^1,2E.S. Steenstra, ^1,3C.J. Renggli, ¹J. Berndt, ¹S. Klemme
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.08.021]
¹Institute of Mineralogy, University of Münster, Germany
²Faculty of Aerospace Engineering, Technische Universiteit Delft, the Netherlands
³Max Planck Institute for Solar System Research, Göttingen, Germany
Copyright Elsevier

The processes responsible for the isotopic compositions and abundances of volatile elements in the early solar system remain highly debated. Orders of magnitude variation of (highly) volatile elements exist between different magmatic iron meteorite groups, but it is unclear to what extent their depletions can be explained by evaporation from metal melts during parent body accretion and/or subsequent break up. To this end, we present 86 new evaporation experiments with the aim of constraining the volatility of most volatile metals from metallic melts. The results confirm the previously proposed important effects of S in metal melt on the volatility of the elements of interest governed by their S-loving or S-phobic behavior. Nominally S-loving elements In, Sn, Te, Pb and Bi are significantly more volatile in Fe melt relative to FeS liquid, whereas nominally S-avoiding elements Ga and Sb are more volatile in FeS liquid relative to Fe melt, at a given pressure and temperature. The newly derived volatility sequences for S-free/poor and S-rich metallic melts were also compared with commonly used volatility models based on condensation temperatures. The results indicate significant differences between the latter, including the much more volatile behavior of Te, relative to Se, in both explored bulk compositions, which are traditionally assumed to be equally volatile. The (minimum) degree of volatile element depletion due to evaporation was quantified using the new experimental results and models. A comparison between the volatile element depletions in magmatic iron meteorites and the predicted depletions appropriate for evaporation from Fe melts shows that the latter depletions can be easily reconciled with (an) evaporation event(s). Altogether, the new data and models will provide an important framework when more accurate and precise estimates of magmatic iron meteorite bulk volatile element contents are available.

^1,2A. Musolino,^1,3M. D. Suttle,^1,4L. Folco,⁵A. J. King,^6,7G. Poggiali,⁵H. C. Bates,⁶J. R. Brucato,⁸A. Brearley
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14261]
¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
²Aix-Marseille Université, CEREGE, CNRS, IRD, Aix-en-Provence, France
³School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK
⁴CISUP, Centro per l’Integrazione della Strumentazione dell’Università di Pisa, Pisa, Italy
⁵Planetary Materials Group, Natural History Museum, London, UK
⁶INAF-Astrophysical Observatory of Arcetri, Florence, Italy
⁷LESIA-Observatoire de Paris, PSL University, Paris, France
⁸UNM, Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Published by arrangement with John Wiley & Sons

Reckling Peak (RKP) 17085 is a newly classified Antarctic CM chondrite that preserves a complex alteration history characterized by mild aqueous alteration (CM2.7), overprinted by a short-lived thermal metamorphic event (heating stage III [<750°C]), and affected by low-grade terrestrial weathering. This meteorite contains abundant Fe-rich bands within the fine-grained matrix, composed of micron-scale Fe-oxyhydroxide minerals. They are interpreted as “alteration fronts” arising due to the dissolution and transport of Fe (typically <500 μm) before being abruptly deposited. This alteration texture is relatively rare among hydrated carbonaceous chondrites, with only five reported instances to date (Murchison, Murray, Allan Hills 81002, Miller Range 07687, and Northwest Africa 5958). Evidence from RKP 17085 suggests that early aqueous alteration operated as multiple geochemically isolated microenvironments, which moved outwards from local point sources within the matrix. Low permeability fine-grained rims on chondrules appear to have acted as barriers to fluid flow, controlling the migration of fluid across the parent body. Furthermore, the higher porosity regions within the altered fine-grained matrix represent either void space generated by the dehydration of hydrated minerals during post-hydration metamorphism and/or sites of ice accretion (water-ice or C-bearing ices) preserved within a mildly altered primitive matrix.

