¹Mingming Zhang, ^1,3Kohei Fukuda, ²Michael J. Tappa, ²William O. Nachlas, ²²Bil Schneider, ⁴Makoto Kimura, ¹Kouki Kitajima, ²Ann M. Bauer, ¹Noriko T. Kita
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.12.056]
¹WiscSIMS, Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA
²Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA
³Graduate School of Science, The University of Osaka, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
⁴National Institute of Polar Research, Meteorite Research Center, Midoricho 10-3, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

Chondrules, ferromagnesium spherules prevalent in undifferentiated extraterrestrial materials, are the main high-temperature products of the protoplanetary disk. Relict minerals within them directly record precursor compositions and thermal histories, offering critical constraints on the long-debated chondrule heating mechanism. We identified pervasive relict refractory anorthites in Al-rich chondrules (bulk Al2O3 ≥10 wt%, ARCs) from pristine carbonaceous chondrites. These anorthites form rims around relict spinel aggregates or intergrow with high-Ca pyroxene/olivine relics, indicating preferential recycling of anorthite-rich inclusions during outer-disk chondrule heating events over more abundant melilite-rich ones. The wide occurrence of relict anorthite, which can be readily melted or dissolved in chondrule melts, suggests these ARCs were most likely formed by one-time crystallization. Thus, their Al-Mg ages of ∼2.0–2.5 Ma after CAIs imply refractory materials were continuously involved over nearly the entire period of chondrule formation. Additionally, we infer that a portion of co-formed iron-poor ferromagnesium chondrules must have similarly escaped completely remelting by subsequent intense heating events in the same reservoirs. These findings suggest that the intense heating events that lead to carbonaceous chondrule formation are localized and infrequent, aligning with mechanisms like bow shocks, lightning discharges, and impact jetting but not the large-scale nebular shocks.

^1,2William F. McDonough
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.12.060]
¹Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Department of Earth Sciences and Research Center for Neutrino Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
²Department of Geology, University of Maryland, College Park, MD 20742, USA
Copyright Elsevier

One in every two atoms in the Earth, Mars, and the Moon is oxygen; it is the third most abundant element in the solar system. The oxygen isotopic compositions of the terrestrial planets are different from those of the Sun and demonstrate that these planets are not direct compositional analogs of the solar photosphere. Likewise, the Sun’s O/Fe, Fe/Mg and Mg/Si values are distinct from those of inner solar system chondrites and terrestrial planets. These four elements (O, Fe, Mg, Si) make up 90% to 94% by mass (and atomic %) of the rocky planets, and their abundances are determined uniquely using geophysical, geochemical, and cosmochemical constraints.

The rocky planets likely grew rapidly (with    10 million years) from large populations of planetesimals, most of which were differentiated, having a core and a mantle, before being accreted. Planetary growth in the early stages of protoplanetary disk evolution was rapid and was only partially recorded by the meteoritic record. The noncarbonaceous meteorites (NC) provide insights into the early history of the inner solar system and are used to construct a framework for how the rocky planets were assembled. NC chondrites have chondrule ages that are two to three million years younger than  (the age of calcium–aluminum inclusions, CAI), documenting that NC chondrites are middle- to late-stage products of solar system evolution.

The composition of the Earth, its current form of mantle convection, and the amount of radiogenic power that drives its engine remain controversial topics. Earth’s dynamics are driven by primordial and radiogenic heat sources. Measurement of the Earth’s geoneutrino flux defines its radiogenic power and restricts its bulk composition. Using the latest data from the KamLAND and Borexino geoneutrino experiments affirms that the Earth has   20 TW of radiogenic power and sets the proportions of refractory lithophile elements in the bulk silicate Earth at   2.7 times that in CI chondrites. The bulk Earth and the bulk Mars are enriched in refractory elements about 1.9 times that of the CI chondrites. Earth is more volatile-depleted and less oxidized than Mars.

