File:Lamproite (Blue Ball Lamproite DIke, Early Cretaceous, ~106 Ma; Freedom Creek, near Blue Ball, Scott County, Arkansas, USA) (14636778568).jpg
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[edit]DescriptionLamproite (Blue Ball Lamproite DIke, Early Cretaceous, ~106 Ma; Freedom Creek, near Blue Ball, Scott County, Arkansas, USA) (14636778568).jpg |
Blue Ball Lamproite from the Blue Ball Lamproite Dike of western Arkansas, USA (3.0 cm across at its widest). 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. Kimberlites & lamproites 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 the Kimberley area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section. Lamproites have a cross-section more closely resembling that of a martini glass. Rocks of the Blue Ball Lamproite Dike (see sample above) consist of phlogopite and serpentinized olivine in a groundmass of mica, chromite, Ti-magnetite, perovskite, and carbonate. This dike intruded at about 106 million years (mid-Albian Stage, late Early Cretaceous). Locality: northern side of Freedom Creek, ~0.45 km northwest of the Freedom Creek-Dutch Creek intersection, south of Rt. 80, north of Dutch Creek Mountain (ridge), between the towns of Union Hill and Blue Ball, far-eastern Scott County, western Arkansas, USA (about 34° 56’ 14” North, 93° 45’ 33” West). |
Date | |
Source | Lamproite (Blue Ball Lamproite DIke, Early Cretaceous, ~106 Ma; Freedom Creek, near Blue Ball, Scott County, Arkansas, USA) |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14636778568 (archive). It was reviewed on 1 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
1 December 2019
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current | 09:05, 1 December 2019 | 829 × 749 (131 KB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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