Carbonated melilitites and calcitized alkalicarbonatites from homa mountain, western Kenya : A reinterpretation
By: Clarke, M.G.C
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Contributor(s): Roberts, B.
Material type: 
ArticleDescription: 683-692pp.Subject(s): Alkalic composition - Homa mountain - Kenya | Carbonatite | Melilitites | Miocene quaternary age | Ultramafic composition | Geology - Homa mountain complex - Kenya | Petrography
In:
Geological magazine : Vol. 123 Iss. 1-6 Year. 1986Summary: Homa Mountain is a well developed ijolite/carbonatite complex of Miocene to Quaternary age. Late stage olivine melilitite occurs as a satellite plug, parts of which show strong deuteric alteration to carbonate resulting in complete pseudomorphing of the melilite.
A second satellite centre exposes a grey carbonate tuff and accompanying dykes, all of which exhibit relic textures after an elongate, rectangular mineral also formerly believed to be melilite. Comparison with other recently described occurrences indicates however that the second centre erupted alkali-carbonatite and that the chief mineral originally present was nyerereite (Na2Ca(CO3)2). The field relationships and petrographic characters of both rock types are described and criteria are given which permit distinction between carbonated melilite and calcitized nyerereite. It is concluded that olivine melilitite and alkalicarbonatite are closely related in space and time.
| Item type | Current location | Collection | Call number | Status | Date due | Barcode |
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Article
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Library and Information Centre Periodical Section | Bound Journal Collection | Not for loan | 002533_143 | ||
Serials/Scientific Journal
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Library and Information Centre Periodical Section | Bound Journal Collection | 550 GEO (Browse shelf) | Available | 002533 |
Homa Mountain is a well developed ijolite/carbonatite complex of Miocene to Quaternary age. Late stage olivine melilitite occurs as a satellite plug, parts of which show strong deuteric alteration to carbonate resulting in complete pseudomorphing of the melilite.
A second satellite centre exposes a grey carbonate tuff and accompanying dykes, all of which exhibit relic textures after an elongate, rectangular mineral also formerly believed to be melilite. Comparison with other recently described occurrences indicates however that the second centre erupted alkali-carbonatite and that the chief mineral originally present was nyerereite (Na2Ca(CO3)2). The field relationships and petrographic characters of both rock types are described and criteria are given which permit distinction between carbonated melilite and calcitized nyerereite. It is concluded that olivine melilitite and alkalicarbonatite are closely related in space and time.
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