¹Eleanor C. McIntosh, ¹James M.D. Day
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.059]
¹Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
Copyright Eslevier

The Apollo 17 high-Ti orange (74220) and Apollo 15 low-Ti green (15426) lunar pyroclastic glasses are some of the most primitive igneous samples from the Moon and are considered critical for understanding the volatile content of the lunar interior. The orange and green glass deposits are petrologically distinct, containing both holohyaline (glassy) and crystallized beads. In this study, edge and center analyses on holohyaline beads representative of the deposits were conducted by laser ablation inductively coupled plasma mass spectrometry to constrain the distribution of moderately volatile elements (MVE: K, Cu, Zn, Cs, Ga, Ge, Rb, Cd, and Pb), and trace element images were produced of the beads in 74220. Bead edges have elevated MVE abundances compared to centers in the larger (107 µm average diameter) low-Ti Apollo 15 green glasses, likely resulting from syn-eruptive processes. Leaching experiments of 15,426 bulk beads support a large fraction of Na, K, Zn, Cd, Cd and Pb on their outer surfaces. The smaller (42 µm average diameter) high-Ti Apollo 17 orange glasses have a greater extent of overlap in MVE contents between bead edges and centers. Orange and green glass bead centers offer approximations of melt MVE abundances, indicating ∼500 µg/g K, ≤20 µg/g Zn, ∼6 µg/g Cu, <4 µg/g Ga and ≤ 1 µg/g Rb and <0.1 µg/g Pb and ≤ 100 µg/g K, ≤1 µg/g Zn, ≤2.5 µg/g Cu, <2 µg/g Ga and ≤ 0.5 µg/g Rb and Pb, respectively. These estimates are as much as ten times lower than bulk bead abundances for these and other MVE within the pyroclastic glass deposits, are depleted compared to terrestrial mid-ocean ridge basalts, and are similar, or lower than, bulk silicate Earth (BSE) concentration estimates. Partial melting estimates for the source of the pyroclastic glass beads indicate similarities with tholeiitic and komatiite lavas on Earth and between ∼10 and 30 % melting of their mantle source, consistent with high mantle potential temperatures at ∼3.5 billion years ago in the Moon. The estimated MVE composition of the orange glass bead mantle source is marginally higher than the green glass mantle source, and both are within or lower than bulk silicate Moon estimates. More shallowly derived mare basalts have been shown to be yet more MVE depleted, indicating that the lunar interior had a heterogeneous distribution of volatile elements, with a deep interior with volatile abundances ∼10 times lower than BSE, volatile-poor upper magma ocean cumulates, and an incompatible volatile-enriched KREEP reservoir.

¹Martin R. Lee,¹Jasper Glazer
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70089]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
Published by arrangement with John Wiley & Sons

Alteration of historic CI1 meteorite falls during their curation demonstrates the susceptibility of smectite-rich carbonaceous chondrites to terrestrial exposure. The discovery of Oued Chebeika 002 in Morocco in June 2024 presents a unique opportunity to document the earliest stages of weathering of a CI1 find. We studied 10–30 mg fragments that had been recovered by September 2024. Grains of quartz and feldspar were implanted into the fragments by wind action whilst on the desert floor. Gypsum is the main product of terrestrial weathering. It encrusts their outer surfaces, in one case covering 5.3% of a fragment, and has filled voids within both fractures and phyllosilicate clasts. Other products of terrestrial weathering are Ca-carbonate grains that have grown within a sand-filled fracture, and rock inhabiting fungi colonizing the surface of a fragment. Chemical weathering was facilitated by water that had been adsorbed by smectite from the humid desert air, and crystallization of gypsum was driven by evaporation from the surfaces of those fragments that were exposed to direct sunlight. The gypsum and Ca-carbonate grew over a period of 3 or 4 months, approximately between June and September 2024, whereas the time scale of fungal colonization can only be constrained to a year or less. The rapid interaction of Oued Chebeika 002 with the Earth’s atmosphere, lithosphere, and biosphere underscores the importance of prompt recovery and careful curation of CI1 and other smectite-rich meteorites.

¹S.James et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70081]
¹Department of Geology, University of Kerala, Thiruvananthapuram, India
²Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

At ~66 Ma, the Cretaceous–Paleogene Boundary (KPB) sections at Anjar and Um Sohryngkew (India) were 14,333 and 16,549 km, respectively, from Chicxulub, making them the farthest distal KPBs. The spatial and temporal proximity of the sites to Deccan volcanism makes them important locations to better understand the impact-volcanism debate. This study integrates petrological, mineralogical, and geochemical techniques to distinguish signatures of the instantaneous Chicxulub impact from those of the prolonged Deccan volcanism (lasting ~10 my). The sites contained two ejecta components: a potential spherule (Um Sohryngkew) and Ir-anomalies. The poorly preserved spherule (~240 μm diameter) exhibited mineral dendrites. At Anjar, two Ir-anomalies are noted: 8.50 ppb (SGA-2; ~3.19 m below Flow IV) and 1.16 ppb (SGA-12). Four Ir-anomalies are noted at Um Sohryngkew: 1.36 ppb (SMU-19; 28.44 m from the oldest layer), 3.17 (SMU-14), 7.00 (SMU-7), and 1.19 ppb (SMU-6). Multiple Ir-anomalies, elevated background-Ir, and glass shards at both sites highlight a greater influence of Deccan volcanism than previously recognized. Deccan magma-based Ir-enrichment is unlikely as such values were not reported in Deccan basalts, but higher Ir-concentrations in sedimentary layers point to indirect contributions from Deccan outgassing. Thus, the findings of the study underscore the complex interplay of Deccan volcanism and Chicxulub impact across the Indian Subcontinent.

