Montana · Stillwater County
Past Producer

Benbow Mine

Stillwater County, Montana, United States
ChromiumPlatinumPalladiumRhodium
⌖ Show on mapUSGS source ↗
Commodities
PrimaryChromium
TertiaryPlatinum, Palladium, Rhodium
Commodity typeM
Deposit
Model2: Bushveld Cr
Deposit sizeS
WorkingsUnderground
Orebody formMASSIVE BANDS AND DISSEMINATED
Ore controlCrystal Settling In Large Magma Chamber
Materials
Ore mineralsChromite
GangueOlivine, Serpentine
Geology
Host rockHarzburgite
Associated rockQuartz Monzonite,Mafic Intrusive Rock · Stillwater Complex, Ultramafic Series
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) ; Reg.Trends: Strike Of Ultramafic Zone: N60 Deg. W-N 80 Deg.W, Numerous Small Faults Striking Northward
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
AlterationSome Serpentinization Of Harzburgite
Economic & production
Development statusPast Producer
First production1941
Discovery year1905
Identification
Deposit ID10042346
MRDS IDM060101
RegionNA
Data scoreA
Coordinates45.36436, -109.8069
References
WIMMLER, N.L., 1948, INVESTIGATION OF CHROMITE DEPOSITS OF THE STILLWATER COMPLEX, STILLWATER AND SWEETGRASS COUNTIES, MONT.: U.S. BUREAU OF MINES REPORT OF INVESTIGATIONS 4368, P. 16-19.PEOPLES, J.W., AND HOWLAND, A.L., 1940, CHROMITE DEPOSITS OF THE EASTERN PART OF THE STILLWATER COMPLEX, STILLWATER COUNTY, MONTANA: U.S. GEOLOGICAL SURVEY BULLETIN 922-N, P. 371-411.JACKSON, E.D., 1968, THE CHROMITE DEPOSITS OF THE STILLWATER COMPLEX, MONTANA, IN RIDGE, J.D., ED., ORE DEPOSITS OF THE UNITED STATES,1933/1967, GRATON-SALES VOLUME: NEW YORK, AMERICAN INSTITUTE OF MINING, METALLURGICAL, AND PETROLEUM ENGINEERS, P. 1495-1510.PAGE, N.J, RILEY, L.B., AND HAFFTY, JOSEPH, 1969, PLATINUM, PALLADIUM, AND RHODIUM ANALYSES OF ULTRAMAFIC AND MAFIC ROCKS FROM THE STILLWATER COMPLEX, NMONTANA: U.S. GEOLOGICAL SURVEY CIRCULAR 624, 12 P.PAGE, N.J, RILEY, L.B., AND HAFFTY, JOSEPH, 1972, VERTICAL AND LATERAL VARIATION OF PLATINUM, PALLADIUM, AND RHODIUM IN THE STILLWATER COMPLEX, MONTANA: ECONOMIC GEOLOGY, V. 67, P. 918.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, AND DOHRENWEND, J.C., 1973, MINERAL RESOURCE POTENTIAL OF THE STILLWATER COMPLEX AND ADJACENT ROCKS IN THE NORTHERN PART OF THE MOUNT WOOD AND MOUNT DOUGLAS QUADRANGLES, SOUTHWESTERN MONTANA: U.S. GEOLOGICAL SURVY CIRCULAR 684, 9 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. 1065-1068.1939 DIREXPL USBPAGE AND OTHERS, 1972