¹S. Alwmark,¹J. Granbom,¹P. Ahlberg,¹M. Calner,¹S. Richoz,¹K. J. Gajewska,¹W. R. Hyde,¹K. Ljung,¹C. Alwmark
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70160]
¹Department of Geology, Lund University, Lund, Sweden
Published by arragement with John Wiley & Sons

Hummeln is a simple impact structure located in south-eastern Sweden. It is approximately 1.2 km in diameter and almost completely covered by a lake. Here, we present the first detailed investigation of impactites and mapping of the 164.25 m deep drill core Hummeln-1 with a focus on impact metamorphism and the impact process. We find that the drilling has penetrated a complex sedimentary succession representing syn- to postimpact crater fill. It consists of (from base to top) lithic impact breccia (Unit 1), overlain by diamictite and graywacke with an overall fining upward trend grading from sandy into silty to clayey turbidites (Units 2, 3), and, lastly, suspension dominated marine clays and limestone (Units 4, 5). The crater fill was deposited mostly as gravity slides and sediment gravity flows (debris flows, (hyper)concentrated density flows and turbidity flows), which transported sediment into the crater as a series of fan lobes prograding toward the crater center. We have identified shocked quartz in 12 samples covering the interval of 160.69–56.60 m in the drill core and in samples of polymict and suevitic breccia obtained during fieldwork. Shocked quartz grains dominantly record planar fractures (PFs), with an average of 1.5–3.5 sets per grain. We measured a total of 122 PF sets in 54 grains, with orientations parallel to the $$, (0001), and $$ orientations being most common (30%, 26%, 21%, respectively). In the same samples, we also measured and indexed 14 sets of planar deformation features (PDFs) in eight grains, oriented parallel to the basal plane (50%), as well as rhombohedral planes $$, $$, and $$ (21%, 21%, and 7%, respectively). Feather features occur associated with PFs in seven of the samples. The quartz grains with shock microstructures in the drill core occur exclusively in beige graywacke–diamictite interbedded with the basal lithic breccia unit and in distinct graywacke–diamictite beds in the late syn- to early postimpact crater fill. We suggest that Hummeln was formed just prior to the deposition of parallel bedded marine mudrock with trilobites of the species Ellipsocephalus polytomus, indicating an early “middle” Cambrian (Wuliuan) age for the impact.

^1,2Zhong-Sha Meng,^1,3Ying-Kui Xu,^1,3Shi-Jie Li,^3,4Dan Zhu,^1,2De-Liang Wang,^1,3Yang Li,^1,3Xiong-Yao Li,^1,3Jian-Zhong Liu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70171]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, 230026, China
⁴State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences,Guiyang, 550081, China
Published by arrangement with John Wiley & Sons

Meteorite finds are commonly used to assess the chemical and isotopic compositions of their parent bodies. Among these, lithium (Li) isotopes in ordinary chondrites (OCs) have been applied to infer the Li abundance and isotopic characteristics of their parent bodies. However, Li is highly mobile in aqueous conditions and readily undergoes isotopic fractionation during fluid–mineral interactions. It remains uncertain whether Li isotopic compositions in meteorite finds reliably preserve their original parent-body signatures, particularly after prolonged terrestrial exposure. In this study, we investigated Li isotope behavior in Kumtag 015 (W3, L5) by conducting a series of leaching experiments. The untreated whole-rock sample yields a δ7Li value of +6.1‰, whereas all leachates exhibit heavier δ7Li values, ranging from +8.4‰ to +14.8‰, indicating the presence of weathering-related secondary components enriched in heavy Li isotopes. Combined with the petrographic observations and mass-balance results, these data suggest that the relatively heavy whole-rock δ7Li of Kumtag 015 is mainly related to the addition of heavy-δ7Li surficial fluids during terrestrial weathering, followed by the sequestration of Li into secondary minerals such as carbonates and Fe-(oxyhydr)oxides. This finding is consistent with prior work showing heavy δ7Li in carbonates. We conclude that terrestrial alteration can substantially modify Li isotope compositions in meteorite finds, highlighting the need for caution when using such samples to trace pristine planetary Li inventories.

