^1,2Andrea Patzer,¹Emma S.Bullock,¹ConelM. O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.021]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Rd. NW, Washington D.C. 20015, USA
²Geosciences Center, University of Goettingen, Goldschmidtstr. 1, 37077 Goettingen, Germany
Copyright Elsevier

Knowing how the major chondritic components evolved and what their initial compositions were is pivotal for our understanding of the processes that shaped the early Solar System. Here, we have extended to the CR chondrites our testing of chondrule-matrix complementarity and the four-component model, i.e., two very different explanations for the bulk compositions of the carbonaceous chondrites and their components. Combining point-counting with electron microprobe analyses, we have analyzed four relatively primitive Antarctic CRs and the fall Renazzo. Our results for the abundances of chondrules and matrix are in good agreement with literature data, and confirm that these abundances vary considerably amongst the CRs (80.4 ±2.3 wt.% and 18.5 ±2.8 wt.%, respectively, in the four Antarctic CRs vs. 62.3 ±3.4 wt.% and 33.2 ±2.2 wt.% in Renazzo). The significant differences make the determination of the average properties and bulk compositions of the CRs problematic. This is particularly true for the volatile elements that were predominantly accreted in matrix. Nevertheless, all major and many minor element concentrations reported in the literature for average bulk CRs are reproduced here to better than 10 %. By comparing our results to conventionally determined bulk compositions, we were able to verify the accuracy of our approach and identify elements likely affected by alteration or analytical artifacts (e.g., Ti, K, Co). Two particular compositional details of the CR chondrites investigated are (a) the relatively high contents of Mn in the chondrules compared to CO chondrules, and (b) the depletion of S in the matrix, relative to CI. In terms of the major elements Mg, Al, Si and Ca, our data suggest that unaltered chondrules and matrix exhibited CI-like relative abundances, supporting previous conclusions for the CO chondrites. Where observed, deviations of element abundances in the matrix from CI (Na, Mg, S, Ca, Fe, Ni) can be explained in terms of alteration (parent body and terrestrial) and pre-accretionary loss of forsterite and, possibly, sulfides. Overall, our results are more consistent with the predictions of the four-component model than they are with chondrule-matrix complementarity.

¹Maxence Regnault,¹Yves Marrocchi,¹Maxime Piralla,¹Johan Villeneuve,²Valentina Batanova,¹Nicolas Schnuriger,³Emmanuel Jacquet
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13778]
¹CRPG, UMR 7358, Université de Lorraine, CNRS, Vandœuvre-lès-Nancy, 54501 France
²ISTerre, UMR 5275, CNRS, Université Grenoble Alpes, Grenoble, 38000 France
³IMPMC, UMR 7590, CNRS & Muséum national d’Histoire naturelle, CP52, 57 rue Cuvier, Paris, 75005 France
Published by arrangement with John Wiley & Sons

Rumurutiites (R chondrites) are rare, highly oxidized chondrites belonging to the noncarbonaceous superclan and characterized by low chondrule abundances. Although textural and chemical features of Rumurutiite chondrules resemble those of ordinary chondrites (OCs), their formation conditions and potential genetic link remain debated. Here, we report high-resolution elemental X-ray mapping analyses and in situ O isotopic measurements of olivine grains from five chondrules and eight isolated olivine grains (IOGs) in the NWA 12482 R3 chondrite. The chondrules show chemical zonings similar to their counterparts in ordinary and carbonaceous chondrites (CCs), implying that gas–melt interaction processes between chondrule precursors and SiO- and Mg-rich gas were operative throughout the circumsolar disk. Our isotopic data show that R chondrules are isotopically similar to ordinary chondrules, although differences in their abundances of relict olivine grains and chondrule textural characteristics suggest different formation environments, with R chondrules being formed from 16O-poorer precursors. As with chondrules in OCs, the O isotopic characteristics of R chondrules and IOGs suggest limited transport between CC and noncarbonaceous reservoirs.

