Séminaire ISTeP - John Mc Lennan

(Cambridge)

Mixing and mushes in magma chambers under Iceland

The 2010 eruption of Eyjafjallajokull focussed a great deal of attention onto methods for understanding pre-eruptive processes in Icelandic magma chambers. Here, we summarise some recent findings relating to the characteristics of Icelandic magmatic systems. We use melt inclusion trace element compositions to demonstrate that diverse mantle melts are mixed in chambers in the lower crust and uppermost mantle. This mixing is concurrent with crystallisation and is likely to be driven by convection. Petrological constraints on the relative rates of mixing and cooling can be combined with the results of simple physical models of convection in sills to provide information about the likely size of the magma chambers that dominate the evolution of Icelandic melts. We also describe novel petrogical methods for characterising the properties of crystal mushes in basaltic systems, providing a possibility for bridging the divide between studies of plutonic and volcanic rocks.

02/07/2014 à 12h30, Salle Fourcade (Tour 55-56, 4ème étage)