¹Allan H. Treiman
American Mineralogist 111, 1009-2021 Link to Article [https://doi.org/10.2138/am-2025-9919]
¹Lunar and Planetary Institute (USRA), 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Society of America

The nakhlite martian meteorites, basaltic rocks with abundant crystals of augite pyroxene, have been interpreted as cumulates, having formed as crystals of augite (and olivine) settled through basalt magma to accumulate at its bottom. Here, I show that the chemical compositions of most nakhlites are best explained if they represent magmas, and not crystal accumulates. The nakhlites Nakhla, Lafayette, and Y000593 are identified as cumulates; the rest are magmas. Among the magma nakhlites, abundances of all igneous incompatible elements are strongly correlated; abundances of highly incompatible elements are linearly correlated with the La/Yb ratio, with R2 values from 0.7 to 0.95. These close correlations are not consistent with the group being cumulates, where the proportion of cumulus augite should be mostly independent of magma composition. Instead, the correlations are consistent with the nakhlites representing magmas, with the range of compositions reflecting processes including: variable enrichment in incompatible elements (i.e., metasomatism) in the source mantle; variable degrees of partial melting of the source mantle; and mixing among such magmas. Significant crustal assimilation (for the tested elements) is excluded by the correlation of Al with La/Yb. The most Al-rich nakhlite would require assimilation of 25% mass crust into the Al-poorest, which is inconsistent with thermochemical constraints. Recognition of such augite-rich, pyroxenitic magmas requires that their mantle source be similarly pyroxenitic, which implies that the martian mantle is more heterogeneous than previously appreciated.

Cosmochemistry Papers will be on a short spring break next week, service will commence again on 01.06.

¹Simone Pascucci et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70170]
¹Institute of Methodologies for Environmental Analysis (IMAA)-Italian National Research Council (CNR), Tito Scalo, Italy
Published by arrangement with John Wiley & Sons

Asteroid compositional analysis relies on comparing reflectance spectra with laboratory data from well-characterized meteorites. To advance this comparison, we performed a comprehensive laboratory analysis on a slab of the Northwest Africa (NWA) 7317—CR6 carbonaceous chondrite. We employed high-resolution Visible-Infrared (VIS-IR) imaging spectroscopy (0.4–5.1 μm) using the SPIM hyperspectral facility, integrated with high-spatial-resolution elemental mapping via SEM-EDS and EMPA-WDS. This multi-technique approach enabled the retrieval of surface composition at high spectral and spatial resolutions. Our results, supported by ICA/PCA and K-means classification methodologies, highlight the challenges of integrating VIS-IR spectroscopy and SEM/EMPA at the micrometer scale. While both techniques consistently infer an overall poikiloblastic/metamorphic texture dominated by an olivine and pyroxene-rich matrix, their combined use requires a critical approach for robust analysis. The absence of the 3 μm absorption band indicates high temperatures during thermal metamorphism on the NWA 7317 parent body. Although FeNi metallic alloys and Fe-sulfide inclusions contribute to the VIS-IR spectroscopic signal, they are not clearly distinguishable from each other. Furthermore, minor phases like plagioclase and chromite detected via SEM/EMPA are not plainly visible in the SPIM results. We review the potential of integrating these techniques to assess the petrography, mineralogy, and terrestrial weathering of NWA 7317.

¹Christina Hamilton,²Shannon Dulin,³John Weber,²R. Douglas Elmore
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70139]
¹BP, Houston, TX, USA
²School of Geosciences, University of Oklahoma, Norman, Oklahoma, USA
³Department of Geology, Grand Valley State University, Allendale, MI, USA
Published by arrangement with John Wiley & Sons

