Geology and History of the Smoky Mountains, Idaho
Paleozoic and Cretaceous rocks
The Smoky Mountains, west of the Big Wood River that runs through the valley towns of Ketchum, Hailey and Bellevue, contain upper Paleozoic sedimentary rocks of the Sun Valley Group which is mixed carbonate/siliciclastic strata (calcium carbonate marine organisms). This group contains the Wood River, Dollarhide, and Grand Prize Formations, intruded by the Cretaceous Idaho batholith and Eocene Challis granites. Wood River and Dollarhide Formations occur in the Smoky Mountains. Norton Peak has rocks probably from the Wood River Formation (sandy limestone, from what I have read). The Dollarhide Formation occurs in the southern Smoky Mountains. The Wood River Formation (Lower Permian to middle Pennsylvanian (300-250 Ma) includes siltstone and sandy limestone.
Paleozoic and Cretaceous rocks
The Smoky Mountains, west of the Big Wood River that runs through the valley towns of Ketchum, Hailey and Bellevue, contain upper Paleozoic sedimentary rocks of the Sun Valley Group which is mixed carbonate/siliciclastic strata (calcium carbonate marine organisms). This group contains the Wood River, Dollarhide, and Grand Prize Formations, intruded by the Cretaceous Idaho batholith and Eocene Challis granites. Wood River and Dollarhide Formations occur in the Smoky Mountains. Norton Peak has rocks probably from the Wood River Formation (sandy limestone, from what I have read). The Dollarhide Formation occurs in the southern Smoky Mountains. The Wood River Formation (Lower Permian to middle Pennsylvanian (300-250 Ma) includes siltstone and sandy limestone.
Sandy limestone with calcite crystals in rock found near Norton Peak summit, of the Sun Valley Group (Paleozoic).
Eocene intrusive rocks
Challis volcanic dacite ( a fine-grained, light colored igneous rock) lava flows make up much of the Smoky Mountains west of Hailey and northwest of Ketchum. Eocene intrusive (rocks that crystallize below the Earth's surface) granites seen in the Smoky Mountains include granodiorite and coarse-grained pink granites. Granodiorite contains a larger percentage of plagioclase feldspar than orthoclase feldspar compared to granite. Crustal extension occurred in Eocene (48 - 44 Ma) that created intrusive rocks and high-angle faults and ductile sheer zones and dike swarms (a major group of linear dikes intruded within continental crust).
Geological processes - faults and folds
During the Late Jurassic to Cretaceous Sevier mountain-building, crustal shortening occurred where older strata were folded, metamorphosed and thrust as the Atlanta Lobe of the Idaho Batholith intruded(100 - 75 Ma). Open, upright north-trending folds are present in the Smoky Mountains. Shortening was accommodated along the Pioneer thrust fault. A thrust fault occurs in response to lateral compression and therefore shortening, where the hanging wall is thrust up over the footwall, placing older rocks on top of younger rocks. Late Cretaceous granitoid rocks are exposed in the Smoky Mountains.
The eastern slopes of the Smoky Mountains are steeper than its western slopes because of block faulting causing the Big Wood River Valley to subside in relation to the Smoky and Boulder Mountain ranges.
Mineralization and Mining
The mountains of South-Central Idaho include mines that have ores created from the mineralization of Paleozoic rocks that were influenced by faults and folds formed during several mountain-building events. Intrusion of the Idaho Batholith created the most historically productive mineral deposits in the Wood River region, where Ketchum and Hailey reside. Faulting occurred during and after the batholith was intruded; this created veins filled with minerals from hydrothermal processes. In the southern Smoky Mountains, veins run parallel to the fold hinges. The Dollarhide Formation of the Sun Valley Group deposited during Permian and Pennsylvanian age is carbonaceous micritic siltstone which contains sheer-zone hosted veins in the mineralized areas of the Smoky Mountains.
Mineralization of Paleozoic rocks in the Smoky Mountains also occurred during Challis magmatism, Eocene time (48-44 Ma), during which granite and rhyolite intruded.
