^1,2S. K. Bell,²K. H. Joy,^2,3M. Nottingham,²R. Tartèse,²R. H. Jones,⁴J. J. Kent,^5,6C. K. Shearer, the ANGSA science team
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008359]
¹Stratum Reservoir AS, Sandnes, Norway
²Department of Earth and Environmental Sciences, University of Manchester, Manchester, UK
³School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK
⁴GeoControl Systems Inc., Jacobs JETS Contract, NASA/JSC, Houston, TX, USA
⁵Department of Earth and Planetary Science, Institute of Meteoritics, University of New Mexico, Albuquerque, NM, USA
⁶Lunar and Planetary Institute, Houston, TX, USA
Published by arrangement with John Wiley & Sons

The Apollo 17 73001/73002 double drive tube, collected at the base of the South Massif in the Taurus-Littrow Valley, was opened in 2019 as part of the Apollo Next Generation Sample Analysis program (ANGSA). A series of continuous thin sections were prepared capturing the full length of the upper portion of the double drive tube (73002). The aim of this study was to use Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN), to search for clasts of non-lunar meteoritic origin and to analyze the mineralogy and textures within the core. By highlighting mineral groups associated with meteoritic origins, we identified 232 clasts of interest. The elemental composition of 33 clasts was analyzed using electron microprobe analysis that revealed that all clasts were of lunar origin, suggesting that any meteoritic component in the regolith material we studied is not present in the form of lithic clasts. In the process of searching for meteorite fragments, we also identified a number of clast types including a group with highly magnesian olivine compositions (Fo92.2-96.5). We extracted raw pixel data to investigate changes in mineralogy with depth, used QEMSCAN processors to separate and group individual clasts based on mineralogy, and determined variations in particle size with depth. Our results show a decreasing abundance of glass and agglutinate clasts with depth, associated with a higher soil maturity in the upper portion of the core. The lack of stratigraphy and dominance of non-mare clasts is consistent with the landslide origin of the material from the South Massif.

¹Hugues Leroux, ¹Pierre-Marie Zanetta, ¹Corentin Le Guillou, ²Maya Marinova
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.11.028]
¹Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 – UMET – Unité Matériaux et Transformations, F-59000 Lille, France
²Univ. Lille, CNRS, INRAE, Centrale Lille, Univ. Artois, FR 2638-IMEC-Institut Michel-Eugène Chevreul, F-59000 Lille, France
Copyright Elsevier

The study of pristine chondrites provides insight into nebular processes that occurred prior to the accretion of small-sized parent bodies. The interchondrule matrix of the primitive chondrite Acfer 094 is characterized by the presence of submicron-sized anhydrous crystalline aggregates embedded in a silicate groundmass that is mostly amorphous. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDXS) were employed to investigate the matrix of Acfer 094 and its components.
The amorphous silicate groundmass is homogeneous in composition and exhibits a Mg depletion relative to the solar value. It embeds Fe-Ni nanosulfides, whose typical size is a few tens of nanometers. Nanometer-sized fibrous silicates are rare in the groundmass indicating a low degree of aqueous alteration. Submicron-sized Mg-rich crystalline silicates (olivine and pyroxene) occur either as isolated grains or as aggregates. These submicron-sized crystalline silicates occupy around 25 % of the matrix volume. The isolated grains display a wide range of shapes, from rounded to irregularly angular, and could have originated from the fragmentation of type I chondrules or from nebular condensation. The aggregates exhibit variable morphologies and grain sizes (typically a few tens of nm). They are chemically equilibrated, and likely formed by solid-state thermal annealing of amorphous precursors.
The Acfer 094 matrix contains a range of components that have undergone varying degrees of thermal modification. A significant proportion of a precursor material (i.e. nebular dust) resembling matrix is likely to have undergone one or more brief and intense thermal events, potentially associated with the process of chondrule formation. These events resulted in the formation of magnesium-rich anhydrous silicates (forsterite and enstatite) at high temperatures that were embedded in the matrix of Acfer 094 as isolated grains and crystalline aggregates.