Timing and Source of Alkali Enrichment at Mt. Etna, Sicily: Constraints from Clinopyroxene Geobarometry and In Situ SR Isotope Data

Since 1971, Mt. Etna, Europe’s largest and most active volcano, has exhibited increased eruption frequency and explosivity. Associated with this increased activity, researchers have documented higher abundances of alkali elements (K, Rb, Cs) as well as elevated ⁸⁷Sr/⁸⁶Sr in Etnean lavas. The source of this alkali-enrichment has been hotly debated, with end-member hypotheses involving mantle vs. crustal contributions. To further characterize the evolution of the subvolcanic magma storage and transport system, as well as the timing and source of alkali-enrichment, clinopyroxene from ten samples erupted between 1329 and 2004 was targeted for <em>in situ</em> textural, major element and Sr isotope analysis. Clinopyroxene disequilibrium textures paired with increased Mg# values imply recharge/mixing at work within a dynamic magmatic system. Calculated pressures also reveal a dominant crystallization zone between ~8.7 and 16.5 km within the volcano’s carbonate substratum. A select population of clinopyroxene exhibits increasing weight percent CaO and Mg# with decreasing pressure, providing new evidence for late-stage carbonate assimilation enhanced by magmatic recharge. Alkali-enrichment is thus likely a consequence of both magma recharge and crustal assimilation.

Name thesis:degree_name

Master of Science (MS)

Discipline thesis:degree_discipline

Geological Sciences

Year dc:date.available

2015

Author dc:creator

• Nelson, Kaitlyn

Contributors dc:contributor

• Wendy A. Bohrson
• Chris Mattinson
• Jeffrey Lee

• Mt. Etna
• igneous petrology
• basalt
• computational modeling
• crustal assimilation
• carbonate
• Geochemistry
• Geology
• Volcanology

Language dc:language

English

Repository record dc:identifier

https://digitalcommons.cwu.edu/etd/276

OAI identifier oai:identifier

oai:digitalcommons.cwu.edu:etd-1286