GEOLOGY, V. 18, P. 1065-1068.ZIENTEK, M.L., AND RIPLEY, E.M., 1990, SULFUR ISOTOPIC STUDIES OF THE STILLWATER COMPLEX AND ASSOCIATED ROCKS, MONTANA: ECONOMIC GEOLOGY, V. 85, P. 376-391.