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Extensive dolomitic volcanism through the Limagne Basin, central France: a new form of carbonatite activity

Published online by Cambridge University Press:  05 July 2018

K. Bailey*
Affiliation:
Department of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, UK
S. Kearns
Affiliation:
Department of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, UK
J. Mergoil
Affiliation:
Université Blaise Pascal - Departement des Sciences de la Terre, 5, rue Kessler, F-63000 Clermont-Ferrand cedex, France
J. Mergoil Daniel
Affiliation:
Université Blaise Pascal - Departement des Sciences de la Terre, 5, rue Kessler, F-63000 Clermont-Ferrand cedex, France
B. Paterson
Affiliation:
Department of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, UK
*

Abstract

Recognition of widespread carbonate volcanism in central Spain has led to another case in France, of similar age (23–0 Ma) but with entirely new features. More than 100 new carbonate volcanoes are indicated already, adding a wholly unexpected dimension to this form of activity. Eruptions form layers, mostly of glassy nephelinite fragments in a dolomitic matrix, but some layers are largely dolomite. Major new findings are phenocrysts of dolomite, magnesite and calcite in silicate glass, and spectacular dolomite-nephelinite melt immiscibility, neither recorded previously. Most volcanic carbonatites are Ca rich, and dolomite is rare. The Limagne dolomites share links with those in Spain and Zambia, with chromite a hallmark in all three. Limagne is exceptional in being the first case where dolomite has erupted with co-genetic silicate melt. Mantle debris and magnesite indicate a source within ∼ 100–150 km. Chromite in the dolomite globules, and in the enclosing silicate glass, is similar to that in high-temperature kimberlites, indicating immiscibility in the deep mantle. Recognition of two large, previously undetected provinces of carbonate volcanism in Europe, where there has been active research for >200 y, must lead to the inference that similar cases may await discovery on other continents.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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