^1,2,3,4Ke Zhu 朱柯, ⁵Peng Ni, ⁶Qi Chen, ⁷Mahesh Anand, ²Meng-Hua Zhu, ⁴Tim Elliott
Earth and Planetary Science Letters 683, 119974 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2026.119974]
¹State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia
⁴Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, United Kingdom
⁵Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095, USA
⁶Department of Earth Science & Environmental Change, University of Illinois at Urbana Champaign, Urbana, IL, USA
⁷School of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom
Copyright Elsevier

Although the Moon is thought to have formed through a giant impact between proto-Earth and a Mars-sized body, the processes responsible for the chemical and mass-dependent isotopic differences between Earth and Moon remain debated. We report high-precision mass-dependent Ni isotope data for 19 Apollo samples, including one dunite (72415), fifteen low-Ti basalts, and three high-Ti basalts, analyzed by double-spike technique using a multi-collector plasma-sourced mass spectrometer. The dunite 72415 shows an extremely high δ60/58Ni value of +1.80 ± 0.01‰, which we attribute to kinetic isotope fractionation from Ni diffusion during re-equilibration between olivine and a later melt. Diffusion modeling of Ni–Fe–Mg systematics reproduces the observed heavy Ni enrichment. In contrast, low-Ti basalts display a mean δ60/58Ni of 0.23 ± 0.20‰ (2SD), unaffected by cosmic-ray exposure, while high-Ti basalts are slightly isotopically lighter (0.06 ± 0.22‰, 2SD). Petrological modeling using pMELTS with recently constrained silicate mineral-melt fractionation factors suggests limited Ni isotope fractionation (<0.05‰) during lunar magma ocean crystallization and partial melting, yielding an estimated bulk silicate Moon (BSM) δ60/58Ni = 0.18 ± 0.20‰ (2SD). This overlaps with the bulk silicate Earth (BSE: 0.11 ± 0.07‰), indicating that Ni depletion in the lunar mantle, by a factor of ∼4 relative to Earth, can be caused by core formation (that does not fractionate Ni isotopes). However, our modelling shows evaporative loss of Ni can elevate δ60/58Ni value of < 0.23‰, which remains consistent with those of BSM within uncertainty. Hence, the mechanism of Ni evaporation cannot be ruled out.

¹Toni Schulz,¹Christian Koeberl,^1,2Olivier Heldwein,³Bo-Magnus Elfers,⁴Jonas Tusch,⁵Stefan T. M. Peters,⁶Andreas Pack,⁴Carsten Münker
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70124]
¹Department of Lithospheric Research, University of Vienna, Vienna, Austria
²Institute of Social Ecology, University of Natural Resources and Life Sciences, Vienna, Austria
³Technische Universität Hamburg, Zentrallabor Chemische Analytik, Hamburg, Germany
⁴Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany
⁵Zentrum für Biodiversitätsmonitoring, Leibniz-Institut zur Analyse des Biodiversitätswandels, Hamburg, Germany
⁵Geowissenschaftliches Zentrum, Georg-August-Universität Göttingen, Göttingen, Germany
Published by arrangement with John Wiley & Sons

Archean impact spherule layers represent exceptional archives of extraterrestrial (ET) material, containing large amounts of ET highly siderophile elements (HSE) that dominate the bulk content of these elements. This enrichment makes them prime targets for testing additional impact tracers, such as ε182W and triple oxygen isotopes. We investigated samples from the Paleoarchean BARB5 drill core (Barberton Mountain Land, South Africa), which preserves four spherule layers with chondritic HSE contents and 187Os/188Os signatures. Tungsten isotope data from bulk spherule layer samples yield ε182W values indistinguishable from the bulk silicate Earth, most likely reflecting the limited sensitivity of the ε182W composition to detect meteoritic admixture. If present, such a component must lie within analytical uncertainties, limiting contributions to ≤6% for a chondritic endmember or ≤3% for an iron-meteorite endmember, unless a larger signal was erased by postimpact hydrothermal overprint. In addition, bulk triple oxygen data fall within Archean shale fields and do not show resolvable ET signatures, consistent with a chondritic contribution of at most ~5% given analytical uncertainties; elevated 18O values most likely reflect seawater alteration of glass spherules. Thus, despite clear HSE–Os isotope evidence for admixture of ET components, ε182W and oxygen isotopes yield no such information. This can be explained by plume condensation models predicting temporally separated fallout of refractory and volatile element carriers. To test this, we separated spherules, matrix, and mixed fractions from one of the four BARB5 beds. While the matrix hosts the highest HSE contents and least radiogenic 187Os/188Os, spherules have the lowest HSE contents and slightly more radiogenic 187Os/188Os signatures, with mixed fractions being intermediate. Together with highly siderophile interelement trends, these results most likely highlight stepwise condensation followed by early syn-depositional to diagenetic alteration, establishing Archean spherule beds as unique probes of early plume dynamics and impact processes.

