¹B. Bultel,²M. Wieczorek,³Anna Mittelholz,^4,5Catherine L. Johnson,⁶Jérôme Gattacceca,^7,8,9Valentin Fortier,¹⁰Benoit Langlais
Journal of Geophyisical Research (Planets) Open Access Link to Article [https://doi.org/10.1029/2023JE008111]
¹GEOPS, Université Paris-Saclay, CNRS, Orsay, France
²Institut de Physique du Globe de Paris, Université Paris Cité, CNRS, Paris, France
³Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland
⁴University of British Columbia, Vancouver, BC, Canada
⁵Planetary Science Institute, Tucson, AZ, USA
⁶Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
⁷Université Catholique de Louvain-la-Neuve, Earth and Life Institute, Louvain-la-Neuve, Belgium
⁸Laboratoire G-Time, Université Libre de Bruxelles, Bruxelles, Belgium
⁹Géosciences Montpellier, CNRS, Univ. Montpellier, Montpellier, France
¹⁰ de Planétologie et Géosciences UMR 6112, Nantes Université, Univ Angers, Le Mans Université, CNRS, Nantes, France
Published by arrangement with John Wiley & Sons

Strong magnetic fields have been measured from orbit around Mars over parts of the ancient southern highlands crust and on the surface at the InSight landing site. The geological processes that are responsible for generating strong magnetization within the crust remain poorly understood. One possibility is that intense aqueous alteration of crustal materials, through the process of serpentinization, could have produced magnetite that was magnetized in the presence of a global core-generated magnetic field. Here, we test this idea with geophysical and geochemical models. We first determine the magnetizations required to account for the observed magnetic field strengths and then estimate the amount of magnetite necessary to account for these magnetizations. For the strongest orbital magnetic field strengths, about 7 wt% magnetite is required if the magnetic layer is 10 km thick. For the surface field strength observed at the InSight landing site, 0.4–1.1 wt% magnetite is required if the magnetic layer corresponds to one or more of the three crustal layers observed in the InSight seismic data (with thicknesses from 8 to 39 km). We then investigate the minerals that are produced by aqueous alteration for various possible crustal compositions and water-to-rock ratios using a thermodynamic model. Magnetite abundances up to 6 wt% can be generated for dunitic compositions that could account for the strongest magnetic anomalies. For more representative basaltic starting compositions, however, more than 0.4 wt% can only be generated when using high water-to-rock ratios, which could account for the weaker magnetizations beneath the InSight landing site.

¹J. N. Levin,¹A. J. Evans,²J. C. Andrews-Hanna,¹I. J. Daubar
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008418]
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
²Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd Tucson AZ, Tucson, AZ, USA
Published by arrangement with John Wiley & Sons

The distribution of KREEP—potassium (K), rare earth elements (REE), and phosphorus (P)—in the lunar crust is an important clue to deciphering the geochemical and thermal evolution of the Moon. Surface measurements of thorium abundance taken by the Lunar Prospector Gamma Ray Spectrometer (LP GRS) instrument have shown that KREEP is concentrated on the lunar nearside surface, mirroring the hemispheric asymmetry observed in the distribution of maria, crustal thickness, and topography. However, the overall lateral and vertical distribution of KREEP within the crust is poorly constrained, leaving uncertainty in estimates of bulk crustal thorium abundance and in the history and evolution of KREEP. In this study, we compared the overall lateral and vertical distribution of lunar KREEP in the upper crust by determining the thorium abundance of material excavated by complex impact craters. We find that the distribution of KREEP on the nearside is consistent with a layer of high-Thorium ejecta from the Imbrium impact mixing with underlying low-Th (<1 ppm) crustal material, suggesting the excavation of a sub-crustal KREEP reservoir with thorium abundances as high as 45–120 ppm by the Imbrium-forming impact. Imbrium ejecta alone does not explain the distribution of thorium on the lunar farside, particularly around the South Pole Aitken basin, suggesting other sources for farside thorium enrichments. Furthermore, our results refute the existence of a large-scale Thorium-enriched layer in the upper 16 km of the farside crust.

