¹Simone Pascucci et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70170]
¹Institute of Methodologies for Environmental Analysis (IMAA)-Italian National Research Council (CNR), Tito Scalo, Italy
Published by arrangement with John Wiley & Sons

Asteroid compositional analysis relies on comparing reflectance spectra with laboratory data from well-characterized meteorites. To advance this comparison, we performed a comprehensive laboratory analysis on a slab of the Northwest Africa (NWA) 7317—CR6 carbonaceous chondrite. We employed high-resolution Visible-Infrared (VIS-IR) imaging spectroscopy (0.4–5.1 μm) using the SPIM hyperspectral facility, integrated with high-spatial-resolution elemental mapping via SEM-EDS and EMPA-WDS. This multi-technique approach enabled the retrieval of surface composition at high spectral and spatial resolutions. Our results, supported by ICA/PCA and K-means classification methodologies, highlight the challenges of integrating VIS-IR spectroscopy and SEM/EMPA at the micrometer scale. While both techniques consistently infer an overall poikiloblastic/metamorphic texture dominated by an olivine and pyroxene-rich matrix, their combined use requires a critical approach for robust analysis. The absence of the 3 μm absorption band indicates high temperatures during thermal metamorphism on the NWA 7317 parent body. Although FeNi metallic alloys and Fe-sulfide inclusions contribute to the VIS-IR spectroscopic signal, they are not clearly distinguishable from each other. Furthermore, minor phases like plagioclase and chromite detected via SEM/EMPA are not plainly visible in the SPIM results. We review the potential of integrating these techniques to assess the petrography, mineralogy, and terrestrial weathering of NWA 7317.

¹Christina Hamilton,²Shannon Dulin,³John Weber,²R. Douglas Elmore
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70139]
¹BP, Houston, TX, USA
²School of Geosciences, University of Oklahoma, Norman, Oklahoma, USA
³Department of Geology, Grand Valley State University, Allendale, MI, USA
Published by arrangement with John Wiley & Sons

A paleomagnetic and petrographic study of host carbonate rocks and impact breccias at the Kentland impact structure was conducted to better constrain the timing of the impact and to test for alteration by hydrothermal fluids. The Ordovician-Silurian target rocks sampled are fossiliferous wackestone/packstones with minor dolomite. Polymict impact breccias, also sampled, occur as dikes/sills and contain clasts of dolomite, host carbonate, sandstone, sphalerite, and rare coated grains which contain clays, dolomite, calcite, and hexagonal silica resembling tridymite. The host carbonates contain brecciated zones near the polymict breccias that display flow textures of aligned and elongated clasts and minerals. Authigenic minerals present include sylvite, apatite, gypsum, magnetite, and hematite. These observations suggest alteration by hydrothermal fluids, which probably had an estimated duration of ~7500 yrs after impact. Alternating field (AF) and thermal demagnetization of impact breccia and host carbonate specimens removed two post-tilting magnetic components: one with southerly declinations and moderate negative inclinations and the other with northerly declinations and positive inclinations. Demagnetization results suggest the magnetizations primarily reside in magnetite as well as hematite and possibly pyrrhotite. Petrographic and rock magnetic results are consistent with this interpretation. These magnetizations are interpreted as chemical remanent magnetizations acquired through a reversal, which formed from alteration by hydrothermal fluids generated after the impact. The paleomagnetic poles (mean pole, 75.7° N, 98.4° W) fall near the Early Jurassic part of the apparent polar wander path, which suggests the alteration in the breccias, and likely the impact, occurred in the Early Jurassic (175–185 Ma).