¹Chi Ma,²Oliver Tschauner,³John G. Spray,⁴Zhongxu Pan
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70129]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²Department of Geoscience, University of Nevada, Las Vegas, Nevada, USA
³Planetary and Space Science Centre, University of New Brunswick, Fredericton, New Brunswick, Canada
⁴School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China
Published by arrangement with John Wiley & Sons

We report a previously unknown aluminosilicate mineral, (Si0.91□0.09)Σ1.00(Al1.46□0.54)Σ2.00O4 with a vacancy-stabilized spinel-type structure (henceforth “SiAl-spinel”). This novel aluminosilicate occurs with coesite, stishovite, and majoritic garnet in a shock melt vein in metaquartzite from the outer collar of the Vredefort Dome, the eroded central uplift of the Vredefort impact structure of South Africa. Formation conditions for this new high-pressure, high-temperature phase are around 10 GPa and 1400°C, upon release from peak shock conditions. Based on its composition and formation conditions, this new high-pressure, high-temperature phase is predicted to be a common occurrence in terrestrial impactites and in subducted slabs.

^1,2Lidia Pittarello,³Valeria De Santis,³Laura Carone,⁴Giovanni Pratesi,⁵Mauro Gemmi,⁵Paola Parlanti,⁶Andreas Steiger-Thirsfeld,⁷Alessandro Di Michele,³Gabriele Giuli
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70134]
¹Naturhistorisches Museum, Mineralogisch-Petrographische Abteilung, Vienna, Austria
²Department of Lithospheric Research, University of Vienna, Vienna, Austria
³Geology Divison, School of Science and Technology, University of Camerino, Camerino, Italy
⁴Department of Earth Sciences, University of Firenze, Firenze, Italy
⁵Electron Crystallography, Istituto Italiano di Tecnologia, Pontedera, Italy
⁶Technische Universit€at Wien, University Service Center for Transmission Electron Microscopy, Vienna, Austria
⁷Department of Physics and Geology, University of Perugia, Perugia, Italy
Published by arrangement with John Wiley & Sons

The occurrence of ringwoodite in shocked L6 ordinary chondrites has been frequently reported, mostly within shock veins. Only recently, ringwoodite has also been found in a fragment from the Alfianello meteorite, occurring as rim or core of olivine clasts in impact melt pockets, in lamellae crosscutting olivine grains in the host rock, and in fine-grained aggregates in association with wadsleyite. In all cases, ringwoodite shows a higher Fe/Mg ratio than the original olivine, whereas wadsleyite shows a lower Fe/Mg ratio than the original olivine. Detailed TEM studies of the occurrence of both high-pressure polymorphs allow the identification of the most likely formation process, explaining the coexistence of these polymorphs. The lack of any crystallographic relationships but the complementary Fe/Mg ratios supports formation of the assemblage through fractional crystallization from impact melt under high (shock) pressure conditions. However, the other occurrences of ringwoodite reported in the same sample, traditionally interpreted as resulting from solid-state transformation, emphasize the heterogeneity of distribution of shock effects and shock-induced processes recorded in a single meteorite.

^1,2,3M. R. Boyd,^1,2M. J. Genge,⁴A. G. Tomkins
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70123]
¹Department of Earth Science and Engineering, Imperial College London, London, UK
²Natural History Museum, London, UK
³Grantham Institute – Climate Change and the Environment, Imperial College London, London, UK
⁴School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
Published by arrangement with John Wiley & Sons

Natural microspherules are formed by high-temperature processes and are present throughout the geologic record to the present day. We report the discovery of large numbers of microspherules recovered from a rock pavement in the Pilbara region, Western Australia. Textures range from glassy to coarse-grained, with many particles containing crystallites, vesicles, and relict grains. Compositions are non-chondritic and are either dominated by silicates or Fe-Ti-bearing oxides. Spherule and relict grain compositions show strong affinities to the mineralogy of the underlying rock, a Paleoarchean granite gneiss. Bulk compositions suggest formation by a localized melting process with precursors dominated by individual pre-existing minerals, with minimal mixing. Numerical modeling of the formation of spherules suggests formation by rapid quenching, possibly from melt droplets. Modeled cooling times are consistent with compositions that indicate limited evaporation. The compositions and textures of these spherules are not compatible with either microtektites formed by meteor impact or micrometeorites formed by the atmospheric entry of cosmic dust and are instead interpreted to have formed via lightning strikes. Spherules generated by lightning strikes may be present in the geologic record and thus could be used as a paleoclimate proxy where other signatures, such as main mass fulgurites, have not survived.

