Abstract

Quenched glass rinds that form during lava-ice interactions on pillow lavas have proven to be helpful in constructing models for paleo-ice thickness of previously glaciated regions (Jakobbson and Gudmundsson, 2008). Glass samples were acquired from a variety of pillow exposures at Pillow Ridge tindar in the Mount Edziza Volcanic Complex of (MEVC). Here, we combine Fourier Transform Infrared Spectrometry (FTIR) analysis of volatiles in 95 doubly polished glass chips with whole rock major element (XRF) analysis, an igneous thermodynamic modeling program for calculating liquid phase equilibria (rhyolite-MELTS), and the VolatileCalc solubility model to calculate emplacement pressures as a proxy for ice thickness at Pillow Ridge (178-925m). Ice thickness calculations were highly variable for the Ridge, although for pillow units, minimum pressures converge at ~20 bars, which is similar to data collected at Iceland (Reinthal et al., 2016). We have determined that the simplifying assumption that that lower overburden pressures create fragmented basalt and that higher pressures will create effusive eruptions should be revised to incorporate complex relationships among eruptive dynamics, magmatic conditions, and ice thickness. We determined that the northern canyons of Pillow Ridge—Pillow Canyon and Slot Canyon—fit into the general Pillow Ridge lithostratigraphy via sub-ice drainage events that occurred during the evolution of the Ridge. With this, we have established a new model for Pillow Ridge combining two previously existing models and further constraining the ice sheet thicknesses for the different pillow packages.

Advisor

Pollock, Meagen

Department

Geology

Disciplines

Geochemistry | Geology | Volcanology

Publication Date

2016

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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© Copyright 2016 Mary C. Reinthal