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Toward quantification of strain‐related mosaicity in shocked lunar and terrestrial plagioclase by in situ micro‐X‐ray diffraction
Author(s) -
Pickersgill Annemarie E.,
Flemming Roberta L.,
Osinski Gordon R.
Publication year - 2015
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12514
Subject(s) - plagioclase , feldspar , mosaicity , geology , shock metamorphism , petrography , geochemistry , anorthite , augite , meteorite , mineralogy , diffraction , x ray crystallography , physics , astrobiology , optics , quartz , paleontology
Studies of shock metamorphism of feldspar typically rely on qualitative petrographic observations, which, while providing invaluable information, can be difficult to interpret. Shocked feldspars, therefore, are now being studied in greater detail by various groups using a variety of modern techniques. We apply in situ micro‐X‐ray diffraction (μ XRD ) to shocked lunar and terrestrial plagioclase feldspar to contribute to the development of a quantitative scale of shock deformation for the feldspar group. Andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada, and anorthite from Earth's Moon, returned during the Apollo program, were examined using optical petrography and assigned to subgroups of the optical shock level classification system of Stöffler (1971). Two‐dimensional μ XRD patterns from the same samples revealed increased peak broadening in the chi dimension (χ), due to strain‐related mosaicity, with increased optical signs of deformation. Measurement of the full width at half maximum along χ ( FWHM χ) of these peaks provides a quantitative way to measure strain‐related mosaicity in plagioclase feldspar as a proxy for shock level.