¹Neeraj Srivastava et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70121]
PRSS, PSDN, Physical Research Laboratory, Ahmedabad, India
Published by arrangement with John Wiley & Sons

Estimating mineral abundance in meteorites provides crucial information about the early solar system and planetary formation processes. This study presents a new empirical approach for the estimation of modal abundance of olivine (Ol), high-calcium pyroxene (HCP), and low-calcium pyroxene (LCP) using band area ratio (BAR), a spectral parameter derived using reflectance spectroscopy. Using spectral data of 22 mineral mixtures acquired from the RELAB spectral library, the BAR values were initially calculated. These BAR values were then plotted against Ol% and HCP%, and based on the trends observed, a set of equations was formulated to get the initial estimate of mineral abundances. To apply these to actual samples, an error reduction framework has been developed that involves determination of a class-specific correction factor (CF) for H, L, and LL types of ordinary chondrites (OCs) to account for the presence of other minerals, metals, and impurities. The CF is a quantitative adjustment that is subtracted from the initial estimates to align calculations with the actual values. After application of the CF, the 1σ uncertainties associated with the abundance estimates were found to be ±1.85% for Ol, ±0.91% for HCP, and ±1.63% for LCP. The study demonstrates the estimation of the mineral abundances of seven OCs, using spectral analysis conducted at the Planetary Remote Sensing Laboratory (PRSL), Physical Research Laboratory (PRL). The proposed approach is robust even for bulk samples analyzed under different viewing geometries and provides a rapid, nondestructive alternative to traditional techniques for mineral abundance estimation in meteorites, planetary samples, and analogs.

¹Martyna Jakubowska,¹Jolanta Gałązka-Friedman,²Marek Woźniak,³Krzysztof Szopa,⁴Katarzyna Brzózka,⁵Barbora Pospíšilová,⁶Agnieszka Grabias
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70122]
¹Faculty of Physics, Warsaw University of Technology, Warsaw, Poland
²Faculty of Biology, University of Warsaw, Warsaw, Poland
³Faculty of Natural Sciences, University of Silesia, Sosnowiec, Poland
⁴Faculty of Mechanical Engineering, Casimir Pulaski Radom University, Radom, Poland
⁵Faculty of Science, Palack´y University Olomouc, Olomouc, Czech Republic
⁶Łukasiewicz Research Network—Institute of Microelectronics and Photonics, Warsaw, Poland
Published by arrangement with John Wiley & Sons

The paper presents a modified version of the 4M method, which is the latest method of classifying ordinary chondrites, based on their Mössbauer spectra measured at room temperature. The proposed changes, including the introduction of a new criterion for assessing which group (H, L, or LL) the meteorite being tested belong to, are expected to improve the plausibility of classification by the 4M method. The modification makes use of the Bayesian analysis and the maximum a posteriori probability. This modified version of the 4M method was tested by attempting to classify 20 samples of ordinary chondrites: 8 of type H, 7 of type L, and 5 of type LL. The results were compared with those obtained by the classical method of ordinary chondrite classification. The vast majority of classification tests performed using the new version of the 4M method were consistent with the classical method for group assignment, except for one L-type sample that was classified differently. It was also shown that the introduction of a new criterion resulted in a significantly better agreement with the established classification than in the case of the level of similarity criterion used in the previous version of the 4M method.

¹N. Randazzo,¹R. W. Hilts,²R. M. Whittal,²B. Reiz,¹V. Olan-Rubio,¹C. D. K. Herd,³I. H. Krouse
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701271]
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
²Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
³School of Science and Technology, Georgia Gwinnett College, Lawrenceville, Georgia, USA
Published by arrangement with John Wiley & Sons

Solvent extraction is a cornerstone of meteoritic organic and inorganic chemistry,yet the assumption that common solvents act as chemically inert media is becomingincreasingly untenable. This study reports that low-molecular-weight alcohols, particularlymethanol and ethanol, are “non-innocent” solvents when used to extract soluble sulfurspecies from carbonaceous chondrites. Laboratory extractions of Tagish Lake and Allendesamples demonstrate that these alcohols readily esterify meteoritic sulfate, producing largequantities of methyl and ethyl sulfate artifacts. Using isotopically labeled methanol(CD 3 OH) in 1:1 water mixtures, it is shown that >99% of the methyl sulfate signalpreviously attributed to indigenous methyl sulfate is actually solvent-derived. Correctedabundances fall from hundreds of nmol g1 reported in earlier studies to < 0.2 nmol g1 ,revealing that intrinsic methyl sulfate is only a trace constituent. Control experimentsindicate that esterification requires both acidic conditions and solid meteoritic matrices,implicating Fe-bearing phyllosilicates and oxides as heterogeneous catalysts. Additionalexperiments confirm that sulfate ester formation does not occur in solution-only systems,underscoring the catalytic role of mineral–solvent interfaces. These findings not onlynecessitate a downward revision of reported organosulfur inventories in carbonaceouschondrites but also highlight a broader issue: solvent-driven reactions can significantly alterthe apparent chemical record of extraterrestrial materials. It is recommended thatisotope-labeled solvents and mixed-solvent systems are employed as standard practice infuture extractions, both to minimize artifact generation and to maximize analyte coverageacross polarity ranges. Recognizing and mitigating solvent reactivity is essential for ensuringthat laboratory analyses faithfully represent intrinsic extraterrestrial chemistry rather thanexperimental artifacts.