¹Eleanor C. McIntosh, ¹James M.D. Day
Geochimics et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.059]
¹Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
Copyright Elsevier

The Apollo 17 high-Ti orange (74220) and Apollo 15 low-Ti green (15426) lunar pyroclastic glasses are some of the most primitive igneous samples from the Moon and are considered critical for understanding the volatile content of the lunar interior. The orange and green glass deposits are petrologically distinct, containing both holohyaline (glassy) and crystallized beads. In this study, edge and center analyses on holohyaline beads representative of the deposits were conducted by laser ablation inductively coupled plasma mass spectrometry to constrain the distribution of moderately volatile elements (MVE: K, Cu, Zn, Cs, Ga, Ge, Rb, Cd, and Pb), and trace element images were produced of the beads in 74220. Bead edges have elevated MVE abundances compared to centers in the larger (107 µm average diameter) low-Ti Apollo 15 green glasses, likely resulting from syn-eruptive processes. Leaching experiments of 15,426 bulk beads support a large fraction of Na, K, Zn, Cd, Cd and Pb on their outer surfaces. The smaller (42 µm average diameter) high-Ti Apollo 17 orange glasses have a greater extent of overlap in MVE contents between bead edges and centers. Orange and green glass bead centers offer approximations of melt MVE abundances, indicating ∼500 µg/g K, ≤20 µg/g Zn, ∼6 µg/g Cu, <4 µg/g Ga and ≤ 1 µg/g Rb and <0.1 µg/g Pb and ≤ 100 µg/g K, ≤1 µg/g Zn, ≤2.5 µg/g Cu, <2 µg/g Ga and ≤ 0.5 µg/g Rb and Pb, respectively. These estimates are as much as ten times lower than bulk bead abundances for these and other MVE within the pyroclastic glass deposits, are depleted compared to terrestrial mid-ocean ridge basalts, and are similar, or lower than, bulk silicate Earth (BSE) concentration estimates. Partial melting estimates for the source of the pyroclastic glass beads indicate similarities with tholeiitic and komatiite lavas on Earth and between ∼10 and 30 % melting of their mantle source, consistent with high mantle potential temperatures at ∼3.5 billion years ago in the Moon. The estimated MVE composition of the orange glass bead mantle source is marginally higher than the green glass mantle source, and both are within or lower than bulk silicate Moon estimates. More shallowly derived mare basalts have been shown to be yet more MVE depleted, indicating that the lunar interior had a heterogeneous distribution of volatile elements, with a deep interior with volatile abundances ∼10 times lower than BSE, volatile-poor upper magma ocean cumulates, and an incompatible volatile-enriched KREEP reservoir.

^1,2Marine Paquet, ¹James M.D. Day, ³Arya Udry
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.019]
¹Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA
²Université de Lorraine, CNRS, CRPG F-54000 Nancy, France
³Department of Geoscience, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, NV 89154, USA
Copyright Elsevier

The nakhlite and chassignite meteorites are the only confirmed group of rocks derived from a single volcanic system on Mars, offering a unique opportunity to investigate the composition of the martian mantle and magmatic differentiation mechanisms. Nakhlites and chassignites are thought to result from low-degree partial melting of a hydrated and metasomatized depleted mantle lithosphere, unlike shergottites that predominantly sample deeper mantle reservoirs. This study presents the first comprehensive dataset on highly siderophile element (HSE: Au, Re, Pd, Rh, Pt, Ru, Ir, Os) abundances in sulfide assemblages from twelve nakhlites and two chassignites, together with siderophile (Ni, Co, W) and chalcophile (Cu, Se, Zn, Pb) element abundance data. Sulfides in chassignites exhibit relatively high total HSE abundances at ∼ 5 × carbonaceous (CI) chondrite abundances, with patterns that are generally flat, apart from notable enrichments in Pt and/or Ru. Conversely, nakhlite sulfides display more fractionated HSE patterns with total HSE abundances ∼ 1.6 × CI, characterized by lower overall abundances and enrichment in Re, Pt and Pd relative to Ru, Ir and Os. These results confirm that sulfides are the principal reservoirs of HSE in chassignites and nakhlites. Fractionation modeling suggests that the nakhlite compositions can be reproduced following up to 15 % fractional crystallization through the removal of an olivine (+Cr-spinel)-dominated cumulate, while chassignites experienced between 20 to 30 % of fractionation. The preservation of magmatic signatures in sulfide HSE compositions allows for an in-depth reconstruction of the evolution of the nakhlite-chassignite parental melt composition.