¹Martin R. Lee,^1,2,3Luke Daly,¹Jennika Greer,¹Sammy Griffin,¹Cameron J. Floyd,²Levi Tegg,³Julie Cairney
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14253]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
²Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales, Australia
³ Department of Materials, University of Oxford, Oxford, UK
Published by arrangement with John Wiley & Sons

Many of the CM carbonaceous chondrites are regolith breccias and so should have abundant evidence for collisional processing. The constituent clasts of these fragmental rocks frequently display compactional petrofabrics; yet, olivine microstructures show that most CMs are unshocked. To better understand the reasons for this contradiction, we have sought other evidence for hypervelocity impact processing of CM chondrites using the Cold Bokkeveld meteorite. We find that this regolith breccia contains rare particles of vesicular shock melt that are close in chemical composition to bulk CM chondrite. Transmission electron microscopy of a melt bead shows that it is composed of silicate glass with inclusions of pentlandite, pyrrhotite, and wüstite. Characterization of shards of another bead by atom probe tomography reveals nanoscale clusters of sulfur that represent sulfide inclusions arrested at an early stage of growth. These glass particles are mineralogically comparable to micrometeoroid impact melt described from the Cb-type asteroid Ryugu and melt that has been experimentally produced by pulsed laser irradiation of CM targets. The glass could have formed by in situ shock-melting, but petrographic evidence is more consistent with an origin as ballistic ejecta from a distal impact. The scarcity of melt in this meteorite, and CM chondrites more broadly, is consistent with the explosive fragmentation of hydrous asteroids following energetic collisions. Cold Bokkeveld’s parent body is likely to be a second-generation asteroid that was constructed from the debris of one or more earlier bodies, and only a small proportion of the reaccreted material had been highly shocked and melted.

¹A. N. Nguyen,²S. J. Clemett,³K. Thomas-Keprta,⁴C. M. O’D. Alexander,⁵D. P. Glavin,⁵J. P. Dworkin,^6,7,8H. C. Connolly Jr,⁸D. S. Lauretta
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14254]
¹Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA
²ERC, Inc., JETS/Jacobs, Houston, Texas, USA
³Barrios, JETS/Jacobs, Houston, Texas, USA
⁴Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
⁵Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
⁶Department of Geology, School of Earth and Environment, Rowan University, Glassboro, New Jersey, USA
⁷Department of Earth and Planetary Science, American Museum of Natural History, New York, New York, USA
⁸Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

Samples of B-type asteroid (101955) Bennu returned by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft will provide unique insight into the nature of carbonaceous asteroidal matter without the atmospheric entry heating or terrestrial weathering effects associated with meteoritic samples. Some of the Bennu samples will undergo characterization by X-ray computed tomography (XCT). To protect the pristine nature of the samples, it is important to understand any adverse effects that could result from irradiation during XCT analysis. We analyzed acid-insoluble residues produced from two powdered samples of the Murchison carbonaceous chondrite, one control and one XCT-scanned, to assess the impact on insoluble organic matter (IOM) and presolar grains. Using a suite of in situ analytical techniques (field-emission scanning electron microscopy, optical and ultraviolet fluorescence microscopy, microprobe two-step laser mass spectrometry, and nanoscale secondary ion mass spectrometry), we found that the two residues had indistinguishable chemical, molecular, and isotopic signatures on the micron to submicron scale, indicating that an X-ray dosage of 180 Gy (the maximum dose to be used during preliminary examination of Bennu materials) did not damage the IOM and presolar grains. To explore the use of acid-insoluble residues to infer parent body processes in preparation for Bennu sample analysis, we also analyzed a residue produced from the Sutter’s Mill carbonaceous chondrite. Multiple lines of evidence, including severely degraded UV fluorescence signatures and D-rich hotspots, indicate that the parent body of Sutter’s Mill was heated to >400°C. This heating event was likely short lived because the abundance of presolar SiC grains, which are destroyed by thermal metamorphism and prolonged oxidation, was consistent with those in Murchison and other unheated chondrites. The results of these in situ analyses of acid-insoluble residues from Murchison and Sutter’s Mill provide complementary detail to bulk analyses.

