Title

Timing and Source of Alkali-Enrichment at Mt. Etna, Sicily using Clinopyroxene Geobarometry and in situ Sr Isotope Data

Document Type

Oral Presentation

Location

SURC Ballroom C/D

Start Date

15-5-2014

End Date

15-5-2014

Keywords

Mt. Etna, Volcanology, Eruption

Abstract

Since 1971, Mt. Etna, Europe’s largest and most active volcano, has exhibited increased eruption frequency and explosivity. In association with this increased activity, researchers have documented higher abundances of alkali elements such as potassium and rubidium as well as elevated Sr isotopes (87Sr/86Sr) in Etnean lavas. The source of this alkali-enrichment has been hotly debated, with end-member hypotheses involving mantle vs. crust. While some researchers favor changes in the character of the mantle source region due to subduction, in situ plagioclase compositional data suggest the mineral crystallizes in the shallow crust (upper 12 km) and Sr isotopic data provide strong evidence for late-stage crustal assimilation as demonstrated by increasing 87Sr/86Sr in magma after plagioclase had begun to grow. To further evaluate the mantle vs. crustal debate, clinopyroxene, which forms at deep and shallow levels within the magma chamber, was targeted for in situ analysis. Compositional and isotopic data were collected for ten samples erupted between 1329 and 2004. The largest, most complexly-zoned clinopyroxene were analyzed for elemental concentration by electron microprobe, and these data were used to calculate pressures of formation for each crystal. Pressures range from deep (~27 km) to upper crust (~6.0-6.6 km). In situ 87Sr/86Sr of clinopyroxene data will be combined with this information to provide a window into the middle to lower crustal dynamics of the Etnean magma storage system, as well as a characterization of mantle and crustal contributions of the recent alkali-enrichment event.

Poster Number

42

Faculty Mentor(s)

Bohrson, Wendy

Additional Mentoring Department

Geological Sciences

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Timing and Source of Alkali-Enrichment at Mt. Etna, Sicily using Clinopyroxene Geobarometry and in situ Sr Isotope Data

SURC Ballroom C/D

Since 1971, Mt. Etna, Europe’s largest and most active volcano, has exhibited increased eruption frequency and explosivity. In association with this increased activity, researchers have documented higher abundances of alkali elements such as potassium and rubidium as well as elevated Sr isotopes (87Sr/86Sr) in Etnean lavas. The source of this alkali-enrichment has been hotly debated, with end-member hypotheses involving mantle vs. crust. While some researchers favor changes in the character of the mantle source region due to subduction, in situ plagioclase compositional data suggest the mineral crystallizes in the shallow crust (upper 12 km) and Sr isotopic data provide strong evidence for late-stage crustal assimilation as demonstrated by increasing 87Sr/86Sr in magma after plagioclase had begun to grow. To further evaluate the mantle vs. crustal debate, clinopyroxene, which forms at deep and shallow levels within the magma chamber, was targeted for in situ analysis. Compositional and isotopic data were collected for ten samples erupted between 1329 and 2004. The largest, most complexly-zoned clinopyroxene were analyzed for elemental concentration by electron microprobe, and these data were used to calculate pressures of formation for each crystal. Pressures range from deep (~27 km) to upper crust (~6.0-6.6 km). In situ 87Sr/86Sr of clinopyroxene data will be combined with this information to provide a window into the middle to lower crustal dynamics of the Etnean magma storage system, as well as a characterization of mantle and crustal contributions of the recent alkali-enrichment event.