¹Martin R. Lee, ¹Sammy Griffin, ^2,2Ross Findlay, ³Xuchao Zhao, ³Ian A. Franchi
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.051]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
²Department of Earth Sciences, University of Cambridge, Downing St., Cambridge CB2 3EQ, UK
³School of Physical Sciences, Open University, Milton Keynes MK7 6AA, UK
Copyright Elsevier

The CM2 meteorites Grove Mountains (GRV) 021536, Murchison, and Shidian, contain anhydrous lithic clasts that have been interpreted as fragments of a planetesimal linked to CM or CV group carbonaceous chondrites. Here we describe 57 lithic clasts in Cold Bokkeveld (CM2) that are strikingly similar to those in the other three CMs in their petrography, mineralogy, and chemical and isotopic compositions. The Cold Bokkeveld clasts are dominated by equilibrated olivine, with subordinate plagioclase feldspar (andesine), clinopyroxene (diopside), nepheline, a spinel-group oxide (ferrian chromite), pentlandite, pyrrhotite, troilite and merrillite. Their bulk chemical composition is chondritic, and olivine oxygen isotope values span a wide range, from δ18O 3.6 ‰ Δ17O −3.9 ‰ to δ18O 20.3 ‰ Δ17O 1.1 ‰. Two clusters of clasts can potentially be distinguished from the chemical composition of their olivine: Fa38 and Fa41. The Fa38 cluster includes most of Cold Bokkeveld’s clasts and is close in chemical composition to those described from GRV 021526 and Murchison. The Fa41 cluster is represented by the largest Cold Bokkeveld clast, and its olivine is compositionally comparable to that in Shidian. Anhydrous lithic clasts that occur in all four of the CM meteorites are likely to have been derived from a large planetesimal with CM and CY affinities that had undergone thermal metamorphism and metasomatism. The CV3 breccias Mokoia and Yamato 86009 contain anhydrous lithic clasts that are close in mineralogy and oxygen isotopic composition to those in the four CMs and so are likely to have been sourced from the same carbonaceous planetesimal or one with a similar geological history. The oxygen isotopic compositions of olivine in clasts from GRV 021536, Murchison, Shidian, Cold Bokkeveld, Mokoia and Yamato 86009 plot on a shared trendline in 3-oxygen isotope space that connects the CV-CK-CO, CM, and CY fields thus suggesting genetic or evolutionary links between the five carbonaceous chondrite groups. The occurrence of these distinctive clasts in four CM2 meteorites could indicate that their parent body was the same rubble pile asteroid that had been built from aqueously altered and thermally metamorphosed lithologies.

¹Bennett J.K. Wilson, ²Kazuhide Nagashima, ^3,4Thomas J. Barrett, ⁵Veronica E. Di Cecco, ^5,6Kimberly T. Tait, ¹Michael G. Daly
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.12.046]
¹Center for Research in Earth and Space Science, York University, Toronto, ON, Canada
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, 1680 East-West Road, POST602, Honolulu HI96822, USA
³Department of Earth and Environmental Sciences, The University of Manchester, UK
⁴Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, TX, USA
⁵Department of Natural History, Center for Applied Planetary Mineralogy, Royal Ontario Museum, Toronto, ON, Canada
⁶Department of Earth Science, University of Toronto, ON, Canada
Copyright Elsevier

