Ison Creek Kimberlite (Elliott County Peridotite, Late Cretaceous, 75 Ma; west of Stephens, Elliott County, Kentucky, USA) 12 : 無料・フリー素材/写真
Ison Creek Kimberlite (Elliott County Peridotite, Late Cretaceous, 75 Ma; west of Stephens, Elliott County, Kentucky, USA) 12 / 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 | Kimberlite in the Cretaceous of Kentucky, USA.Kimberlites and lamproites have tremendous economic importance because they are host rocks for gem-grade and industrial-grade diamonds. Kimberlites & lamproites are unusual igneous bodies having overall pipe-shaped geometries. Their mode of formation is only moderately understood because they have not been observed forming. They are known from scattered localities throughout the world - only some are significantly diamondiferous. Classic localities for diamonds are India and Brazil. Africa was also discovered to have many kimberlites and is world-famous for producing large numbers of diamonds. Other notable diamondiferous kimberlite-lamproite occurrences include Russia, China, northwestern Australia, and northwestern Canada. Kimberlites are named for the town of Kimberley, South Africa - several kimberlite pipes occur in that area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section, somewhat like a carrot. Lamproites have a cross-section shape that resembles a martini glass.The rock seen here has eroded from a poorly exposed, non-diamondiferous kimberlite intrusion in Kentucky called the Ison Creek Kimberlite (also known as the Ison Creek Pipe). South of this area is the Hamilton Branch Kimberlite (see: www.flickr.com/photos/jsjgeology/14637076989 ). Both are part of the so-called Elliott County Peridotite. The Ison Creek Kimberlite has olivine (some are serpentinized), perovskite, ilmenite, phlogopite mica (some are vermiculitized), pyrope garnet, bronzite orthopyroxene, chrome diopside, calcite, and pectolite. Documented xenoliths include Pennsylvanian Breathitt Formation black shale, limestone, basement granite fragments, and upper mantle eclogite fragments.Geologic unit: Ison Creek Kimberlite, Elliott County Peridotite, Campanian Stage, late Late Cretaceous, ~75 MaLocality: loose piece in unnamed north-flowing tributary gully south of Ison Creek, west of the town of Stephens, eastern Elliott County, northeastern Kentucky, USA (vicinity of 38° 07’ 41.95” North latitude, 82° 59’ 42.21" West longitude)---------------Info. at:www.mindat.org/loc-19435.html---------------Age info. from:Heaman et al. (2004) - The temporal evolution of North American kimberlites. Lithos 76: 377-397. |
| 撮影日 | 2011-10-21 16:36:46 |
| 撮影者 | James St. John |
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