Tactite skarn (Late Eocene, ~36 Ma; Star Tungsten Mine, Elko County, Nevada, USA) 3 : 無料・フリー素材/写真
Tactite skarn (Late Eocene, ~36 Ma; Star Tungsten Mine, Elko County, Nevada, USA) 3 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Skarn from the Eocene of Nevada, USA.Skarn is a contact metamorphic rock with a crystalline texture. It forms by heating and addition of elements (metasomatism) to country rocks in the immediate vicinity of an igneous intrusion (batholith, stock, sill, dike, laccolith). Carbonate rock skarn is frequently called "tactite". This example from Nevada's Harrison Pass Mining District has some scheelite and powellite. Scheelite is a calcium tungstate mineral, CaWO4. Powellite is a calcium molybdate mineral, CaMoO4. Tungsten-rich tactites at this site were mined in the 1940s and 1950s. Reported tungsten contents in the ore rocks range from about 0.5% to 2%. Minerals in the ore rocks include quartz, garnet, epidote, chlorite, calcite, scheelite, powellite, and sulfides.Geologic context: contact metamorphism of limestones of the Ordovician-aged Pogonip Formation along the southeastern portion of the Harrison Pass Stock / Pluton, a Late Eocene (~36 Ma) intrusion consisting of granite, granodiorite, and tonalite, plus aplite and mafic dikes. Locality: Star Tungsten Mine (Star Mine), Harrison Pass Mining District, south-southwest of the "town" of Ruby Valley, eastern side of the Ruby Range / Ruby Mountains, Elko County, northeastern Nevada, USA----------------------------Some info. from:Hess & Larsen (1922) - Contact-metamorphic tungsten deposits of the United States. United States Geological Survey Bulletin 725: 245-309.Smith (1976) - Mineral resources of Elko County, Nevada. United States Geological Survey Open-File Report 1976-56. 194+(7) pp. 1 pl.Barnes et al. (2001) - Petrology and geochemistry of the Late Eocene Harrison Pass Pluton, Ruby Mountains Core Complex, northeastern Nevada. Journal of Petrology 42: 901-929. |
| 撮影日 | 2025-03-19 17:45:08 |
| 撮影者 | James St. John |
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