^1,2A.P. Singh, ³S.S. Pillai, ¹K.K. Marhas, ⁴K.V.N.G. Vikram, ⁴S. Bhattacharya
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117045]
¹Physical Research Laboratory, Ahmedabad, Gujarat, India
²Department of Earth Science, Gujarat University, Ahmedabad, Gujarat, India
³University of Kerala, Thiruvananthapuram, Kerala, India
⁴Space Applications Centre, Ahmedabad, Gujarat, India
Copyright Elsevier

This study investigates the mid-infrared spectral correlation between four Carbonaceous Vigarano (CV) chondrites (Allende, Grosnaja, Efremovka and Leoville) and ten asteroids of Xk, L, & Ld types (Bus- Binzel taxonomy). It leverages the mid-infrared region of the electromagnetic spectrum, which is characterised by prominent peaks indicative of crystalline bond vibrations of silicates and ionic oxides. A novel statistical methodology, integrating four distinct similarity assessment techniques (normalised local change method, covariance, Euclidean distance, and cosine similarity), was employed to determine the spectral similarity coefficient (Z) between the CV chondrites and the chosen asteroids. The highest similarity is observed between the asteroids of L type, i.e., Cantillo et al. (2023) (Cantillo et al., 2023) Victoria, (1284) Kassandra, and (1702) Latvia and the CV chondrites studied here, followed by the Xk type (114) Kassandra. The Z value between Ld asteroids (234) Barbara, (269) Justitia and CVs exhibit low similarities. This study establishes a framework for the statistical comparison of mid-infrared spectra of meteorites and asteroids by accounting for compositional variability within CV chondrites, thereby providing a basis for more detailed investigations into the parent-body association of these meteorites.

^1,2Mark Nestmeyer, ^1,3Alex J. McCoy-West
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.03.022]
¹IsoTropics Geochemistry Laboratory, Earth and Environmental Science, James Cook University, Townsville, QLD 4811, Australia
²CSIRO Mineral Resources, Kensington, WA 6151, Australia
³Economic Geology Research Centre, James Cook University, Townsville, QLD 4811, Australia
Copyright Elsevier

The application of rare Earth element stable isotope compositions has become of increasing interest in geochemistry. Recently, studies have begun exploring variations in the stable 146Nd/144Nd isotope ratio in geological samples, with limited isotope fractionation observed in igneous rocks but significantly larger fractionations seen in low temperature systems. Experimental and theoretical studies on the equilibrium isotope fractionation of Nd are widely missing which can support understanding the fractionation of Nd isotopes among Earth’s major reservoirs. Here, we have modelled the isotope fractionation factors for 15 common rock forming and accessory minerals to help understand equilibrium stable isotope fractionation during medium to high temperature processes.
We estimate that mantle melting will produce minimal isotope fractionation while the residual peridotite ought to retain heavier Nd isotopes which could explain a potentially superchondritic composition of the depleted mantle. This can be predicted because in mantle minerals with Mg sites (e.g. olivine, orthopyroxene) substitution of isotopically heavier Nd is preferred compared to minerals with Ca sites (e.g. clinopyroxene), with the latter being the major contributor to basaltic melts. The Earth’s outer core (i.e. sulfide matte) is a potential host of lighter Nd isotopes which we demonstrate favours sulfides over silicates. However, the low partition coefficients of rare Earth elements into the core leads to a composition of the bulk silicate Earth that is indistinguishable from chondrites. A better understanding of the δ146/144Nd composition of the mantle is warranted to elucidate the isotope fractionation of Nd between Earth’s major geochemical reservoirs.
As Nd condenses from the solar nebular gas into primitive material, the mass-independent nuclear field shift effect dominates equilibrium isotope fractionation and produces significant fractionation in δ146/144Nd even at high temperatures (>1000 °C) with the condensed material enriched in lighter Nd isotopes. However, the isotopic compositions reported for refractory inclusions (–1.86 to 2.20 ‰; Hu et al. (2021)) cannot be solely explained by equilibrium isotope fractionation and other mechanisms are required