^1,2,3Gabriel A. Pinto,⁴Adrien Tavernier,⁵Jérôme Gattacceca,³Alexandre Corgne, ^6,7Millarca Valenzuela,¹Béatrice Luais,⁸Laura Flores,²Felipe Olivares,¹Yves Marrocchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14125]
¹CNRS, CRPG, UMR 7358, Université de Lorraine, Vandœuvre-lès-Nancy, France
²Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copiapó, Chile
³Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile
⁴IDICTEC, LICA, Universidad de Atacama, Copiapó, Chile
⁵CNRS, IRD, INRAE, CEREGE, Aix Marseille Université, Aix-en-Provence, France
⁶Millennium Institute of Astrophysics, Santiago, Chile
⁷Departamento de Ciencias Geológicas, Universidad Católica del Norte, Antofagasta, Chile
⁸Leibniz Centre for Agricultural Landscape Research, Müncheberg, Germany
Published by arrangement with John Wiley & Sons

In the last 15 years, more than 2700 meteorites have been recovered and officially classified from the Atacama Desert. Although the number of meteorites collected in the Atacama has risen, the physical and climatic properties of the dense collection areas (DCAs) have not been fully characterized. In this article, we compiled the published data of all classified meteorites found in the Atacama Desert to (i) describe the distribution by meteorite groups, (ii) compare the weathering degree of chondrites among different Atacama DCAs and other hot and cold deserts, and (iii) determine the preservation conditions of chondrites in the main Atacama DCAs in relation with the local climatic conditions. The 35 DCAs so far identified in the Atacama Desert are located in three main morphotectonic units: The Coastal Range (CR), Central Depression (CD), and Pre-Andean Range/Basement. A comparison with reported weathering data from other cold and hot deserts indicates that the mean terrestrial weathering of Atacama chondrites (W1–2), displays less alteration than other hot deserts (W2–3) and resembles the weathering distribution of the Antarctic meteorites (W1–2). The highest abundance of Atacama chondrites with low weathering (≤W2) is localized in the CD (78.8%, N = 1435), which is protected from the coastal fog influence and seasonal rainfalls and displays the oldest surfaces in the Atacama Desert. The morphogenetic classification based on present-day temperatures and precipitations of the main Atacama DCAs reveals similar regional/subregional climatic conditions in the most productive areas and a truly productive surface for meteorite recovery between 5% and 58% of the quadrangles formally defined for each Atacama DCA. Our morphogenetic classification lacks consideration of some meteorological parameters such as the coastal fog, so it cannot fully explain the differences in weathering patterns among CR chondrites. Future studies of chondrite preservation in the Atacama DCAs should consider other meteorological variables such as relative humidity, specific humidity, or dew point, in combination with exposure ages of meteorites and its surfaces.

¹Tian-Ran Trina Du,^1,2Ai-Cheng Zhang,¹Jia-Ni Chen,³Yuan-Yun Wen
American Mineralogist 109, 24–34 Link to Article[http://www.minsocam.org/MSA/AmMin/TOC/2024/Abstracts/AM109P0024.pdf]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
³Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 266071, China
Copyright: The Mineralogical Society of America

Shock lithification of regolith breccias is a ubiquitous process on the surfaces of airless planetary
bodies and may induce thermal effects, including melting on regolith breccia minerals. However, potential thermal effects on lithic and mineral clasts in regolith breccias have seldom been quantitatively
constrained. Here, we report two types of micro-textures of armalcolite [(Mg,Fe2+)Ti2O5] in an Mg-suite
lithic clast from lunar regolith breccia meteorite Northwest Africa 8182. One type of armalcolite contains
oriented fine-grained ilmenite grains; the other occurs as an aggregate of ilmenite, rutile, spinel, and
loveringite. We propose that the two types of micro-textures formed through subsolidus breakdown
of armalcolite by different processes. The formation of ilmenite inclusions in armalcolite is related to
slow cooling after the solidification of its source rock, whereas the ilmenite-rutile-spinel-loveringite
aggregates probably formed during the shock lithification event of NWA 8182. The results indicate
that the temperature at the margin of lithic clasts could be raised up to at least 600 °C during strong
shock lithification of lunar regolith and has profound thermal effects on the mineralogical and isotopic
behaviors of lithic and mineral fragments in lunar regolith breccias.

^1,2Paul Frossard,^1,3Pierre Bonnand,¹Maud Boyet,⁴Audrey Bouvier
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.12.022]
¹Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France
²Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
³Université de Bretagne Occidentale, CNRS, IFREMER, Laboratoire Géo-Océan, Plouzané, France
⁴Bayerisches Geoinstitut, Universität Bayreuth, 95447 Bayreuth, Germany
Copyright Elsevier

Mass-independent isotopic anomalies in meteorites are probes to the dynamics and evolution of the protoplanetary disc and the reservoirs from which planetary bodies accreted. Variable Cr nucleosynthetic compositions between meteorite groups are observed but the cause is not well understood. Investigations on presolar carriers in unequilibrated chondrites are thus required to establish these relationships. For that purpose, we analysed the Cr isotope compositions of leachates (stepwise dissolution solutions) of one ordinary chondrite and two enstatite chondrites of EL and EH subgroups previously measured for Nd and Sm isotopes. The leachates of the ordinary chondrite display large variations of their Cr isotope compositions, whereas the leachates of the enstatite chondrites show very limited variations of their nucleosynthetic compositions, confirming other studies. The Cr isotope compositions of leachates of unequilibrated chondrites are significantly modified by thermal processing and aqueous alteration under various conditions. The leachates of the enstatite chondrites are relatively homogeneous for Cr isotope composition, suggesting that presolar carriers of Cr are not stable under very reduced conditions and are likely oxidised phases. After careful examination of the role of parent body processing, we conclude that there is one predominant presolar carrier enriched in 54Cr that produced most of the nucleosynthetic variations observed in leachates. This carrier is likely depleted in the carbonaceous reservoir relative to the non-carbonaceous reservoir. The drastically different isotope compositions of Cr and heavy refractory lithophile elements such as Nd of leachates of chondrites reflect relative preservation biases of their respective presolar carriers, namely a still poorly characterised presolar oxide and silicon carbide (SiC), respectively.