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Carbonatite lapilli-bearing tuff and a dolomite carbonatite bomb from Murumuli crater, Katwe volcanic field, Uganda

Published online by Cambridge University Press:  05 July 2018

F. Stoppa ,
A. R. Woolley ,
F. E. Lloyd  and
N. Eby
F. Stoppa*
Affiliation:
Dipartimento di Scienze della Terra, Università G. d'Annunzio, 66013-Chieti Scalo, Italy
A. R. Woolley
Affiliation:
Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK
F. E. Lloyd
Affiliation:
PRIS, University of Reading, Whiteknights, Reading, RG6 6AB, UK
N. Eby
Affiliation:
Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, Lowell, MA 01854, USA
*
*E-mail: stoppa@phobos.unich.it
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Abstract

A group of carbonate-rich tuffs are described from the Murumuli crater, Katwe-Kikorongo volcanic field, SW Uganda which contain abundant carbonatite pelletal lapilli, together with melilitite lapilli and a range of xenocrysts and lithic fragments including clinopyroxenites considered to be of mantle origin. The carbonatite lapilli consist essentially of Sr-bearing calcite and Mg-calcite which form quench-textured laths. The lapilli contain microphenocrysts of Ti-magnetite, perovskite, apatite, clinopyroxene, sanidine and altered prisms of melilite. A 7 cm long dolomite carbonatite bomb is described which displays a form typically assumed by lava clots erupted in a molten state. Chemical analyses of a tuff, the bomb and a range of minerals are presented. Carbonatite clearly played an important role in the Katwe-Kikorongo magmatism and it is suggested that carbonatite magma evolved from carbonate-bearing melilitite.

Keywords

Katwe-KikorongoUgandacarbonatite lapillicarbonatite bombmelilitite
Type
Research Article
Information
Mineralogical Magazine , Volume 64 , Issue 4 , August 2000 , pp. 641 - 650
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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