Composite hydrothermal vein (Emma Vein, 62-66 Ma; Butte, Montana, USA) 15 : 無料・フリー素材/写真
Composite hydrothermal vein (Emma Vein, 62-66 Ma; Butte, Montana, USA) 15 / 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 | The Emma Vein is a famous unit in the geology of Butte, Montana. The area’s country rocks are part of the Butte Quartz Monzonite (BQM), a Late Cretaceous-aged igneous intrusion that dates to 76 million years. The BQM is intruded by numerous hydrothermal veins that date to the latest Cretaceous-earliest Tertiary (~62 to 66 million years). Veins range from very thin to thick and are often composed of economically-significant minerals. The veins have been extensively mined, starting in the 1800s.At currently-existing outcrops, the Emma Vein is a 17 to 20 feet wide composite hydrothermal vein that is dominated by quartz, iron oxide, and manganese oxide. In the subsurface, the Emma Vein was reported to have chalcopyrite (CuFeS2, copper iron sulfide) and sphalerite (ZnS, zinc sulfide). At the eastern end of its subsurface occurrence, the Emma Vein was 100 feet wide and composed of nearly pure rhodochrosite (!).The BQM host rock is the light-colored material in the upper left portion of the outcrop.Geologic unit: Emma Vein, Maastrichtian Stage to Danian Stage, latest Cretaceous to Early Paleocene, ~62-66 MaLocality: outcrop on the northern side of a business at 800 West Platinum Street in the town of Butte, Silver Bow County, western Montana, USA |
| 撮影日 | 2010-08-09 15:53:03 |
| 撮影者 | James St. John |
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