HR: 1340h
AN: V13B-0526    [Abstracts]
TI: Constraining Pre-Eruptive Storage Conditions at Nea Kameni, Santorini
AU: * Hunt, C A
EM: carol.hunt@uea.ac.uk
AF: School of Environmental Science, University of East Anglia, Earlham Road, Norwich, NR4 7TJ United Kingdom
AU: Barclay, J
EM: j.barclay@uea.ac.uk
AF: School of Environmental Science, University of East Anglia, Earlham Road, Norwich, NR4 7TJ United Kingdom
AU: Pyle, D M
EM: dmp11@esc.cam.ac.uk
AF: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ United Kingdom
AB: Santorini is one of the most active volcanic centres on the South Aegean Volcanic Arc. Historic volcanism culminated in the catastrophic eruption in 1600BC which destroyed the Minoan civilisation and generated a water filled caldera 8 km long and 4 km wide. Recent activity has been confined to formation of two intra-caldera shield volcanoes, the Kameni islands, the last eruption occurring in 1950. The Kameni lavas are sparsely porphyritic dacites containing phenocrysts of labradorite, augite, hypersthene and magnetite. Xenocrysts of olivine, anorthite and Mg-rich augite are derived from the disaggregation of mafic xenoliths. The most striking feature of these lavas is their relatively homogeneous nature despite 2000 years of activity. The low variability in silica content (64-68 wt. %) has prompted suggestions that the chamber may be chemically or thermally buffered. Even with numerous petrological studies, little is known about the dynamics of the system. In this instance experimental phase equilibria are unequivocally one of the best ways of establishing the `real' phenocryst assemblage. This research uses phase equilibria experiments to constrain pre-eruptive storage conditions at Nea Kameni. Using a natural sample from the 1866-1870 Georgios lavas as a starting composition, a series of water-saturated experiments have been undertaken in a rapid quench Cold Seal Pressure Vessel over a temperature and pressure range of 800-900°C and 80-150 MPa. Comparison of the experimental phase equilibria with the natural assemblage suggests magma storage at water saturated conditions at >900 °mathrm{C} and >100 MPa. These results suggest the magma chamber is at a depth of ~2.8-3.5 km, which is comparable to the calculated depth estimates of earlier studies (2-4 km). Further experiments at higher temperatures will constrain the system more closely and these results will also be presented.
DE: 8412 Reactions and phase equilibria (1012, 3612)
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005