HR: 11:25h
AN: V42B-05    [Abstracts]
TI: Determination of the Degassing Depth at Popocatepetl volcano (Mexico) Using Data From Olivine-Hosted Melt Inclusions
AU: * Roberge, J
EM: roberge@geofisica.unam.mx
AF: Laboratorio Universitario de Petrologia, Av Universidad 3000 Coyoacan, Mexico, DF 04510, Mexico
AU: Delgado Granados, H
EM: hugo@geofisica.unam.mx
AF: Instituto de Geofisica, Av Universidad 3000 Coyoacan, Mexico, DF 04510, Mexico
AU: Wallace, P J
EM: pwallace@uoregon.edu
AF: Dept. Geological Sciences, U of O, University of Oregon, Eugene, OR 97403, United States
AB: Volatiles are fundamental for magma ascent, and therefore volcanic eruptions. Either in dissolved or exsolved form, these gases strongly control magma behavior during its ascent. However, because they are released during eruption, the gases leave little trace of their earlier presence. Magmatic inclusions such as silicate-melt inclusions in phenocrysts represent a vital source of information about the compositions of magmatic fluids during eruptive ascent. Previous work has been done on plagioclase- and pyroxene-hosted melt inclusions to characterize melt evolution at Popocatépetl volcano (Atlas et al., 2006). Our work focuses on olivine-hosted melt inclusions from ashes emitted during 2 major vulcanian eruptions of Popocatépetl (May 11th and June 30th 1997 eruptions). The olivine-hosted melt inclusions were analyzed for major and volatile elements using an electron probe and Fourier transform infrared (FTIR) spectroscopy (for H2O and CO2 contents). As expected, the volatile contents (H2O and CO2) of olivine-hosted melt inclusions represent a much deeper magma (up to 40 km depth) and therefore allow a better constrain on the degassing processes. Previous work at Popocatépetl volcano suggests the presence of a magma chamber that puts materials out in a stepwise fashion (Schaaf et al., 2005). In contrast, other study suggests a dyke system along which, magma is moving in a continuous mode (Atlas et al., 2006). Our new data indicate that Popocatépetl volcano is fed by a dyke system in which magma move upwards in a stepwise manner until about 10 km depth. At levels shallower than 10 km, stronger degassing starts to occur and from this point magma would be ascending in a continuous way. Popocatépetl volcano is located close to densely populated areas (Mexico City and Puebla metropolitan area), and therefore, evaluation of hazards associated with explosive eruptions is crucial. The new data allow a better understanding of the degassing processes occurring at depth and the recognition of changes in eruption behavior of Popocatepetl volcano.
DE: 1036 Magma chamber processes (3618)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly