Shock Metamorphic Effects in Lunar and Terrestrial Plagioclase Feldspar Investigated by Optical Petrography and Micro-X-Ray Diffraction
Master of Science
Dr. Gordon Osinski
Dr. Roberta Flemming
Shock metamorphism, caused by hypervelocity impact, is a poorly understood process in feldspar. This thesis addresses: a) developing a quantitative scale of shock deformation in plagioclase feldspar; b) expanding the utility of plagioclase feldspar for determining shock level; and c) micro-X-ray diffraction as a technique with which to study shock in feldspar.
Andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada, and anorthite from Earth’s moon, returned during the Apollo program, show shock effects such as diaplectic glass. Planar deformation features are absent in plagioclase, but abundant in terrestrial quartz. A pseudomorphous zeolite phase (levyne-Ca) was identified as a replacement mineral of diaplectic feldspar glass in some terrestrial samples. Micro-X-ray diffraction patterns revealed increased peak broadening in the chi direction (χ) (due to strain-related mosaicity) with increased optical signs of deformation. Measuring the full-width-at-half-maximum (FWHMχ) of these peaks provides a quantitative way to measure strain in shocked samples.
Pickersgill, Annemarie E., "Shock Metamorphic Effects in Lunar and Terrestrial Plagioclase Feldspar Investigated by Optical Petrography and Micro-X-Ray Diffraction" (2014). Electronic Thesis and Dissertation Repository. 2094.