Nano-FTIR Investigation of the CM Chondrite Allan Hills 83100

1J. M. Young,1T. D. Glotch,2M. Yesiltas,3V. E. Hamilton,4L. B. Breitenfeld,5H. A. Bechtel,5S. N. Gilbert Corder,5Z. Yao
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007166]
1Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
2Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, Turkey
3Southwest Research Institute, Boulder, CO, USA
4Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
5Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

Mid-infrared (MIR) spectroscopy has been used with great success to quantitatively determine the mineralogy of geologic samples. It has been employed in a variety of contexts from determining bulk composition of powdered samples to spectroscopic imaging of rock thin sections via micro-FTIR. Recent advances allow for IR measurements at the nanoscale. Near field nanoscale infrared imaging and spectroscopy with a broadband source (nano-FTIR) enable understanding of the spatial relationships between compositionally distinct materials within a sample. This will be of particular use when analyzing returned samples from Bennu and Ryugu, which are thought to be compositionally like CI or CM2 carbonaceous chondrites. Returned samples will likely contain olivine/pyroxene chondrules that have been transformed into hydrous phyllosilicates, sulfides, carbonates, and other alteration phases. The use of near-field infrared techniques to probe the boundaries between once pristine chondrules and alteration phases at the nanoscale is a novel approach to furthering our understanding of the compositional evolution of carbonaceous asteroids and the processes that drive their evolution. Here we report the results of nano-FTIR spectroscopy and imaging measurements performed on the carbonaceous chondrite Allan Hills (ALH) 83100 (CM1/2). We show with nanoscale resolution that spatially resolved Fe-Mg variations exist within the phylosilicates around a chondrule rim. We also present effects of crystal orientation on the nano-FTIR spectra to account for the spectral differences between the meteorite and mineral spectra.

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