Lyell Collection
Journal of the Geological Society
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Deans, T.
Right arrow Articles by Roberts, B.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Journal of the Geological Society; 1984; v. 141; issue.3; p. 563-580;
DOI: 10.1144/gsjgs.141.3.0563
© 1984 Geological Society of London

Article

Carbonatite tuffs and lava clasts of the Tinderet foothills, western Kenya: a study of calcified natrocarbonatites

T. Deans & B. Roberts

Miocene 'limestones' around Tinderet, noted for their mammalian fossils, but recognized as in part carbonatitic, are now shown to be carbonatite tuffs and volcaniclastics. They contain ejectamenta of fenites, sövites and blocks and bombs of carbonatite lava which have quenched trachytoidal and flow-banded textures and consist largely (90%) of calcite, plus apatite and magnetite. The principal primary constituent is inferred to have been nyerereite (cf. the natrocarbonatite of Oldoinyo Lengai) now pseudomorphed by calcite, and accompanied by primary tabular calcite. Phase relations and other occurrences of such rocks are discussed. The tuffs comprise lithic and crystal lapilli, Pele's tear-drop and accretionary lapilli types.

The silicate content of the tuffs and bombs is remarkably low (c. 3%), and their eruption preceded major flows of nephelinitic agglomerates. We suggest this sequence followed simultaneous separation of immiscible silicate and natrocarbonatite magmas at depth, but the greater energy and mobility of the carbonatite enabled it to surface first. These pyroclastics (and one carbonatite plug) form an outpost of the Homa Bay petrographic province.




This article has been cited by other articles:


Home page
 Can MineralHome page
D. S. Barker and K. L. Milliken
CEMENTATION OF THE FOOTPRINT TUFF, LAETOLI, TANZANIA
Can Mineral, 2008; 46: 831 - 841.
[Abstract] [Full Text] [PDF]

Home page
 Can MineralHome page
J. Keller and A. N. Zaitsev
CALCIOCARBONATITE DYKES AT OLDOINYO LENGAI, TANZANIA: THE FATE OF NATROCARBONATITE
Can Mineral, 2006; 44: 857 - 876.
[Abstract] [Full Text] [PDF]

Home page
 Can MineralHome page
R. H. Mitchell
CARBONATITES AND CARBONATITES AND CARBONATITES
Can Mineral, 2005; 43: 2049 - 2068.
[Abstract] [Full Text] [PDF]

Home page
 Journal of the Geological SocietyHome page
E. A. BESTLAND and G. J. RETALLACK
Volcanically influenced calcareous palaeosols from the Miocene Kiahera Formation, Rusinga Island, Kenya
Journal of the Geological Society, 1993; 150: 293 - 310.
[Abstract] [PDF]

Home page
 Journal of the Geological SocietyHome page
E. A. BESTLAND
A Miocene Gilbert-type fan-delta from a volcanically influenced lacustrine basin, Rusinga Island, Lake Victoria, Kenya
Journal of the Geological Society, 1991; 148: 1067 - 1078.
[Abstract] [PDF]

Home page
 Journal of the Geological SocietyHome page
B. T. NGWENYA and D. K. BAILEY
Kaluwe carbonatite, Zambia: an alternative to natrocarbonatite
Journal of the Geological Society, 1990; 147: 213 - 216.
[Abstract] [PDF]

Home page
 ScienceHome page
M. Krafft, M. KRAFFT, and J. KELLER
Temperature Measurements in Carbonatite Lava Lakes and Flows from Oldoinyo Lengai, Tanzania
Science, 1989; 245: 168 - 170.
[Abstract] [PDF]

Home page
 Journal of the Geological SocietyHome page
D. C. TURNER
Volcanic carbonatites of the Kaluwe complex, Zambia
Journal of the Geological Society, 1988; 145: 95 - 106.
[Abstract] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
B. H. Baker
Tectonics and volcanism of the southern Kenya Rift Valley and its influence on rift sedimentation
Geological Society, London, Special Publications, 1986; 25: 45 - 57.
[Abstract] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
R. L. Hay
Role of tephra in the preservation of fossils in Cenozoic deposits of East Africa
Geological Society, London, Special Publications, 1986; 25: 339 - 344.
[Abstract] [PDF]