Rei KANEMARU¹ et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70045]
¹Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
Published by arrangement with John Wiley & Sons

Silica polymorphs in meteorites provide critical constraints on crystallization processes associated with thermal activity in the early solar system. A detailed investigation of silica polymorphs in eucrites (the largest group of achondrites) using cathodoluminescence imaging and laser-Raman spectroscopy revealed significant variations in the relative abundance of silica polymorphs. Based on these variations, the eucrites were divided into four “Si-groups” according to their dominant silica phase: Si-0 (cristobalite-dominant eucrites), Si-I (quartz-dominant eucrites), Si-II (quartz and tridymite-dominant eucrites), and Si-III (tridymite-dominant eucrites). In studied eucrites, tridymite and cristobalite form lathy euhedral shapes, while quartz is anhedral, coexistent with opaques and phosphates, suggesting that silica polymorphs were crystallized from different stages and formation processes. We propose a new model that explains the formation pathways of silica minerals in eucrites and accounts for the distinct formation histories represented by each Si-group: tridymite crystallizes from alkali-rich immiscible melts (starting at ≥ ~1060°C), cristobalite crystallizes from quenched melts (~1060°C), and quartz crystallizes from extremely differentiated melts and/or by solid-state transformation from tridymite and cristobalite through interactions with sulfur-rich vapor below ~1025°C. This model explains the occurrences of silica polymorphs in eucrites without requiring secondary heating or shock processes.

Megan Broussard^a, Mason Neuman^a, Piers Koefoed^a, Frédéric Moynier^b, Nicole X. Nie^c, Richard V. Morris^d, Bradley L. Jolliff^a, Kun Wang^a

Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.09.004]
^aDepartment of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
^bUniversité Paris Cité, Institut de Physique du Globe de Paris, CNRS, UMR 7154, F-75005 Paris, France
^cDepartment of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
^dAstromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX 77058, USA
Copyright Elsevier

As a part of the Apollo Next Generation Sample Analysis Program, we report the Cu and Zn isotopes in the Apollo 17 regolith core, double-drive tube 73001/2. The intervals in the upper core, which sampled the regolith closest to the lunar surface, are enriched in heavy Cu and Zn isotopes compared to the deeper intervals. The top 2 cm have a δ⁶⁵Cu value of 2.85 ± 0.01 ‰ and a δ⁶⁶Zn value of 5.54 ± 0.02 ‰. The intervals become lighter in isotopic composition to a depth of 8 cm. Below this depth, the average δ⁶⁵Cu is 1.02 ± 0.08 ‰, while the average δ⁶⁶Zn is 2.27 ± 0.24 ‰. We find strong correlations between the isotopic fractionations of Cu and Zn and the maturity index I_S/FeO. These correlations in the core result from a binary mixing between highly space-weathered soil at the lunar surface and deeper, shielded soil, with isotopic fractionation occurring at the surface due to space weathering and soil mixing occurring due to impact gardening. Using the K, Fe, Cu, and Zn isotopes measured in 73001/2, we find a strong correlation between the degree of isotope fractionation and volatility. We model the isotopic fractionation of K, Fe, Cu, and Zn by space weathering in lunar soils using mass balance equations between the lunar atmosphere and lunar soil and find agreement with the fractionation observed in 73001/2. Using the fractionation observed in 73001/2, we present a new exposure age model using Cu isotope fractionation in lunar soils.

