Global warming of the mantle at the origin of
fl ood basalts over supercontinents

N. Coltice*, B. Phillips**, H. Bertrand, Y. Ricard and P. Rey***

* Laboratoire de Sciences de la Terre, UMR-CNRS 5570, Université Lyon 1, Bat Geode,
2 rue Raphael Dubois, 69622 Villeurbanne Cedex, France.
Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
* EarthByte Group, School of Geosciences, Edgeworth Building F05,
The University of Sydney, Sydney NSW 2006, Australia

Geology (2007) 35-5, 391-394

ABSTRACT

Continents episodically cluster together into a supercontinent, eventually breaking up with intense magmatic activity supposedly caused by mantle plumes (Morgan, 1983; Richards et al., 1989; Condie, 2004). The breakup of Pangea, the last supercontinent, was accompanied by the emplacement of the largest known continental fl ood basalt, the Central Atlantic Magmatic Province, which caused massive extinctions at the Triassic-Jurassic boundary (Marzoli et al., 1999). However, there is little support for a plume origin for this catastrophic event (McHone, 2000). On the basis of convection modeling in an internally heated mantle, this paper shows that continental aggregation promotes large-scale melting without requiring the involvement of plumes. When only internal heat sources in the mantle are considered, the formation of a supercontinent causes the enlargement of fl ow wavelength and a subcontinental increase in temperature as large as 100 °C. This temperature increase may lead to large-scale melting without the involvement of plumes. Our results suggest the existence of two distinct types of continental fl ood basalts, caused by plume or by mantle global warming.

ACKNOWLEDGMENTS

We thank M. Gurnis and two anonymous reviewers for helpful comments. We thank P. Planton and A. Dechamps for being there when we started.

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