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Titel Gas-driven filter pressing: insights into melt segregation from crystal mushes
VerfasserIn Mattia Pistone, Fabio Arzilli, Benoit Cordonnier, Katherine Dobson, Eric Reusser, Peter Ulmer, Federica Marone, Alan Whittington, Lucia Mancini, Julie Fife, Jonathan Blundy
Konferenz EGU General Assembly 2015
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 17 (2015)
Datensatznummer 250106632
Publikation (Nr.) Volltext-Dokument vorhandenEGU/EGU2015-6310.pdf
 
Zusammenfassung
Gas-driven filter pressing relieves the gas pressure developed through second boiling by expelling melt from a crystal mush. It is thought to play a major role in magma fractionation at shallow depths (< 10 km). We present new 4D (3D and time) experimental data that constrain conditions under which gas-driven filter pressing can occur. We performed in-situ high-temperature high-speed synchrotron X-ray tomography (500-800 °C, 3 μm/pixel, 8 seconds per full 3D dataset) to collect real time information on the behaviour of hydrous haplogranitic (2.1 wt.% H2O) and dacitic (4.2 wt.% H2O) crystal mushes with a wide range of crystal contents (34-80 vol.%). The data constrain how the crystal content affects the efficiency of gas-driven filter pressing of silicic melt out of the crystal mush framework, and show that gas-driven filter pressing operates below the maximum packing fraction of the suspended phases (bubbles + crystals) of ~74 vol.%. Above this value, the crystal mush is fated to fracture. These results provide essential constrain on the physical conditions under which gas-driven filter pressing can efficiently operate and force silicic melt out of the crystal framework. This also implies that, for effective gas-driven filter pressing, the crystal mush must inflate slowly relative to build-up of pressure and expulsion of melt. These observations suggest a possible explanation for the production of eruptible crystal-poor rhyolites in the Earth’s crust.