Rachel S. KIRBY^1,2,3, Penelope L. KING¹, and Andrew G. TOMKINS²
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70040]
¹Sesearch School of Earth Sciences, The Australian National University, Acton, Australian Capital Territory, Australia
²School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
³Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

It has been proposed that IIE iron meteorites formed through impact processes on a parent body that was composed of either the H chondrites or a much-debated fourth ordinary chondrite group, the HH chondrites. To resolve this debate, we have compiled a large dataset for the ordinary chondrites, low-fayalite ungrouped chondrites, and IIE irons, and undertaken a statistical analysis to determine if: (1) the current classification of ordinary chondrite groups is statistically appropriate; and (2) the IIE irons are related to H chondrites or if they represent a distinct group that formed on a “HH” chondrite parent body. We demonstrate that the current classification system based on petrography and olivine and orthopyroxene chemistry is appropriate for the H, L, and LL chondrites. We define a fourth “F chondrite” group consisting of eight, previously ungrouped, very low-Fa Type 3 and 4 chondrites. Statistical analysis of Δ¹⁷O data alone cannot distinguish between the H chondrites and IIE irons, nor between the L and LL chondrites. Furthermore, statistical analyses are unable to distinguish H chondrites from IIE irons in all measures (mineral chemistry, chondrule size, bulk Δ¹⁷O, Ge and Mo isotopic compositions, and bulk siderophile element abundances in metal); there is no evidence for a “HH” chondrite group. These results are consistent with formation of IIE iron meteorites through impact melting and near-surface metal segregation on the H chondrite parent body. This genetic link between H chondrites and IIE irons allows us to understand the geochemical and petrological changes that occurred during planetary formation and evolution.

M. D. SUTTLE^1,2, R. FINDLAY^1,3, I. A. FRANCHI¹, C. BIAGIONI^2,4, X. ZHAO¹,  F. A. J. ABERNETHY¹, L. RICHES¹, and L. FOLCO² 
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70043]
¹School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK
²Dipartimento di Scienze della Terra, Universit`a di Pisa, Pisa, Italy
<sup>3</sup>Department of Earth Sciences, University of Cambridge, Cambridge, UK
<sup>4</sup>CISUP, Centro per l’Integrazione della Strumentazione dell’Universit`a di Pisa, Pisa, Italy
Published by arrangement with John Wiley & Sons

We report the first oxygen isotope measurements of tochilinite (δ¹⁷O: 11.0 ± 2.1‰, δ¹⁸O: 23.5 ± 4.0‰ and Δ¹⁷O: −1.1 ± 1.2‰) in a CM chondrite (Winchcombe, lithology C [CM2.2/2.3]). We analyzed type-I tochilinite-cronstedtite intergrowths (TCIs)—formed by pseudomorphic replacement of kamacite. Alongside T1 and T2 calcite and magnetite, these secondary phases define a linear trendline in δ¹⁷O-δ¹⁸O isotope space with a slope of 0.50, slightly shallower than the mass-dependent slope (0.52). This demonstrates that, in addition to dominant mass-dependent fractionation (controlled by mineral-specific and temperature-dependent equilibrium processes), mass-independent mixing between ¹⁶O-rich anhydrous silicates, and ¹⁶O-poor water influenced the evolving Δ¹⁷O composition of alteration fluids. Petrographic evidence shows tochilinite and T1 calcite formed early and are closely associated in the alteration sequence. Assuming isotopic equilibrium between these phases, we estimate formation temperatures of approximately 135°C and a δ¹⁸O_water value of 28‰. These findings align with previous hydrothermal synthesis experiments and underscore the value of multi-phase isotopic measurements for reconstructing the fluid history of chondritic parent bodies.

Zhi-Ming CHEN^1,2,3, Le ZHANG^1,3, Cheng-Yuan WANG^1,3, Ya-Nan YANG¹, Peng-Li HE¹, Hai-Yang XIAN^1,3,4, Xiao-Ping XIA⁵, Jian-Xi ZHU^1,3,4, and Yi-Gang XU^1,3
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70042]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²University of Chinese Academy of Sciences, Beijing, China
³Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,
Guangzhou, China
⁴Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese
Academy of Sciences, Guangzhou, China
⁵College of Resources and Environment, Yangtze University, Wuhan, China
Published by arrangement with John Wiley & Sons

