Dissertation/Thesis Abstract

Argon Diffusion in Rhyolite Melt at 100 MPa
by Weldon, Nicholas Cullum, M.S., University of California, Davis, 2016, 86; 10165710
Abstract (Summary)

In this study, we conduct high-pressure (HP) high-temperature (HT) diffusion experiments in anhydrous rhyolite near 1000 °C and 1100 °C at 100 MPa using the cold seal pressure apparatus to diffuse argon into natural obsidian charges. We use electron microprobe measurements of the argon concentration gradients to calculate the argon diffusivity (DAr) as a function of temperature and pressure. The range and mean of DAr calculated from these measurements are in good agreement with previous studies (Carroll 1991, Behrens and Zhang 2001). Even so, we observe significant variability in our DAr results, beyond what is likely due to analytical or experimental uncertainty; nearly as much variability as Carroll (1991) and Behrens and Zhang (2001) reported. In particular, we notice a small systematic geometric bias in the distribution of argon in our samples, which appears to correlate with sample deformation. We attribute this effect to distortion of concentration gradients by viscous advection.

Indexing (document details)
Advisor: Lesher, Charles E.
Commitee: Lesher, Charles E., Mukhopadhyay, Sujoy, Watkins, James M.
School: University of California, Davis
Department: Geology
School Location: United States -- California
Source: MAI 56/01M(E), Masters Abstracts International
Subjects: Geology, Geochemistry
Keywords: 40ar/39ar dating, Diffusion, Experimental petrology, High pressure, High temperature, Rhyolite
Publication Number: 10165710
ISBN: 9781369200867
Copyright © 2019 ProQuest LLC. All rights reserved. Terms and Conditions Privacy Policy Cookie Policy