¹T.J.McCoy et al. (>10)
Nature 637, 1072-1077 Open Access Link to Article [DOI https://doi.org/10.1038/s41586-024-08495-6]
¹Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA

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¹D. S. Burnett et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14313]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
Published by arrangement with John Wiley & Sons

Solar wind Fe and Mg fluences (atoms/cm2) were measured from Genesis collectors. Fe and Mg have similar first ionization potentials and solar wind Fe/Mg should equal the solar ratio. Solar wind Fe/Mg is a more valid measure of solar composition than CI chondrites and can be measured more accurately than spectroscopic photospheric abundances. Mg and Fe fluences analyzed in four laboratories give satisfactory agreement. Si and diamond-like carbon collector fluences agree for both elements. The Mg and Fe fluences are 1.731 ± 0.073 × 1012 and 1.366 ± 0.058 × 1012 atoms/cm2. All plausible sources of errors down to the 1% level are documented. Our value for the solar system Fe/Mg, 0.789 ± 0.048 agrees within 1 sigma errors with CI chondrites, spectroscopic photospheric abundances, and with the solar wind data from the ACE spacecraft. CI samples from asteroid Ryugu give Fe/Mg in agreement with Genesis and meteoritic CI samples despite very small sample sizes. The higher accuracy of the Genesis solar Fe/Mg permits a comparison with chondritic Fe/Mg at the 10% level. Intermeteorite Fe/Mg averages differ among the main C chondrite groups but are within, or very close to, the ±1 sigma Genesis solar Fe/Mg.

¹B. H. Oliveira,¹J. F. Snape,¹R. Tartèse,¹J. F. Pernet-Fisher,²D. van Acken,³M. J. Whitehouse,¹K. H. Joy
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14305]
¹Department of Earth and Environmental Sciences, University of Manchester, Manchester, UK
²UCD School of Earth Sciences, University College Dublin, Dublin, Ireland
³Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
Published by arrangement with John Wiley & Sons

The Calcalong Creek lunar meteorite is a regolith breccia with a lithologically diverse array of clasts set in a glassy, highly vesicular matrix. Here, we present a comprehensive new analysis of the meteorite. Comparisons to remote sensing data, lunar sample lithologies, and lunar sample ages indicate that it was likely sourced from regolith surrounding the Moon’s nearside Procellarum KREEP Terrane, as opposed to the farside South Pole-Aitken basin as has been previously suggested. Partial and complete reset dates of ~3.9 Ga suggest a disturbance at this time, which aligns with that of the Imbrium basin-forming event, and to a lesser degree we see evidence of a ~4.2 Ga impact, which may be related to the formation of the Serenitatis basin. Analysis of Calcalong Creek clasts, thus, provide insights not only on the timing of major impact basin formation but also on the volcanic history of the Moon. The meteorite also samples some ancient ~4.3 Ga evolved magmatism, manifested in the presence of granophyre clasts, which may have originated from a high-μ, KREEP-like source, as well as younger, ~3.7 Ga low-Ti basaltic magmatism.

¹M.E.I.Riebe et al.(>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.01.034]
¹Institute of Geochemistry and Petrology, ETH Zürich, CH-8092 Zürich, Switzerland
Copyright Elsevier

Most ureilites are melt residues from the partially melted Ureilite Parent Body. The Ureilite Parent Body was catastrophically disrupted at ∼ 5 Ma after CAI while it was still hot and the ureilites provide a unique window into early solar system magmatic processing. One ureilitic trachyandesite, one cumulate, and 16 melt residue ureilites, all from the Almahata Sitta meteorite strewn field, were analyzed for their noble gas compositions and, when such data was unavailable, for oxygen isotopes and petrology. Additionally, ureilite noble gas data from the literature was compiled together with petrology and oxygen isotope data of the same samples, this data is available in the supplementary materials. The compositions of noble gases and oxygen, as well as petrological characteristics, are similar to previously analyzed ureilites. This includes variable 36Artr/132Xe ratios of ∼ 20–––1000 correlated with variable 84Kr/132Xe ratios of ∼ 0.15–––2.5 and Xe isotopic compositions similar to the Q gases but with somewhat lower 134,136Xe/132Xe ratios. The well-established correlation between Mg-Fe olivine core composition and Δ’17O, interpreted as material mixing, is corroborated. There is no correlation between noble gas compositions and petrology or Δ’17O. Therefore, it is unlikely that the variable noble gas elemental ratios are due to mixing of noble gases from different sources, as previously suggested. We suggest that compositional variability was established during implantation of noble gases into disordered carbon prior to accretion and possibly during later processing. We discuss that partial graphitization resulted in noble gas loss, with noble gases remaining in un-graphitized organics, which were converted to diamond during the catastrophic disruption. Noble gases released during graphitization may have entered the melt. Isotopic compositions of trapped noble gases in the cumulate and trachyandesitic rocks, which crystallized from the melt are similar to those in the melt residue ureilites. The elemental noble gas composition of the cumulate shows evidence of a degassing stage and that the concentrations of noble gases in the ureilites were higher before melting. The noble gases in the trachyandesite contains radiogenic noble gases from decay of K, I, Th, and U, which were not enriched in the cumulate, showing that the trachyandesite crystallized from a more evolved melt. The cosmic-ray exposure ages of 15–––22 Ma, with mostly overlapping uncertainties, are similar to those previously determined for ureilites from the Almahata Sitta strewn field and display a limited spread in contrast to ages previously detected in Almahata Sitta chondrites.