Numerous studies of basalt clasts in regolith samples returned by the Chang’E-5 (CE-5) mission have provided constraints on the timing and nature of the youngest magmatism on the Moon. However, there have been far fewer studies of breccias, one of the main constituents of regolith. Here, we present a comprehensive investigation of the mineralogy, petrology, and U-Pb geochronology of two CE-5 regolith breccia samples, which are composed of lithic clasts, agglutinates, glass particles, and mineral fragments. In contrast to the high level of maturity of CE-5 regolith, the regolith breccias are immature, as judged by their low agglutinate (~11 vol%) and moderate to low matrix contents (~49 vol%). The CE-5 regolith breccias comprise mainly mare (~90 vol%) and non-mare (~10 vol%) materials. A low-Ti mare component of late Imbrian to early Eratosthenian age is identified, in addition to the predominant late Eratosthenian basalts in mare components. Non-mare components include Mg-suite norite, highland impact melt clasts, glass particles, and minor fragmented minerals. The glass particles in the CE-5 regolith breccias are compositionally variable and can be divided into five types, that is, basaltic (mare), KREEP-rich, feldspathic (highland), Si-poor, and Si-K-rich glasses. Among these glasses, most (65%) are compositionally exotic to the site. The diverse provenance of these “exotic” materials in the CE-5 breccias is consistent with the multiple ages of Zr-bearing phases at 3.97–3.92 Ga, ~3.2 Ga, 2.93–2.40 Ga, and ~2.0 Ga, in which early Eratosthenian ages are reported for the first time from returned lunar samples. The contrast in the level of maturity and in glass composition between CE-5 regolith and regolith breccias can be reconciled if CE-5 regolith breccias represent an ancient soil and were excavated from a buried stratigraphic sequence by later impacts. The duration of exposure of this old soil was short (<250 Myr), and its maturation was interrupted by late Eratosthenian basaltic magmatism.

^1,2Le Zhang; Ya-Nan Yang,^1,2Jintuan Wang,^1,2Ze-Xian Cui,^1,2Cheng-Yuan Wang,^1,2Peng-Li He,^1,2Yan-Qiang Zhang,^1,2Mang Lin,^1,2Yi-Gang Xu
American Mineralogist 110, 1462-1471 Link to Article [https://doi.org/10.2138/am-2024-9577]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Silicate liquid immiscibility was a common mechanism during the late-stage evolution of lunar basaltic magmas, which produced coexisting and immiscible Si- and Fe-rich melts. However, the relationship between silicate liquid immiscibility and lunar granitic rocks is debated. In this study, we investigated Si-rich melt inclusions hosted in fayalite fragments from lunar soil returned by the Chang’e 5 mission. These melt inclusions have high SiO2 (76.4 wt%), Al2O3 (11.1 wt%), and K2O (5.8 wt%), and low FeO (2.8 wt%), TiO2 (0.42 wt%), and MgO (0.02 wt%) contents. The texture and chemical composition indicate that these Si-rich melt inclusions formed through late-stage silicate liquid immiscibility of the Chang’e 5 mare basaltic magma. Mass balance considerations show that the unfractionated rare earth element patterns and Eu anomalies of these melt inclusions are similar to those of lunar granitic rocks. Dynamic calculations indicate that the accumulation of Si-rich melt was hindered by the high cooling rate of the Chang’e 5 basaltic magma after eruption. However, in deep-crustal magma chambers, basaltic magma would have cooled slowly, and the Si-rich melt generated by late-stage silicate liquid immiscibility would possibly have had enough time to migrate upward and accumulate to form a granitic melt body of significant size. The results of this study support the possibility that lunar granitic rocks are products of silicate liquid immiscibility.

