9527273 Smith Alternation between explosive and non-explosive eruptive modes at Mt. Pelee provides an excellent natural example to study the relationship between volatiles and eruptive mechanism. Accordingly, this project will test quantitatively the hypothesis of Smith and Roobol (1990a), which state that the main control on eruptive style of Mt. Pelee is not magma composition but gas content: volatile-rich magma generate explosive Plinian activity and volatile-poor magma generates Pelean activity. This will be accomplished by measuring the contents of pre-eruptive volatiles (H2O, CO2, Cl, F, and S) using microinfrared spectroscopy and electron and secondary ion mass spectrometry microscopy (ion probe) on juvenile glasses and melt inclusions in phenocrysts from both Plinian and Pelean deposits of Mt. Pelee. Trace elements will be measured using an ion microprobe. The evolution and degassing history of the volatiles will be interpreted within a framework of fractional crystallization models based on major and trace elements and open versus closed system degassing models.