¹Alexander N. Krot, ¹Kazuhide Nagashima, ²Tasha L. Dunn, ³Chi Ma, ⁴Michail I. Petaev
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.01.027]
¹Hawai‘i Institute of Geophysics & Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
²Department of Geology, Colby College, Waterville, ME 04901, USA
³Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
⁴Department of Earth & Planetary Sciences, Harvard University, Cambridge MA 02138, USA
Copyright Elsevier

We report on oxygen and aluminum-magnesium isotope systematics of Compact Type A (CTA), Type B (B), and Forsterite-bearing Type B (FoB) Ca,Al-rich inclusions (CAIs) from the Northwest Africa (NWA) 5343 (CK3.7) and NWA 4964 (CK3.8) chondrites that experienced metasomatic alteration in the presence of aqueous solution that resulted in replacement of primary melilite, AlTi-diopside, grossmanite, anorthite, and perovskite by secondary minerals. The primary minerals have excesses of radiogenic 26Mg (26Mg*) that correlate with 27Al/24Mg ratio; the only exception is melilite in the CTA CAI. The calculated internal Al-Mg isochrons in the CTA (excluding melilite), Type B, and FoB CAIs correspond to the initial 26Al/27Al ratios [(26Al/27Al)0] of (5.09 ± 0.58) × 10−5, (2.58 ± 3.2) × 10−5, and (5.05 ± 0.66) × 10−5, respectively. The gehlenitic melilite (Åk<1) in the CTA CAI has resolvable 26Mg* but very high 27Al/24Mg (up to ∼ 660) and does not belong to the internal isochron defined by hibonite, spinel, and grossmanite. The high 27Al/24Mg in melilite containing submicron inclusions of grossular is due to redistribution of Mg between these minerals during thermal metamorphism. Hibonite, spinel, forsterite, rhönite/louisfuchsite, and a grossmanite inclusion in spinel have 16O-rich compositions (Δ17O ∼  − 23 ± 2 ‰), whereas melilite, anorthite, and perovskite are 16O-poor (Δ17O ∼  − 3 ± 2 ‰). Grossmanite and AlTi-diopside are 16O-depleted to various degrees: Δ17O ranges from ∼  − 24 to ∼  − 3 ‰; the degree of 16O-depletion correlates with titanium content in pyroxene. On a three-isotope oxygen diagram secondary grossular, FeAl-diopside, FeMg-olivine, and plagioclase plot along mass-dependent fractionation line with Δ17O of ∼  − 3.7 ± 1.9 ‰ that corresponds to Δ 17O of metasomatic fluid in the host meteorites. This value is indistinguishable from Δ 17O of metasomatic fluid that resulted in alteration of Allende (CV > 3.6) CAIs.
Coarse-grained igneous CAIs in CKs and CVs have similar size distribution, textures and primary mineralogy, formed in a gas of approximately solar O-isotope composition (Δ 17O ∼  − 24 ± 2 ‰) and had the canonical (26Al/27Al)0, suggesting they belong to the same generation of refractory inclusions, further supporting genetic relationship between CVs and CKs. Oxygen-isotope heterogeneity in CV > 3.6 and CK3.7 − 3.8 CAIs resulted from postcrystallization O-isotope exchange with 16O-depleted metasomatic fluid (Δ 17O ∼  − 3.7 ± 1.9 ‰) on their parent asteroid(s). This exchange preferentially affected melilite, anorthite, perovskite, and AlTi-pyroxenes, whereas hibonite, spinel, rhönite/louisfuchsite, and forsterite retained their original 16O-rich compositions established during igneous crystallization in a gas of approximately solar composition. Metasomatic alteration and thermal metamorphism of CAIs from CK3.7 − 3.8 and CV > 3.6 chondrites disturbed their Al-Mg isotope systematics to various degrees.