^1,2Guangliang Zhang et al. (>10)
Earth and Planetary Science Letters 670, 119613 Link to Article [https://doi.org/10.1016/j.epsl.2025.119613]
¹Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
²University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

The Chang’e-4 mission lander and the rover landed in the Von Karman impact crater in the South Pole Aitken (SPA) basin on the far side of the moon. Using the optical images and spectral data obtained from 57 exploration points during the 60 lunar months by the Chang’e-4 rover, we have acquired information on the shallow structure of the lunar soil and the composition of the lunar surface materials. The results show that the main demonstration types in the landing area are basalt, weathered deposits, and highland rocks. The lunar soil layer in the landing area can be divided into two categories in terms of surface morphology and deep thickness, namely, thin layer lunar soil with light gray, less gravel, and less alteration, and thick layer lunar soil with dark color, more gravel, and more alteration. It was found that they alternate and appear as strip like structures, extending in a northeast southwest direction. At the same time, research on spectral composition data shows that its composition is uniform, and the composition of the landing zone is consistent with that of the Finsen impact crater, but it contains more olivine and glass components. The shallow radar research results show that the deep part of the landing area is divided into four layers: weathered accumulation layer, gravel layer, coarse gravel layer, basalt basement layer, and bedrock layer. Based on the above results, we found that the landing zone can be divided into the following stages after the formation of the Von Kármán impact crater: the Imbrian basalt filling period, during which the basalt bedrock at the bottom of the Von Kármán impact crater was formed; Next is the Eratosthenian impact modification period, during which large impact craters were formed around it, and the Von Kármán impact crater was modified. The ejecta from nearby impact craters contributed to the accumulation and weathering products of the landmass to a certain extent.

¹Anna Musolino, ¹Pierre Rochette, ^2,3Jean-Alix Barrat, ⁴Fred Jourdan, ^4,5Bruno Reynard, ¹Bertrand Devouard, ¹Valerie Andrieu, ¹Jérôme Gattacceca, ¹Vladimir Vidal
Earth and Planetary Science Letters 670, 119600 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119600]
¹Aix Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
²Univ Brest, CNRS, Ifremer, IRD, LEMAR, Institut Universitaire Européen de la Mer (IUEM), rue Dumont d’Urville, 29280 Plouzané, France
³Institut Universitaire de France, Paris, France
⁴Western Australian Argon Isotope Facility, School of Earth and Planetary Sciences, John de Laeter Centre for Isotope Research and C-FIGS, Curtin University, GPO Box U1987, Perth WA6845, Australia
⁵Laboratoire de Geologie de Lyon, CNRS UMR 5276, Ecole Normale Superieure de Lyon, 46, Allee d’Italie, 69364 Lyon Cedex 7, France
Copyright Elsevier

This study re-evaluates the anomalous subgroup of australites known as high Na/K (HNa/K) tektites (Chapman and Scheiber, 1969). Although previous compositional and isotopic analyses suggested a distinct origin, the group has never been formally recognized as a separate tektite strewn field. We present new data from six HNa/K tektites, complementing the eight specimens already described. We conducted a comprehensive investigation, including petrographic (optical and electron microscopy, and micro-X-ray tomography), geochemical (major and trace element compositions, Sr-Nd isotopic composition, 40Ar/39Ar dating), and spectroscopic (for the identification of inclusions) analyses. We concluded that the HNa/K tektites originated from a separate impact event compared to Australasian tektites; they have an andesitic to dacitic composition and arc-related trace element signatures. Lechatelierite (and phosphate) inclusions as well as high levels of chondritic contamination support an impact origin, for which we provide a more precise 40Ar/39Ar age: 10.76 ± 0.05 Ma. For now, Sr-Nd isotopic data and trace elements composition point to three possible sources associated with active volcanic arcs: Luzon (Philippines), Sulawesi (Indonesia), and the Bismarck region (Papua New Guinea). Systematic petrographic and geochemical differences observed between tektites from the western and eastern parts of the ∼900-km-wide hypothesized strewn field (located in Southern Australia) may help to constrain the location of the source crater, but they need to be confirmed by the study of more specimens. We propose the name “Ananguite” for this new group of tektites.

