Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type

Thesis

Type of Thesis

General Honors

Department

Geological Sciences

First Advisor

Rebecca Flowers

Second Advisor

Charles Stern

Third Advisor

Thomas Roberts

Abstract

Radiation damage has a strong influence on He diffusion kinetics and the temperature sensitivity of (U-Th)/He thermochronometers. Understanding these effects is critical for the accurate interpretation of (U-Th)/He datasets and can lead to more detailed thermal history reconstructions. This information is particularly important for settings with protracted thermal histories, such as the Kaapvaal Craton, where U and Th-rich minerals have accumulated significant radiation damage. Models for how radiation damage influences He diffusion kinetics have been published for apatite (Flowers et al., 2009) and zircon (Guenthner et al., 2013). However, the kinetic model for zircon is less calibrated at the higher damage end of the spectrum. Negative date-effective uranium (eU) correlations in zircon from the Kaapvaal Craton suggest the variable influence of radiation damage on the data. I used Raman spectroscopy to quantitatively and qualitatively characterize the variable magnitudes of radiation damage in this zircon suite. Our measurements of Raman Spectra full width at half maximum (FWHM) show a range of closure temperatures spanning ~50 ºC. This variation can explain the presence of negative date-eU correlations. Furthermore, our research showed that Raman spectroscopy could characterize zonation in radiation damage.

Share

COinS