^1,2V. P. Singh,^1,2N. G. Rudraswami,^3,4Nittala V. Chalapathi Rao,⁵Matthew J. Genge,¹M. Pandey,^1,2S. Sreekuttan,³S. Chattopadhaya
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14256]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, India
²Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
³Department of Geology, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India
⁴National Centre for Earth Science Studies, Ministry of Earth Sciences, Thiruvananthapuram, India
⁵Department of Earth Science and Engineering, Imperial College London, London, UK
Published by arrangement with John Wiley & Sons

The Cretaceous–Paleogene (K-Pg) boundary represents the extinction of ~70% of species, a prominent Chicxulub impact event and Deccan volcanism. This work reports the first attempt to extract the micrometeorites (MMs) from the Deccan intertrappean horizons. Eighty-one spherical particles were studied for their morphological, textural, and chemical characteristics. Intact cosmic spherules with ferromagnesian silicates (6) and Fe-Ni oxide (7) compositions correspond to MMs from the deep sea and Antarctica. Silicate and Fe-Ni spherules in this study showcase remarkable preservation, a testament to the highly favorable conditions present. Fe spherules (38) with iron oxide compositions exhibit diagenetic alteration during preservation. Textural analysis of 30 Fe spherules reveals a dendritic, interlocking pattern and slightly elevated Mn content, suggesting these may be fossilized I-type MMs. However, eight Fe spherules with blocky and cubical granular textures resemble oxidized pyrite spherules. Al-Fe-Si spherules (30) possess a significant enrichment of Al and Si within their Fe-oxide-dominated composition. Group-I Al-Fe-Si spherules (15) display zoned Al-Fe-Si oxide composition, dendritic Mg-Cr spinel grains, and aerodynamic features, all indicative of impact spherules. The finding of these impact spherules from sampled Deccan intertrappean layer raises the possibility that these paleosols were deposited during the Chicxulub impact event, the only identified impact event with global distribution during the Deccan volcanism time frame. This unique location provides an opportunity for the simultaneous collection of well-preserved MMs, impact, and volcanic spherules. The exceptional preservation of the studied MMs is likely due to a combination of non-marine environments, atypical climatic conditions, and rapid deposition. This study further investigates the potential role of cosmic dust flux in the K-Pg extinction event. We propose that the enhanced cosmic dust flux, a likely scenario during the K-Pg boundary period, synergistically mixing with impact dust in the upper atmosphere, may have intensified and extended the harsh climatic conditions at the K-Pg boundary. Subsequently, the deposition of this dust, enriched in bioavailable iron, on Earth’s surface might have contributed to the swift recovery of life and environmental conditions.

^1,2Y. Srivastava,¹A. Basu Sarbadhikari,³A. Yamaguchi,⁴A. Takenouchi,⁵J. M. D. Day,⁶T. Ubide
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14257]
¹Physical Research Laboratory, Ahmedabad, India
²Indian Institute of Technology, Gandhinagar, Gujarat, India
³National Institute of Polar Research (NIPR), Tokyo, Japan
⁴The Kyoto University Museum, Kyoto University, Kyoto, Japan
⁵Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
⁶School of the Environment, The University of Queensland, Brisbane, Queensland, Australia
Published by arrangement with John Wiley & Sons

Lunar basaltic meteorite Asuka-881757 (A-881757), a member of the source crater paired YAMM meteorites (Yamato-793169, A-881757, Miller Range 05035 and Meteorite Hills 01210), provides information on potassium-rare earth element-phosphorous (KREEP)-free magmatic sources within the Moon. Asuka-881757 is an unbrecciated and Fe-rich (Mg# 36) gabbro with coarse pyroxene (2–8 mm) and plagioclase (1–3 mm). The coarse pyroxene preserves mm-scale, near-complete hour-glass sector zoning with strong Ca and Fe partitioning, similar to some Fe-rich Apollo basalts. In contrast to the most Mg-rich Apollo basalts, A-881757 contains various types of symplectites (~8 vol%) formed by the breakdown of pyroxferroite due to slow cooling, resembling a few extreme Fe-rich (Mg#
40) Apollo basalts. Petrographic observations and thermodynamic modeling suggest crystallizing in the order: Fe-poor pyroxenes (Mg# 58–55) → co-crystallized plagioclase and Fe-rich pyroxenes (Mg# 49–20) → late-stage assemblage including Fe-augite, Fayalite, and Fe-Ti oxides. Combining phase stability at variable P–T with petrographic observations, the minimum depth of formation of the A-881757 parent magma can be constrained to between 60 and 100 km. KREEP-free basalts (such as A-881757 and the YAMM meteorites) originated from a relatively shallow mantle source and later underwent polybaric crystallization that occurred prior to eruption at the lunar surface. In contrast, the Apollo mare basalts mostly crystallized within lava flows from relatively deeper-seated mantle sources. The crystallization of A-881757 and other YAMM meteorites is unlike most Apollo basalts from the Procellarum KREEP terrane, and likely represent hidden cryptomare basalts close to lunar surface.

