Analyzing Compositional Trends in Plagioclase Crystals Erupted from Mt. Etna

Since 1971, Mt. Etna has experienced an increase in eruption frequency and explosivity, thereby posing a significant hazard to the nearby city of Catania. Coupled to these behavioral changes are changes in magma chemistry in post-1971 lavas. The two major contending hypotheses proposed to address the source and timing of these changes are: (1) new magma entering the Etna magma storage zone via magma recharge from below the crust, and (2) late stage assimilation of shallow crustal rock into the magma storage zone. The mineral plagioclase shows evidence of assimilation, and I will therefore focus on collecting core to rim element data from plagioclase crystals found in rocks that were erupted before and after 1971 using a laser mass spectrometer. Behavior of particular elements such as rubidium, magnesium and iron will allow me to distinguish which hypothesis is responsible for the chemical changes and increased activity at Mt. Etna. Analysis of these crystals has yet to be determined. If the cause for Mt. Etna’s change in magma chemistry is the result of crustal assimilation, then the expectation is that these plagioclase crystals will show in a core to rim transect a significant increase in rubidium while showing little to no change in iron or magnesium content. If the magma recharge hypothesis is the cause, then the expectation is that these plagioclase crystals will show little to no increase in rubidium while showing a significant increase in iron and magnesium