Document Type

Thesis

Date of Degree Completion

Spring 2009

Degree Name

Bachelor of Science

Department

Geological Sciences

Committee Chair

Dr. Wendy A. Bohrson, Geological Sciences

Second Committee Member

Dr. Jeff Lee, Department of Geological Sciences

Third Committee Member

Dr. Audrey D. Huerta, Director Science Honors Research Program

Abstract

Mt. Rainier is an active composite volcano located in the Cascade volcanic arc, ~90km southeast of Seattle, Washington. Based on a compilation of data representing basaltic andesites through dacites, thermodynamic simulations have been run to constrain the mechanisms of formation of the typical liquid line of descent. Using a variety of parental magmas and iterating through parameters such as water content, pressure, and oxygen fugacity, the best fit models suggest magmas are stored at shallow levels and have initial water contents of~ 1-2.0 wt. % and oxygen fugacity of ~QFM+ 1 to +2. One lava flow, classified as a spessartite, is anomalous when compared to the typical Rainier lavas. Thermodynamic models are not able to reproduce spessartite signatures and electron microprobe data on phenocryst populations indicate assimilation was important. Further work is required to determine the origin of the spessartite.

Comments

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