¹Mengyan Zheng,^1,2Yoko Kebukawa,¹Yuka Hayashi,¹Kensei Kobayashi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14259]
¹Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, 240-8501 Yokohama, Japan
²Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, 152-8551 Tokyo, Japan
Published by arrangement with John Wiley & Sons

CI, CM, and CR carbonaceous chondrites contain hydrous minerals, indicating that their parent bodies underwent aqueous alteration at low temperatures. Some of these chondrites, such as heated CM, CI, and CY chondrites, experienced thermal dehydration by impacts or solar radiation after aqueous alteration. This study conducted heating experiments on carbonaceous chondrites and evaluated their dehydration/dehydroxylation kinetics in an effort to explain the thermal history of the parent asteroids of heated carbonaceous chondrites using their degrees of dehydration/dehydroxylation of hydrous minerals. Murchison (CM2.5) and Ivuna (CI1), relatively primitive (having not undergone thermal alteration) carbonaceous chondrites, were used as starting materials. Weakening in the OH band at ~3680 cm−1 (2.72 μm) with isothermal heating at 350–500°C (Murchison) and 450–525°C (Ivuna) were observed under in situ infrared spectroscopy (FT-IR) equipped with a heating stage. To determine the rate constants, the decrease in the OH band was fitted using kinetic models such as first-order reactions, two-dimensional diffusion, and three-dimensional diffusion. The apparent activation energies and frequency factors were determined using the Arrhenius equation. Time–temperature transformation diagrams were drawn to represent the decrease in the OH-band intensity as a function of temperature and heating duration. Such kinetic approaches can provide constraints on the temperature and time of the dehydration/dehydroxylation processes and enable us to estimate long-term effects from experiments in the laboratory within a short time.

¹Christopher J.-K. Yen et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14260]
¹Department of Earth and Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 12384 is a lunar polymict breccia composed almost entirely of basaltic components. The clast content includes low- to very-low-Ti volcanic picritic glass, basaltic vitrophyre, and crystalline pigeonite basalt—an assemblage of volcanic materials that can be tested for petrogenetic relationships. We present the inferred history of select mare components of NWA 12384 as suggested by texture, mineralogy, and petrography, and compare them to Apollo samples and other lunar meteorites. In addition, we used the volcanic glasses in the breccia as a primary composition for crystallization modeling and comparison to the lithic clast compositions. We find that the mafic clasts in NWA 12384 cannot be derived from the picritic glass through a common liquid line of descent because of higher Ti content, though they may have crystallized from a separate, common liquid line of descent. These clasts could represent local source-region heterogeneity or differential assimilation of more Ti-rich material. Pb-Pb SIMS analyses of a large basalt clast in NWA 12384 reveal an age of 3044 ± 41 Ma (2σ), which is used together with the chemical data and 4π cosmic ray exposure age of less than 20 kyr and terrestrial age of between 3.1 and 17.3 kyr to constrain the possible locations of provenance for this meteorite.

¹van Kooten, Elishevah,²Zhao, Xuchao,²Franchi, Ian,³Tung, Po-Yen,³Fairclough, Simon,³Walmsley, John,¹Onyett, Isaac,¹Schiller, Martin,^1,4Bizzarro, Martin
Science Advances 10, eadp1613 Open Access Link to Article [DOI 10.1126/sciadv.adp1613]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, Copenhagen, 1350, Denmark
²School of Physical Sciences, Open University, Milton Keynes, MK7 6AA, United Kingdom
³Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, United Kingdom
⁴Institut de Physique du Globe de Paris, Université Paris Cité, 1 Rue Jussieu, Paris, 75005, France

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¹Hausrath E.M. et al. (>10)
Minerals 14, 591 Open Access Link to Article [DOI 10.3390/min14060591]
¹Department of Geoscience, University of Nevada, Las Vegas, 89154, NV, United States

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