Date of Award
Master of Science (MS)
Calcic pyroxenes are a group of silicate minerals that are found in meteorite and asteroid spectra. I investigated the relationship of high-calcium clinopyroxenes in comparison with orthopyroxenes, pigeonites, mixtures, and the meteorite group of angrites to try to find any trends for spectral calibrations. I used spectra from HOSERLab, RELAB, and the USGS Spectral Library. The main band minima of pyroxenes in spectra are around 0.9 or 1 µm for band I and 1.15 or 2 µm for band II, with the former minima for type A clinopyroxenes and the latter for type B. Using sample minima found from both lowest reflectances and polynomial fittings, I graphed the different pyroxene features to view possible trends from band positions and calcium, iron, and magnesium abundances. The type B clinopyroxenes continued on previous trends found in the literature, having a stronger band position relationship for the iron and calcium contents than the type A clinopyroxene samples. However, their band position relationships with iron and calcium were much less linear than the orthopyroxenes, which has also been seen previously in the literature. The two main band minima found from the different methods were similar in band position for band I, while due to noise and slope, the band II features were more diverse. I also examined how calcic clinopyroxenes interacted in comparison to other minerals in mixtures. There did not appear to be a trend for the type A clinopyroxenes, although it was also complicated by the larger error in band positions from reddened slopes and faintness. When in mixtures with orthopyroxene and/or olivine there needed to be a large amount, usually around ≥ 70 % calcic pyroxene, before the minima could be found. Angrite spectra were also looked at because they typically have a large amount of calcic clinopyroxene, including type A, although usually with larger amounts of titanium and aluminum. There were limited samples so I was unable to find any trends from them, but I investigated a set of mixtures from Cloutis et al. (2006a) and a set made for this study from HOSERLab that were made to resemble possible angrite and angrite parent-body spectra. From these, more data were available to show how a combined 1 µm feature from type A high-calcium pyroxene and olivine changes with differing amounts of both.
Dievendorf, Margaret, "Calibration Of Calcic Pyroxenes For Interpreting Meteorite And Asteroid Spectra" (2018). Theses and Dissertations. 2401.