A paleomagnetic and petrographic study of host carbonate rocks and impact breccias at the Kentland impact structure was conducted to better constrain the timing of the impact and to test for alteration by hydrothermal fluids. The Ordovician-Silurian target rocks sampled are fossiliferous wackestone/packstones with minor dolomite. Polymict impact breccias, also sampled, occur as dikes/sills and contain clasts of dolomite, host carbonate, sandstone, sphalerite, and rare coated grains which contain clays, dolomite, calcite, and hexagonal silica resembling tridymite. The host carbonates contain brecciated zones near the polymict breccias that display flow textures of aligned and elongated clasts and minerals. Authigenic minerals present include sylvite, apatite, gypsum, magnetite, and hematite. These observations suggest alteration by hydrothermal fluids, which probably had an estimated duration of ~7500 yrs after impact. Alternating field (AF) and thermal demagnetization of impact breccia and host carbonate specimens removed two post-tilting magnetic components: one with southerly declinations and moderate negative inclinations and the other with northerly declinations and positive inclinations. Demagnetization results suggest the magnetizations primarily reside in magnetite as well as hematite and possibly pyrrhotite. Petrographic and rock magnetic results are consistent with this interpretation. These magnetizations are interpreted as chemical remanent magnetizations acquired through a reversal, which formed from alteration by hydrothermal fluids generated after the impact. The paleomagnetic poles (mean pole, 75.7° N, 98.4° W) fall near the Early Jurassic part of the apparent polar wander path, which suggests the alteration in the breccias, and likely the impact, occurred in the Early Jurassic (175–185 Ma).

^1,2Jin Yu Zhang,^1,2Hong Yi Chen,^1,2Yi Man Yin,^1,2Lan Fang Xie,^1,2Xu Kai Gao,²Xi Jun Liu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70164]
¹Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution of GuangxiProvincial Universities, Guilin University of Technology, Guilin, China#
²Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, China
Published by arragement with John Wiley & Sons

The Maoming meteorite, which fell in Guangdong Province, China, on May 28, 2025, represents the second-largest witnessed meteorite recovery event in China since 1949, with a total recovered mass of 423 kg. This study presents an integrated analysis of its petrology, mineral chemistry, and aerodynamic behavior to reconstruct the complete atmospheric entry-to-impact sequence. Fresh samples were examined using optical microscopy, electron probe microanalysis, and density measurements, while the entry trajectory was simulated using a fourth-order Runge–Kutta model constrained by impact crater morphology and atmospheric data. Based on mineralogical homogeneity and shock-weathering features, Maoming is classified as an L5 ordinary chondrite (shock stage S3, weathering grade W1) with a double-layered fusion crust indicating peak temperatures of 1410°C–1615°C. Aerodynamic modeling, based on a constrained initial velocity of ~15 km/s, yields an entry angle of 13.9° and a terminal impact velocity of 267.23 m/s at a trajectory angle of 65°. The simulated penetration depth (2.98 m) closely matches field observations (~3 m), validating the reconstructed dynamics. Despite its friable, fractured structure, the meteoroid survived atmospheric passage without catastrophic disruption, contrasting with typical fragmentation-dominated entries. This case provides critical empirical constraints on the survival of moderately strong, fractured ordinary chondrites under moderate entry conditions. The combined petrological and aerodynamic approach presented here provides a framework for rapid trajectory reconstruction and impact effect quantification. This framework also offers empirical constraints on the trajectory and cratering mechanics of meter-scale, moderately strong meteoroids.

^1,2Louis-Alexandre Lobanov,^1,2Hilary Downes
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70146]
¹Natural History Museum, London, UK
²School of Natural Sciences, Birkbeck University of London, London, UK
Published by arrangement with John Wiley & Sons

Iron meteorites are usually classified manually using bivariate elemental plots. This study extends iron meteorite classification into multi-element space. We present a computational method for the classification of iron meteorites by applying unsupervised machine learning using density-based cluster analysis. It provides formatted iron meteorite data extracted manually from 61 papers, as well as the software created for the application of cluster analysis to iron meteorites. The method can be used to speed up and standardize iron meteorite classification, reduce bias, increase transparency, and check reproducibility of existing classifications. It is fully scalable and can use any number and combination of elements. It allows for the classification of new iron meteorites, checks the validity of existing classifications, and can identify ungrouped iron meteorites that may be related to existing groups. The model has been applied to ungrouped iron meteorites and 29 are suggested for reclassification based on our multi-element results.