The Big Smoky fault strikes north through much of the Smoky Mountains.
The Rosetta mining district along the Big and Little Smoky Creeks, south of Norton Peak, had many mines, most of which were abandoned before 1900. Gold was produced here. Carrietown, a major mining area is ~ 13 miles directly south of Norton Peak and included in the Rosetta district. Ores rich in silver, lead and zinc were discovered in the Rosetta district in the 1880's. Mineralization of the Carrietown area occurred at 80 Ma during main Idaho Batholith intrusion into sedimentary rock of the Wood River formation (Paleozoic rock). In the Carrietown mineralized area, the host rock is limestone of the lower member of the Dollarhide Formation. Rocks created by geologic processes are: Paleozoic black shale, Cretaceous tonalite, Cretaceous granodiorite, and Eocene volcanic rock. Major structural features associated with the mineralization of rocks in Carrietown mines are northwest-and northeast-trending fracture systems on the east edge of the Idaho batholith. Cretaceous polymetallic veins (Wood River lead-silver veins) and Cretaceous polymetallic replacements had significant production of galena, sphalerite, pyrite. Ores occurred near contact of sedimentary rock with the batholith granitic rock. Ore minerals in the Dollarhide Formation, both in replacement and vein deposits, are galena, Sphalerite, tetrahedrite, pyrite, arsenopyrite, pyrrhotite, and chalcopyrite.
References:
Camas County Idaho Gold - Carrietown. IdahoGold.net
DeGray, Laura, and Paul Link of Idaho State University. The Digital Geology of Idaho - Challis Magmatic Episode
DeGray, Laura, Myles Miller and Paul K. Link. The Digital Geology of Idaho - Mesozoic Idaho Batholith
Geologic Map of Blaine County - The Digital Atlas of Idaho
Geology and Mineral Resources of the Hailey 1° X 2° Quadrangle and the Western Part of the Idaho Falls 1° X 2° Quadrangle, Idaho. (E Book).
Link, Paul Karl, Skipp, B., Hait Jr., M.H., Janecke, S., and Burton, B.R. Structural and Stratigraphic Transect of South-Central Idaho: A Field Guide to the Lost River, White Knob, Pioneer, Boulder, and Smoky Mountains (PDF).
Link, Paul K., Mahoney, J. Brian, Bruner, D., Batatian, L.D., Wilson, E., and Williams, F.J.C. Stratigraphic Setting of Sediment-Hosted Mineral Deposits in the Eastern Part of the Hailey 1° X 2° Quadrangle and Part of the Southern Part of the Challis 1° X 2° Quadrangle, South-Central Idaho.
Maley, T.S. 2019. Exploring Idaho Geology - Fourth Edition. Mineral Land Publications.
Rodgers, David W., Paul Karl Link, and Audrey D. Huerta. Structural Framework of Mineral Deposits Hosted by Paleozoic Rocks in the Northeastern part of the Hailey 1° x 2° Quadrangle, South-Central Idaho.
Challis volcanic dacite ( a fine-grained, light colored igneous rock) lava flows make up much of the Smoky Mountains west of Hailey and northwest of Ketchum. Eocene intrusive (rocks that crystallize below the Earth's surface) granites seen in the Smoky Mountains include granodiorite and coarse-grained pink granites. Granodiorite contains a larger percentage of plagioclase feldspar than orthoclase feldspar compared to granite. Crustal extension occurred in Eocene (48 - 44 Ma) that created intrusive rocks and high-angle faults and ductile sheer zones and dike swarms (a major group of linear dikes intruded within continental crust).
Geological processes - faults and folds
During the Late Jurassic to Cretaceous Sevier mountain-building, crustal shortening occurred where older strata were folded, metamorphosed and thrust as the Atlanta Lobe of the Idaho Batholith intruded(100 - 75 Ma). Open, upright north-trending folds are present in the Smoky Mountains. Shortening was accommodated along the Pioneer thrust fault. A thrust fault occurs in response to lateral compression and therefore shortening, where the hanging wall is thrust up over the footwall, placing older rocks on top of younger rocks. Late Cretaceous granitoid rocks are exposed in the Smoky Mountains.