¹Courtney Jean Rundhaug, ¹Martin Schiller, ¹Martin Bizzarro, ^1,2Zhengbin Deng, ^3,4,5Hermann Dario Bermúdez
Earth and Planetary Science Letters 670, 119599 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119599]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen K, Denmark
²Deep Space Exploration Laboratory/CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
³Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043, USA
⁴Grupo de Investigación Paleoexplorer, 1400-37 Trexlertown Rd, PA 18062, USA
⁵Departamento de Geociencias, Universidad Nacional de Colombia, Bogotá 11001, Colombia
Copyright Elsevier

The Cretaceous-Paleogene boundary (KPB) represents a massive extinction event in Earth’s history, probably triggered by the Chicxulub asteroid impact ∼66 Ma. The event dispersed vast volumes of ejecta materials including exceptionally preserved impact spherules in the Gorgonilla Island KPB section. Previous work identified three populations of spherules at Gorgonilla: 1) ballistically transported molten spherules, 2) a mixture of molten and condensed spherules dispersed by the expansion of a high-temperature, turbulent cloud (the “pyrocloud”), and 3) tiny droplets condensed from the plume (the “fireball layer”). We determine the Mg, Fe, and Ca isotopic compositions of pristine spherules to better understand the evaporation and condensation thermodynamics within the pyrocloud. We detect enrichment in mass bias corrected µ48Ca and µ26Mg* isotope signatures from the terrestrial value corresponding to an impactor contribution of ∼17–25%, most likely from a CM or CO chondrite-like asteroid. The mass-dependent δ25Mg and δ56Fe compositions are generally light or unfractionated, suggesting incomplete recondensation as the pyrocloud cooled and expanded. Combined δ25Mg and δ56Fe signatures reveal decoupling of these isotope systems, likely due to differing condensation rates. Thus, we calculate a higher average condensation rate of Fe than Mg, reflecting the thermodynamic decoupling and more complete recondensation signatures of Fe in the pyrocloud vapor. While we uncover information about the evaporation and condensation thermodynamics in the pyrocloud, the exact formation mechanisms of the complete suite of spherules remain complex with some spherules potentially forming from multiple mechanisms, including recondensation and splash–melting.

^1,2Le Zhang,^1,2Ya-Nan Yang,^1,2Jintuan Wang,^1,2Ze-Xian Cui,^1,2Cheng-Yuan Wang,^1,2Peng-Li He,^1,2Yan-Qiang Zhang,^1,2Mang Lin,^1,2 Yi-Gang Xu
American Mineralogist 110, 1462-1471 Link to Article [https://doi.org/10.2138/am-2024-9577]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Silicate liquid immiscibility was a common mechanism during the late-stage evolution of lunar basaltic magmas, which produced coexisting and immiscible Si- and Fe-rich melts. However, the relationship between silicate liquid immiscibility and lunar granitic rocks is debated. In this study, we investigated Si-rich melt inclusions hosted in fayalite fragments from lunar soil returned by the Chang’e 5 mission. These melt inclusions have high SiO2 (76.4 wt%), Al2O3 (11.1 wt%), and K2O (5.8 wt%), and low FeO (2.8 wt%), TiO2 (0.42 wt%), and MgO (0.02 wt%) contents. The texture and chemical composition indicate that these Si-rich melt inclusions formed through late-stage silicate liquid immiscibility of the Chang’e 5 mare basaltic magma. Mass balance considerations show that the unfractionated rare earth element patterns and Eu anomalies of these melt inclusions are similar to those of lunar granitic rocks. Dynamic calculations indicate that the accumulation of Si-rich melt was hindered by the high cooling rate of the Chang’e 5 basaltic magma after eruption. However, in deep-crustal magma chambers, basaltic magma would have cooled slowly, and the Si-rich melt generated by late-stage silicate liquid immiscibility would possibly have had enough time to migrate upward and accumulate to form a granitic melt body of significant size. The results of this study support the possibility that lunar granitic rocks are products of silicate liquid immiscibility.