Carmen Creek (Freeman) district, Idaho
The rocks underlying the Carmen Creek district are quartzite, quartzitic slate, and schist of Middle Proterozoic age intruded by the Cretaceous or Tertiary Carmen stock along the west slope of the Beaverhead Mountains. These rocks are covered in the valleys by tuffaceous Tertiary sediments and by Quaternary gravels. Lode deposits in the metasedimentary rocks are of two types: gold-quartz fissure fillings in quartzite (Oro Cache mine) and gold-copper replacement deposits along shear zones in schist (Carmen Creek mine). Sulfide minerals in the ore are pyrite, chalcopyrite, galena, and sphalerite; gold occurs with the sulfides. The Oro Cache mine, opened about 1897, is the only property of significance. More than 5,000 ounces of gold were probably produced in the decade following its discovery (Umpleby, 1913).
Eldorado (Bohannon, Whiapey Creek) district, Idaho.
The Eldorado district is underlain by Middle Proterozoic quartzite and schist of the Yellowjacket Formation and Lemhi Group. Along the Lemhi River valley are tuffaceous Tertiary sandstones and shales. Lode deposits in quartzite are fissure-filling quartz veins containing pyrite, chalcopyrite, galena, and, rarely, native gold. Placer mining along Bohannon Creek was more profitable than lode mining in the mountains; the three stream terrace levels along Bohannon Creek produced $350,000 in gold from 1895 to 1911 (Umpleby, 1913). The Ranger mine was probably the main lode mine. Development at the Ranger began about 1880, and production continued sporadically through the 1930’s. Most of the 1,872 ounces of gold and 6,916 ounces of silver credited to lode mines from the district came from the Ranger (Peters, 1980)
Eureka ( Salmn City, .Jessie Creek, Aurora, Rattlesnake, Iron Creek) district, Idaho
Sources of data Bedrock in the Salmon River Mountains and Lemhi Range is mostly quartzite of the Yellowjacket Formation that has been intruded by granite of Middle Proterozoic age and shallow intrusions of Eocene age. Adjacent valleys and lower mountain slopes are underlain by volcanic and sedimentary deposits of Eocene and younger age. Mineral deposits are mostly veins in quartzite, containing chiefly silver, lead, and gold, although the largest mine in the district, the Pope-Shenon, produced copper and silver. The Pope-Shenon produced at least 2.6 million pounds of copper, beginning in 1908 (Anderson, 1956). Numerous deposits of coal, sandstone, and bentonite near Salmon were mined for local use in the early 1900’s. Placer gold production has been small. Several small secondary uranium deposits are known in rhyolite and in carbonaceous sediments of Tertiary age. A copper-molybdenum porphyry prospect at the north end of the district (Bobcat Gulch prospect) has been explored by drilling Which began in 1970
Gibbonsville (Dahlonega) district, Idaho.
Bedrock consists of thick-bedded argillite and quartzite of the Lemhi and Missoula Groups and the Yellowjacket Formation, a few diorite sills and dikes, and minor Tertiary volcanic rocks. The Lemhi and Missoula Group rocks strike northwest and dip steeply northeast. Numerous steep faults trend north, northwest, and northeast. Ore deposits, chiefly gold lodes, occur in quartzite and argillite as narrow, east-trending veins that are broken by numerous faults. The primary vein minerals are auriferous pyrite and chalcopyrite in a gangue of quartz and local calcite. Many gold placer deposits near Gibbonsville have been extensively developed. Since its discovery in 1877, the district has produced more than $2 million in gold, most of which (an estimated 83,500 ounces) came from the A. D. & M. mine (Umpleby, 1913).
Kirtley Creek district, Idaho.
Quartzite and argillite of the Yellowjacket Formation, broken by thrust faults and north-and northwest-trending steep faults, occupy the highest parts of the Beaverhead Mountains. Tertiary sediments occupy the lower mountain slopes. Quaternary alluvium and terraces cut in tuffaceous Tertiary sediments were mined using hydraulic giant and dredge at times between 1890 and 1918. The district, at that time, was the most productive placer area in Idaho. About 26,000 ounces of gold were produced. Veins in Middle Proterozoic quartzites, worked ~ near the head of Kirtley Creek, contain pyrite, chalcopyrite, galena, and free gold in a quartz gangue (Koschmann and Bergendahl, 1968)
McDevitt district, Idaho .
The northern Lemhi Range and the west flank of the Beaverhead Mountains are composed of quartzitic rocks of the Yellowjacket Formation (Middle Proterozoic). The intervening Lemhi Valley is underlain by Tertiary volcanic and sedimentary rocks. Mineral deposits include auriferous copper vein and replacement deposits in shear zones cutting the quartzitic rocks, and northeast-striking thorite-bearing veins in quartzite on the northern outskirts of the Lemhi Pass thorium district (centered about 3 miles south of the Dillon quadrangle). The Harmony mine was the major copper producer.
North Fork (Fourth-of-Ju1y. Boy1e Creek districts) area. Idaho
The area is underlain by Middle Proterozoic quartzite, Tertiary sedimentary deposits, and part of the Carmen stock, a Cretaceous-Tertiary granodiorite. Ore deposits are mainly veins in quartzite containing base and precious metals in the form of sulfides. Production has been small.
Pratt Creek district, Idaho
Highly faulted quartzites of the Yellowjacket Formation form the highest mountain slopes, and Tertiary and Quaternary deposits mantle the lower slopes. Mineral deposits consist mainly of scattered gold prospects on quartz veins in quartzite, which contain pyrite, chalcopyrite, galena, and sphalerite. Production has been small.
Sandy Creek district, Idaho
Quartzite of the Yellowjacket Formation is cut locally by diorite dikes and granitic intrusions. Lode deposits, found in the metasedimentary rocks, are fissure fillings of quartz with variable amounts of pyrite, chalcopyrite, and galena. Gold occurs with the sulfides. The Goldstone mine, discovered in the early 1890’s, is the principal mine in the district. This mine produced most, if not all, of the 4,055 ounces of gold, 4,433 ounces of silver, 71,359 pounds of copper, and 166,179 pounds of lead credited to the district from 1901 through 1954 (Peters, 1980).
informazioni tratte da https://pubs.usgs.gov/imap/1803c/report.pdf