¹A.Galiano et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14315]
¹INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy
Published by arrangement with John Wiley & Sons

The spectral analysis of CM meteorites can help to constrain the mineralogical composition of their parent body, the C-type asteroids. The CM2 NWA 12184 was spectrally examined employing seven complementary techniques at different spatial resolutions, including VIS-to-MIR reflectance and Raman spectroscopy. Furthermore, the effects of space weathering on asteroids can be investigated by performing laboratory simulations on meteorites samples; thus, the meteorite was processed with He+ ions at 200 keV (maximum fluence of 1.0 × 1017 ions cm−2) to simulate the solar wind irradiation on C-type asteroids. We discriminated the mineralogical composition of the NWA 12184 at the millimeter scale and at the micrometer scale, investigating both matrix and chondrules. The ion experiment produced spectral darkening, reddening, shifting of the hydration band, and weakening of the absorption band ascribed to olivine in the VIS-NIR range, as well as the reduction in the olivine’s peak in MIR range, clue of the sample’s amorphization. The study identified the native mineralogy of the meteorite, the products of terrestrial weathering, and the aqueous and thermal alteration experienced by the parent body of the sample.

¹Kakeru Kukihara,¹Masaaki Miyahara,²Akira Yamaguchi,³Yoshio Takahashi,^4,5Yasuo Takeichi,⁶Naotaka Tomioka,⁷Eiji Ohtani
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14316]
¹Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Japan
²National Institute of Polar Research, Tokyo, Japan
³Department of Earth and Planetary, Graduate School of Science, The University of Tokyo, Tokyo, Japan
⁴Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Japan
⁵School of Engineering, Osaka University, Osaka, Japan
⁶Kochi Institute for Core Sample Research, X-star, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Japan
⁷Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

The petrologic and mineralogical characteristics and alteration processes of the nakhlites NWA 6148 and NWA 10153 were studied. Both consist of augite, olivine, and mesostasis. Based on the characteristics of each volume fraction of the components and the chemical composition of olivine and pyroxene, NWA 6148 correspond to lava units crystallized at 1346–1391 Ma in the nakhlite body. The position of NWA 10153 in the nakhlite body is unclear. Iron oxides/hydroxides, barite, and calcite fill the fractures of NWA 6148, which are terrestrial weathering products. In NWA 10153, olivine grains are replaced by goethite, magnetite, saponite, amorphous silica, jarosite, and siderite. Although it is uncertain whether all of the alteration minerals were formed on the surface of Mars or on the surface of Earth, NWA 10153 records two different alteration environments: reducing, neutral to alkaline, and oxidizing and acidic. As in NWA 6148 and NWA 10153, the assemblage of alteration mineral species in other nakhlites is also heterogeneous even within the same lava unit. The nakhlite body was altered by the oxidizing acidic fluid after a CO32−-bearing reducing neutral to alkaline fluid. The drastic change of alteration environments may have been caused by an impact event.

^1,2,3Jiaxin Xi,^1,3Yiping Yang,^1,2,3Hongping He,^1,3Haiyang Xian; Shan Li,^1,3Xiaoju Lin,^1,2,3Jianxi Zhu,⁴H. Henry Teng
American Mineralogist 110, 171-180 Link to Article [https://doi.org/10.2138/am-2023-9214]
¹CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²University of Chinese Academy of Sciences, Beijing, China
³CAS Center for Excellence in Deep Earth Science, Guangzhou, China
⁴Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China

We currently do not have a copyright agreement with this publisher and cannot display the abstract here