3D petrography of Enstatite achondrites via micro computed tomography scanning (µCT)

English Abstract:

Enstatite achondrites are thought to have formed under highly reducing conditions, and are composed of enstatite, plagioclase, native iron (kamacite), troilite and various trace phases. Understanding the petrogenesis of these rare meteorites may provide information about early planetary formation processes, particularly in the region of the solar nebula near the proto-Sun. µCT allows for non-destructive analysis of meteorite samples and provides three dimensional imaging of internal density structures. Enstatite achondrite samples including Zaklodzie, NWA 4301, Itqy, Hvittis, NWA 8751, and Abee were imaged with the Locus RS-9 scanner, at an X-ray tube voltage of 80 kVp and a tube current of 0.45 mA. 900 views were collected at angular increments of 0.4^o around the samples. The aforementioned meteorites were selected in order to observe and compare 3D structures of enstatite achondrites having different formation mechanisms. µCT images of the enstatite achondrites studied reveal density contrasts between high and low attenuation phases, and also show the overall distribution of metal and silicate throughout the samples. µCT may also be used to identify the weathering extent of the samples which is useful when trying to analyse the least altered material or when trying to identify where to cut the sample for thin section preparation. Threshold value limits were selected for high intensity and low intensity phases and were compared to reported values in literature. Although µCT cannot yet discern between each individual phase present in the samples, it is possible to determine a combined modal percent volume for metal + sulphides and silicates + plagioclase. Isosurface rendering of high-intensity phases was used to visualize the distribution, size, shape and interconnectedness of metal grains in the samples which may help further understand their petrogenetetic sequence.