Gneiss (Archean; Norris South roadcut, Madison County, Montana, USA) 6 : 無料・フリー素材/写真
Gneiss (Archean; Norris South roadcut, Madison County, Montana, USA) 6 / 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 | Gneiss in the Precambrian of Montana, USA.Gneiss is a high-grade, foliated metamorphic rock. It forms principally by metamorphism of schist, granite, or granite-like rocks. The foliation in gneiss is obvious and consists of alternating bands of light and dark minerals.Geologic unit & age: unit Agg of Kellogg (1994) - plagioclase-microcline-quartz-biotite gneiss, Archean, probably 3.1 to 3.2 Ga (= age of peak metamorphism during intrusion of Spanish Peaks area trondhjemites and tonalites)Locality: roadcut on the eastern side of Route 287, Burnt Creek-Bradley Creek Valley, south of the town of Norris, northern Madison County, southwestern Montana, USA (45° 31' 29.67" North latitude, 111° 41' 50.54" West longitude)------------------------------Reference cited:Kellogg (1994) - Geologic map of the Norris quadrangle, Madison County, Montana. United States Geological Survey Geologic Quadrangle Map GQ-1738. |
| 撮影日 | 2018-08-13 13:21:08 |
| 撮影者 | James St. John |
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