Volcanological features of a low-viscosity melt: the carbonatitic Gross Brukkaros Volcanic Field, Namibia |
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Authors: | Stephan Kurszlaukis Volker Lorenz |
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Institution: | (1) Institut für Geologie, Pleicherwall 1, D-97070 Würzburg, Germany Fax: ++49–931–57705, DE |
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Abstract: | In the Upper Cretaceous Gross Brukkaros Volcanic Field, southern Namibia, a radial dyke system surrounds a dome structure
and its 74 closely related carbonatite diatremes. This paper focuses on volcanological features which seem to be typical for
a low-viscosity melt in various settings such as dykes, sills and diatremes. The total or near absence of vesicles in carbonatite
ash grains and lapilli inside the diatremes is evidence against explosive exsolution of volatile phases and in favour of a
phreatomagmatic fragmentation mechanism and thus for a phreatomagmatic eruption mechanism of the carbonatite diatremes.
Received: 15 August 1996 / Accepted: 13 January 1997 |
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Keywords: | Carbonatite Dykes Diatremes Gross Brukkaros Phreatomagmatism Namibia |
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