A SPECTROSCOPIC INVESTIGATION OF THE MINERALOGY OF SHOCK-GENERATED MELTS WITHIN THE NORTHWEST AFRICA 6234 MARTIAN METEORITE

The study of meteorites is critical to our understanding of impact processes. Impact induced shock metamorphism ( i.e. amorphization, shock-melting, and crystallization of high-pressure high-temperature (HP-HT) mineral phases) occurs as observable features within meteorite samples that can be used to estimate the impact conditions the sample experienced. In particular, HP-HT minerals found within or adjacent to shock-melts are useful as they can provide upper and lower bounds to impact condition estimates if their stability ranges are known. The goal of our study is to identify HP-HT minerals associated with shock-generated melt veins within samples, in particular maskelynite and related phases. Here, we examine an olivine-phyric shergottite Martian meteorite NWA 6234. The dominant mineralogy includes mm-size olivine macrocrysts within a fine-grained groundmass largely composed of pyroxene, olivine, spinel, and plagioclase (now maskelynite). The sample is a thick section, ~2cm wide and 3 mm thick, with a large melt vein, <200 µm thick, that cross cuts the sample. Here we specifically targeted areas within and around the melt vein, as these areas may exhibit a higher frequency of HP-HT phases that formed as a result of an impact event. Areas of interest were first identified using reflected light microscopy. These areas were then investigated using SEM and micro-raman spectral imaging techniques. Our initial Raman mapping results indicate the presence of the high-pressure phases maskelynite, ringwoodite, and possibly tuite. Further investigation of the sample is ongoing, and will include micro-FTIR spectral maps and 3-D Raman maps of areas within our sample.