The Tarda meteorite is a recently recovered C2-ungrouped carbonaceous chondrite that preserves evidence of early Solar System aqueous alteration. Tarda was found to share reflectance spectra with P-type asteroids, possibly enabling these elusive asteroids to be studied in the laboratory for the first time. Furthermore, Tarda has been shown to share many petrological and isotopic affinities with Tagish Lake – a pristine C2-ungrouped chondrite that is widely considered to source a D-type asteroid. Thus Tarda, Tagish Lake, and their respective spectral classes are probably genetically related, and potentially source a shared parent body. Despite their similarities, however, Tagish Lake hosts different lithologies and carbonate species than Tarda, suggesting distinct aqueous alteration histories between the two meteorites. Here, we present in-situ oxygen, carbon, and 53Mn–53Cr isotopic analyses of dolomite and magnetite in Tarda using Secondary Ion Mass Spectrometry to (i) investigate the conditions associated with aqueous alteration on the early Tarda parent body, and to (ii) compare our findings with Tagish Lake to assess heterogeneous aqueous alteration of their unique and likely shared parent body. For dolomite, we found that δ13C ranged from 55.8 ‰ to 72.9 ‰, while δ18O ranged from 23.3 ‰ to 28.8 ‰ with an average Δ17O of 0.1 ± 1.6. Dolomite additionally contained widespread 53Cr excesses that, if interpreted to have chronological significance, corresponds to a live [(53Mn/55Mn)0] value of (
. For magnetite, the δ18O values ranged from −5.5 ‰ to 5.8 ‰ with an average Δ17O of 2.4 ‰ ± 1.7. Oxygen isotope thermometry of a co-precipitating dolomite–magnetite pair indicates alteration temperatures of
°C. Compared to carbonates in Tagish Lake, dolomite in Tarda exhibits systematically lower δ17O, δ18O, and Δ17O signatures, but similar δ13C signatures. Temporally, the carbonates in both meteorites have identical ages within uncertainty. We conclude that Tarda has experienced greater aqueous alteration than Tagish Lake, likely due to increased water–rock interaction and/or higher temperatures.

¹L.J. Riches, ^1,2M.D. Suttle, ¹I.A. Franchi, ¹X. Zhao, ^1,2M.M. Grady
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.035]
¹School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom
²Planetary Materials Group, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
Copyright Elsevier

Analysis of carbonate minerals in ungrouped carbonaceous chondrites offer valuable insights into the geological activity on a diverse range of early-formed, hydrated planetesimals in the outer Solar System. Essebi is a C2-ung chondrite, which originated from a water-rich asteroid with close affinities to the CM chondrites group. We performed a detailed geochemical, petrographic and isotopic study of Essebi. Modal mineralogy demonstrates that Essebi is dominated by a poorly crystalline, fine-grained phyllosilicate matrix (mostly a mix of saponite and serpentine ∼63 vol%) with a modest quantity of anhydrous silicates (20 vol%) and accessory magnetite (7.5 vol%), Fe-sulphides (5.5 vol%) and carbonates (2 vol%). Its bulk O-isotope composition (2.71 ‰ δ17O (± 0.018 1σ), 8.11 ‰ δ18O (± 0.002 1σ) and −1.53 ‰ Δ17O (± 0.017 1σ) and 2.56 ‰ δ17O (± 0.040 1σ), 7.65 ‰ δ18O (± 0.009 1σ) and −1.42 ‰ Δ17O (± 0.039 1σ)) places Essebi as part of the “CM field”, although overlapping with the “CR field”. Petrographic observations reveal multiple generations of carbonate that formed both before and after brecciation, exhibiting distinct characteristics that differ from the carbonates found in established groups (CMs). Essebi’s carbonate generations have distinct morphologies and C- and O- isotope compositions and, based on these data, are interpreted as two main generations and a series of other localised carbonate expressions.
The first generation (GA) carbonates formed prior to phyllosilicate growth, and have inferred maximum formation temperatures of +45 °C. They formed under high water-to-rock (W/R) ratios. The second generation (GB) carbonates show lower W/R ratios and at higher, although unquantified temperatures. They formed near the end of the alteration sequence from a residual fluid containing abundant dissolved cations. In addition to the two main generations, we identified a third population of vein carbonates (GC) that partially infilled fractures generated by brecciation. We also identified dolomite (GD) grains found exclusively within an xenolithic clast. This clast displays a more advanced stage of alteration (C1-ung) and shows evidence of fluid leaching after being embedded, resulting in the formation of a localized ring of calcites, referred to as GE, that remain distinct from all other carbonates in this sample.
Despite textural differences, the isotopic trends observed in these Essebi carbonates closely resemble the sequence described by T1 and T2 calcites in CM chondrites, suggesting that multiple distinct episodes of carbonate precipitation, aqueous alteration along a prograde metasomatic sequence, and isotopic evolution from 16O-poor to 16O-rich trajectories were common across several water-rich planetesimals that formed in the outer Solar System.