The eastern slopes of the Smoky Mountains are steeper than its western slopes because of block faulting causing the Big Wood River Valley to subside in relation to the Smoky and Boulder Mountain ranges.
Mineralization and Mining
The mountains of South-Central Idaho include mines that have ores created from the mineralization of Paleozoic rocks that were influenced by faults and folds formed during several mountain-building events. Intrusion of the Idaho Batholith created the most historically productive mineral deposits in the Wood River region, where Ketchum and Hailey reside. Faulting occurred during and after the batholith was intruded; this created veins filled with minerals from hydrothermal processes. In the southern Smoky Mountains, veins run parallel to the fold hinges. The Dollarhide Formation of the Sun Valley Group deposited during Permian and Pennsylvanian age is carbonaceous micritic siltstone which contains sheer-zone hosted veins in the mineralized areas of the Smoky Mountains.
Mineralization of Paleozoic rocks in the Smoky Mountains also occurred during Challis magmatism, Eocene time (48-44 Ma), during which granite and rhyolite intruded.
The Big Smoky fault strikes north through much of the Smoky Mountains.
The Rosetta mining district along the Big and Little Smoky Creeks, south of Norton Peak, had many mines, most of which were abandoned before 1900. Gold was produced here. Carrietown, a major mining area is ~ 13 miles directly south of Norton Peak and included in the Rosetta district. Ores rich in silver, lead and zinc were discovered in the Rosetta district in the 1880's. Mineralization of the Carrietown area occurred at 80 Ma during main Idaho Batholith intrusion into sedimentary rock of the Wood River formation (Paleozoic rock). In the Carrietown mineralized area, the host rock is limestone of the lower member of the Dollarhide Formation. Rocks created by geologic processes are: Paleozoic black shale, Cretaceous tonalite, Cretaceous granodiorite, and Eocene volcanic rock. Major structural features associated with the mineralization of rocks in Carrietown mines are northwest-and northeast-trending fracture systems on the east edge of the Idaho batholith. Cretaceous polymetallic veins (Wood River lead-silver veins) and Cretaceous polymetallic replacements had significant production of galena, sphalerite, pyrite. Ores occurred near contact of sedimentary rock with the batholith granitic rock. Ore minerals in the Dollarhide Formation, both in replacement and vein deposits, are galena, Sphalerite, tetrahedrite, pyrite, arsenopyrite, pyrrhotite, and chalcopyrite.
References:
Camas County Idaho Gold - Carrietown. IdahoGold.net
DeGray, Laura, and Paul Link of Idaho State University. The Digital Geology of Idaho - Challis Magmatic Episode
DeGray, Laura, Myles Miller and Paul K. Link. The Digital Geology of Idaho - Mesozoic Idaho Batholith
Geologic Map of Blaine County - The Digital Atlas of Idaho
Geology and Mineral Resources of the Hailey 1° X 2° Quadrangle and the Western Part of the Idaho Falls 1° X 2° Quadrangle, Idaho. (E Book).
Link, Paul Karl, Skipp, B., Hait Jr., M.H., Janecke, S., and Burton, B.R. Structural and Stratigraphic Transect of South-Central Idaho: A Field Guide to the Lost River, White Knob, Pioneer, Boulder, and Smoky Mountains (PDF).
Link, Paul K., Mahoney, J. Brian, Bruner, D., Batatian, L.D., Wilson, E., and Williams, F.J.C. Stratigraphic Setting of Sediment-Hosted Mineral Deposits in the Eastern Part of the Hailey 1° X 2° Quadrangle and Part of the Southern Part of the Challis 1° X 2° Quadrangle, South-Central Idaho.
Maley, T.S. 2019. Exploring Idaho Geology - Fourth Edition. Mineral Land Publications.
Rodgers, David W., Paul Karl Link, and Audrey D. Huerta. Structural Framework of Mineral Deposits Hosted by Paleozoic Rocks in the Northeastern part of the Hailey 1° x 2° Quadrangle, South-Central Idaho.