Raman Study of Shocked Plagioclase from the Mistastin Lake Impact Structure and the Apollo Samples
Abstract
Anorthosite is one of the most abundant rock types found on lunar surface and expected to be subjected to heavy bombardment during the early stage of evolution. As detailed spectroscopic study on shocked anorthosites has been limited, we systematically examined the shock features of anorthosites from both Mistastin Lake impact structure, Canada and lunar samples from the Apollo missions using Raman spectroscopy. In this study, polished thin sections from Mistastin Lake and Apollo samples were observed under microscope. The feldspar compositions were determined by electron-microprobe analyses (EMPA), and their crystal structures were obtained by powder X-ray diffraction (XRD). Raman spectroscopy was performed using a 514.5 nm laser with a laser spot size about 2μm. EPMA results showed that the anorthosite samples have an average plagioclase composition of labradorite ( An55) from Mistastin and anorthite ( An95) for the Apollo samples. Five different shock levels were observed in plagioclase from both sites. The Raman spectra, including full widths at half maximums (FWHM) and peak intensity, show similar trends consistent with progressive shock metamorphism. Comparing the Raman spectra collected from naturally shocked plagioclase samples with high pressure experimental data, dynamic shocked basalt and thermal melt glass, the results suggest the ones of diaplectic glass show distinct features from the ones of shock melt. Our study suggests that Raman spectroscopy is an efficient and promising tool to better understand shock effects in plagioclase and could play an important role in future exploration missions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P42C..29X
- Keywords:
-
- 3625 Petrography;
- microstructures;
- and textures;
- MINERALOGY AND PETROLOGYDE: 3656 Ultra-high temperature metamorphism;
- MINERALOGY AND PETROLOGYDE: 6240 Meteorites and tektites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5420 Impact phenomena;
- cratering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS