Carbonatite Melts and Electrical Conductivity in the Asthenosphere
Fabrice Gaillard,1*
Mohammed Malki,2,3
Giada Iacono-Marziano,1,4
Michel Pichavant,1
Bruno Scaillet1
Electrically conductive regions in Earth's mantle have been
interpreted to reflect the presence of either silicate melt
or water dissolved in olivine. On the basis of laboratory measurements,
we show that molten carbonates have electrical conductivities
that are three orders of magnitude higher than those of molten
silicate and five orders of magnitude higher than those of hydrated
olivine. High conductivities in the asthenosphere probably indicate
the presence of small amounts of carbonate melt in peridotite
and can therefore be interpreted in terms of carbon concentration
in the upper mantle. We show that the conductivity of the oceanic
asthenosphere can be explained by 0.1 volume percent of carbonatite
melts on average, which agrees with the carbon dioxide content
of mid-ocean ridge basalts.
2 Conditions Extrêmes et Matériaux: Haute Température et Irradiation (CEMHTI), CNRS, UPR3079, 1D Avenue de la Recherche Scientifique, 45071 Orléans cedex 2, France.
3 Ecole Polytechnique de l'Université d'Orléans, 8 Rue Léonard de Vinci, 45072 Orléans cedex 2, France.
4 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italy.
* To whom correspondence should be addressed. E-mail: gaillard{at}cnrs-orleans.fr