¹S. S. Russell et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70151]
¹Planetary Materials Group, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

Aqueously altered carbonaceous astromaterials are dominated by secondary minerals, but a minor fraction of primary, anhydrous silicates and oxides escape alteration, offering insight into the original composition of asteroid parent bodies. We report the mineralogy, petrology, mineral chemistry, and oxygen isotopes of anhydrous minerals—50 olivine grains, 12 pyroxene grains, two spinel grains, and one hibonite grain—in aqueously altered particles returned from asteroid Bennu by the OSIRIS-REx mission. These primordial grains are heterogeneously distributed, being more abundant (up to a few area percent for olivine) in less aqueously altered clasts. Olivine is typically forsteritic (Fo100–Fo93), but we found three fayalitic examples (Fo80–Fo75). Of the pyroxenes, seven grains are enstatite (En100–En94); two are enstatite with more Fe (En83 and En87); one is Fe-rich, low-Ca clinopyroxene; one is Mg-rich, aluminous low-Ca pyroxene; and one is high-Al, Ca-rich clinopyroxene. Chromium is present in olivine grains at high abundances (up to 1.3 wt% Cr2O3), indicating that the grains have not experienced significant thermal metamorphism. The olivines fall into two clusters: one with 16O-rich compositions (δ18O = −43 to −51‰) typical of refractory inclusions in carbonaceous chondrites and one with comparatively 16O-poor compositions (δ18O = −11 to +7.5‰) more typical of chondrules. Pyroxenes all fall in the 16O-poor cluster (δ18O = −2.6 to +13.5‰). For both olivine and pyroxene, the more Fe-rich examples are associated with heavier oxygen isotope compositions. One isolated spinel grain has an oxygen isotope composition typical of Ca-Al–rich inclusions, whereas a spinel–hibonite object has an unusual oxygen isotope composition consistent with fractionated unknown nuclear (FUN) compositions. Together, our data suggest that Bennu’s parent body accreted a population of finer grained (≤10 μm) silicate and oxide grains that as a population are distinct from the anhydrous minerals in most chondrite groups but comparable to those in CI chondrites. The Bennu samples, as well as those from asteroid Ryugu and CI chondrites, appear to have accreted from a distinct reservoir that may have been in the outer protoplanetary disk.

^1,2Cheng-Yu Du, ^1,2Shao-Bing Zhang, ³Hejiu Hui, ¹Ting Liang, ¹Wan-Cai Li, ¹Yong-Fei Zheng
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.05.006]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
²Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
³State Key Laboratory for Mineral Deposits Research & Lunar and Planetary Science Institute, School of the Earth Sciences and Engineering, Nanjing University, Nanjing, China
Copyright Elsevier

China’s Chang’E-5 (CE-5) lunar mission retrieved the youngest known mare basalt with low magnesium number (Mg#) and high incompatible element contents. However, the nature of its mantle source remains debated. Here we carried out in-situ analyses of major and trace element contents in olivine and pyroxene for CE-5 basalt clasts to constrain the petrogenetic process and mantle source of CE-5 basalt. The results indicate that the pyroxene Ti# (molar Ti/(Ti + Cr)) rose sharply at an early stage into the high-Ti basalt field and subsequently remained constant, implying extensive fractional crystallization of the CE-5 basalt. The near constant Ti content in olivine records an early crystallization of ilmenite at an olivine Mg# of approximately 60. Calculated TiO2 and Cr2O3 contents of the melt equilibrated with the most forsteritic olivine yielded TiO2 content of 6.06 ± 0.77 wt% and Cr2O3 content of 0.516 ± 0.089 wt%. Pyroxene exhibits concurrent decreases in LREE/HREE ratios, Zr/Y ratio and Al content as its Mg# decreases, whereas the early decrease of olivine Zr/Y ratio indicates a primitive melt with high Zr/Y ratio. Integrating these findings with previously reported isotopic data, theoretical modelling supports a hybrid mantle source dominated by orthopyroxene cumulate, with a small proportion of ilmenite-bearing cumulate (IBC, 0.40–0.55%) and KREEP (0.11–0.15%). Such a source region supports a geodynamic mechanism for the young mare magmatism that the IBC-rich hot plume rises from the core-mantle boundary heating the upper mantle that contains small amounts of IBC and KREEP to melt.