^1,2,3,4S.N. Valencia,¹R.L. Korotev,¹B.L. Jolliff
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.12.034]
¹Department of Earth & Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University in St.Louis, St. Louis, MO 63130
²Department of Astronomy, University of Maryland, College Park, MD 20742
³NASA Goddard Space Flight Center, Greenbelt, MD 20771
⁴Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD 20771
Copyright Elsevier

We report bulk rock composition and mineral chemistry of previously unstudied fragments and thin sections of lunar granitic breccia 12013. Instrumental Neutron Activation Analysis data on 25 fragments indicate that the 12013 breccia can be described as a three-component system comprising granitic, rare earth element (REE)-rich, and mafic components. The granitic component is low in FeO and REE but rich in K2O, Th, and associated incompatible elements. The REE-rich component has an elevated concentration of REE, moderate FeO, and low concentrations of those elements that are high in the granitic component, in other words, its composition is complementary to that of the granitic component. The mafic component is richest in FeO, and low in those elements that are concentrated in the granitic and REE-rich components. Petrographically, the REE-rich component is an impact melt breccia with a composition unique to Apollo 12 impact melt breccias. Trace-element concentrations in the REE-rich component indicate that its protolith is possibly monzogabbro, although its composition is significantly more magnesian than other known lunar monzogabbros. The mafic component is dominated by fine-grained pyroxene and plagioclase that appear to have recrystallized after impact. However, preserved lithic clasts with an igneous texture occur in the mafic component and are inferred to represent its protolith. The textures of the preserved mafic lithic fragments and lack of Mg-Fe zoning in pyroxene indicate that the protolith of the mafic component formed either as a crustal intrusion or at the bottom of a thick lava flow. The composition of the mafic component is unlike any previously studied mare basalt samples. Textures of this complex breccia suggest that the granitic breccia was first incorporated with the mafic component to form the “gray breccia”, and that the gray breccia was then incorporated with the REE-rich component while the components were still in a hot, plastic state. The complementary trace-element compositions, including the REE patterns, indicate that the petrogenesis of the granitic and REE-rich components are related. We infer that silicate-liquid immiscibility is likely not the formation mechanism for the 12013 components. Instead, bimodal volcanism owing to basaltic underplating may have led to the formation of the 12013 components.

^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.

During the last days of this year, Cosmochemistry Papers will be on Christmas break. Normal service will commence on January, 2nd, 2024 .

Merry Christmas & Happy New Year to everyone!

¹Takaharu Saito,¹Hiroshi Hidaka,²Shigekazu Yoneda
The Astrophysical Journal 955, 85 Open Access Link to Article [DOI 10.3847/1538-4357/acf37b]
¹Department of Earth and Planetary Sciences, Nagoya University, Nagoya 464-8601, Japan; ²Department of Science and Engineering, National Museum of Nature and Science, Tsukuba 305-0005, Japan

The isotopic compositions of Sm and Gd in eight eucrites—five from a desert, Dar al Gani (DaG) 380, DaG 391, DaG 411, DaG 443, and DaG 480, and three from nondesert areas, Juvinas, Millibillillie, and Stannern—were determined to understand the cosmic-ray exposure (CRE) history for each meteorite from the isotopic shifts of 149Sm–150Sm and 157Gd–158Gd caused by the neutron capture reactions induced by cosmic-ray irradiation. Seven of the eight samples, excepting DaG 443, show readily detectable isotopic shifts of Sm and Gd corresponding to neutron fluences in the range of (0.28–2.38) × 1015 neutrons cm−2. The degrees of Sm isotopic shifts for six of these seven eucrites can be consistently explained by the CRE age histogram of eucrites obtained in previous studies. Exceptionally, DaG 480 shows larger isotopic shifts of Sm than those expected from the CRE age histogram, suggesting a multiple-irradiation history, including irradiation on the parent body. However, there is no clear difference in the CRE conditions between DaG 480 and other eucrites from the parameter εSm/εGd to identify the difference in the thermalization degree of neutrons in association with the CRE conditions.

¹Kurt Marti,²Mario Fischer-Gödde,³Carina Proksche
The Astrophysical Journal 956, 7 Open Access Link to Article [DOI 10.3847/1538-4357/acee81]
¹Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0314, USA
²Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, D-50674 Köln, Germany; mfisch48@uni-koeln.de
³Geo Zentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 5, D-91054 Erlangen, Germany

Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s-process component. We report isotopic relations of ⁹²Mo versus ¹⁰⁰Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s-process abundance variations. We show that two p-process isotopes ⁹²Mo and ⁹⁴Mo require the presence of distinct p-process components in meteoritic materials. The nucleosynthetic origin of abundant magic (N = 50) p-process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp-antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p-process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p-nuclides.

^1,4Oshtrakh, Michael I.,^1,2Maksimova, Alevtina A.,¹Petrova, Evgeniya V.,¹Chukin, Andrey V.,³Felner, Israel
Hyperfine Interactions 244, 22 Link to Article [DOI 10.1007/s10751-023-01830-9]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
²Department of Chemistry and Biochemistry, University of South Carolina, Columbia, 29208, SC, United States
³Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel
⁴Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation

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¹Unsalan, Ozan,²Yilmaz, Berguzar,³Reva, Igor
ACS Earth and Space Chemistry 7, 1992 – 2005 Link to Article [DOI 10.1021/acsearthspacechem.3c00108]
¹Faculty of Science, Department of Physics, Ege University, Izmir, Bornova, 35100, Turkey
²Natural and Applied Sciences, Department of Biotechnology, Ege University, Izmir, Bornova, 35100, Turkey
³CIEPQPF, Department of Chemical Engineering, University of Coimbra, Rua Sílvio Lima, Coimbra, 3030-790, Portugal

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¹Jonatan Michimani,¹Eduardo Rondón,²Davide Perna,²Simone Ieva,²Elisabetta Dotto,²Elena Mazzotta Epifani,^3,4Antonella Barucci,²Vasiliki Petropoulou,²Daniela Lazzaro
Monthly Notices of the Royal Astronomical Society 526, 2067–2076 Link to Article [https://doi.org/10.1093/mnras/stad2883]
¹Observatório Nacional, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
²INAF – Osservatorio Astronomico di Roma, Via Frascati 33, I-00078, Monte Porzio Catone, Italy
³LESIA, Observatoire de Paris, PSL Research University, CNRS,
⁴Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Univ., Paris 06, Sorbonne Universités, 5 Place J. Janssen, F-92195 Meudon Pricipal Cedex, France

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