Some investigations of the roraima formation intrusives in British Guiana
By: Rust, B.R
.
Material type: 
ArticleDescription: 24-32p ; Illustration.Subject(s): Roraima formation - British Guiana - South America | Quartzitic - British Guiana - South America | Arkosic sandstones - British Guiana - South America
In:
Geological magazine : Vol. 100 Iss. 1-6 Year. 1963Summary: Abstract
A traverse of a noritic gabbro sill (c. 1,000 feet thick) intruding the Roraima Formation showed no cryptic layering, but small-scale fractionation throughout the sill is indicated by the strongly-zoned plagioclase (An80→40), and orthopyroxene (En79→54) with outer rims of inverted pigeonite. Olivine (Fo80) is only present in the chilled margin.
New evidence on the age of the granites underlying the Roraima Formation is given by the discovery of post-Roraima felsite dykes, with high-quartz phenocrysts.
| Item type | Current location | Collection | Call number | Status | Date due | Barcode |
|---|---|---|---|---|---|---|
Article
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Library and Information Centre Periodical Section | Bound Journal Collection | Not for loan | 002548_05 | ||
Serials/Scientific Journal
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Library and Information Centre Periodical Section | Bound Journal Collection | 550 GEO (Browse shelf) | Available | 002548 |
Abstract
A traverse of a noritic gabbro sill (c. 1,000 feet thick) intruding the Roraima Formation showed no cryptic layering, but small-scale fractionation throughout the sill is indicated by the strongly-zoned plagioclase (An80→40), and orthopyroxene (En79→54) with outer rims of inverted pigeonite. Olivine (Fo80) is only present in the chilled margin.
New evidence on the age of the granites underlying the Roraima Formation is given by the discovery of post-Roraima felsite dykes, with high-quartz phenocrysts.
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