¹Hideyuki Hayashi,²Takashi Mikouchi,³Nak Kyu Kim,³Changkun Park,^4,5Yuji Sano,^6,7Atsushi Takenouchi,⁶Akira Yamaguchi,⁸Hiroyuki Kagi,⁹Martin Bizzarro
Meteoritics & Planetary Science (in Press) Link to Article [https://onlinelibrary.wiley.com/doi/10.1111/maps.13776]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
²The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
³Division of Earth Sciences, Korea Polar Research Institute (KOPRI), 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990 Korea
⁴Atmosphere and Ocean Research Institute (AORI), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8564 Japan
⁵Center for Advanced Marine Core Research, Kochi University, Monobe, Nankoku, Kochi, B200 783-8502 Japan
⁶Antarctic Meteorite Research Center, National Institute of Polar Research (NIPR), 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518 Japan
⁷The Kyoto University Museum, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto, 606-8501 Japan
⁸Geochemical Research Center, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
⁹Centre for Stars and Planet Formation, Globe Institute, University of Copenhagen, ØsterVoldgade 5-7, Copenhagen, DK-1350 Denmark
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 7203 is a quenched angrite, showing mineralogical features typically not present in other quenched angrites. NWA 7203 exhibits textures whose grain size varies from fine grains (<10 μm) to coarse grains (~3 mm), while other quenched angrites show only single-sized textures. Fine-grained and coarse-grained lithologies have nearly the same bulk compositions. Cooling rates were estimated to be ~80 °C h⁻¹ for fine-grained lithologies and ~1 °C h⁻¹ for coarse-grained lithologies. Mg-rich olivines (~Fo₆₄) were found only in fine-grained lithologies. Crystallization of NWA 7203 started in the fine-grained lithologies with Mg-rich olivine grains acting as seeds for crystallization. Coarse-grained lithologies were subsequently formed under conditions of slower cooling. NWA 7203 shows clear shock metamorphic textures unlike other quenched angrites except for NWA 1670. We confirm that the oxygen isotopic ratios of NWA 7203 plot on the angrite fractionation line within uncertainty. However, the obtained Pb-Pb age of NWA 7203 is 4543 ± 19 Ma, younger than the ages of other quenched angrites, which might be a result of disturbance by shock metamorphism. The finding of shock metamorphism of NWA 7203 suggests that some angrites might be derived from asteroids that remained large (>10 km in diameter) during the late heavy bombardment.

¹Liubov V. Guda,¹Antonina N. Kravtsova,²Stanislav P. Kubrin,¹Alexander A. Guda,³Mikhail I. Mazuritskiy,¹Andrei A. Tereshchenko,⁴Yuri V. Popov,¹Alexander V. Soldatov
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13769]
¹The Smart Materials Research Institute, Southern Federal University, A. Sladkova str. 178/24, Rostov-on-Don, 344090 Russia
²Research Institute of Physics, Southern Federal University, Stachki ave. 194, Rostov-on-Don, 344090 Russia
³Physics Faculty, Southern Federal University, Sorge str. 5, Rostov-on-Don, 344090 Russia
⁴Institute of Earth Sciences, Southern Federal University, Sorge str. 40, Rostov-on-Don, 344090 Russia
Published by arrangement with john Wiley & Sons

Micro X-ray fluorescence (XRF) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Mössbauer and X-ray absorption near-edge structure (XANES) spectroscopies have been used to study the element and phase composition, and Fe and Ni oxidation states in ordinary chondrites. The meteorites have been initially classified as Markovka (H4 type), Polujamki (H4 type), Sayh al Uhaymir (SaU) 001 (L5 type), Dhofar (Dho) 020 (H4/5 type), and Jiddat al Harasis (JaH) 055 (L4-5 type). We have applied a set of spectroscopic methods to characterize and quantify the differences between samples. While the concentration of Fe in the meteorites is in agreement with the qualitative assignment of their types (L or H) made upon discovery, we observed extremely low Mg/Si and Al/Si values compared to the data published by Palme et al. (2014). Phase content of the meteorites has been studied by means of XRD, as well as by SEM and EDX. Mössbauer spectroscopy of Fe-containing phases has determined that Fe ions are present mainly in olivine and pyroxene phases in all studied samples. Goethite, hematite, and troilite phases were found in Markovka, Polujamki, and Sayh al Uhaymir 001, respectively. Markovka and Polujamki samples contained the largest concentration of Fe-Ni-Co metal grains. Fe and Ni K-XANES spectra were analyzed to estimate metal oxidation state in the chondrites and compared with the Mössbauer data. The multispectral data acquired in the present work are of importance for further understanding of meteoritic processes.

^1,2,3Zhuqing Xue,³Donald F. Welsh,³Clive R. Neal,⁴Long Xiao
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13767]
¹School of Marine Sciences, University of the Chinese Academy of Sciences, Beijing, 100049 China
²Center of Deep-Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071 China
³Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, 46556 USA
⁴School of Earth Sciences, China University of Geosciences, Wuhan, 430074 China
Published by arrangement with John Wiley & Sons

This paper represents a comprehensive crystal size distribution (CSD) study of ilmenite and plagioclase from 12 Apollo 11 basalts from four of the five compositional groups (Groups A, B1, B2, B3, and one unclassified basalt—Group “U” basalt 10062). Ilmenite was saturated in the magma at/before eruption, resulting in subsurface growth of phenocrysts (Group B1) and many small crystals upon eruption. Plagioclase always exhibits linear CSDs representing a single cooling regime in each sample, which is interpreted as crystallizing within isolated magma pockets late in the cooling of the erupted lava flow. Latent heat of crystallization and insulating effects of crystallized phases produced slower cooling and lower plagioclase nucleation densities. Exceptions are the Group B2 and B3 basalts, indicating relatively earlier crystallization of plagioclase on the lunar surface. Our study demonstrates that textures of the Apollo 11 basalts are a product of the interplay among cooling rate, bulk composition, and nucleation density during crystallization. Group A basalts have the highest cooling rates compared to the other Apollo 11 samples (except 10072,53), and were erupted through high effusion rates producing thick flows that underwent extended cooling that induced textural coarsening in both early crystallizing ilmenite and late-stage plagioclase. Group B1 lavas had the lowest effusion rates producing the thinnest flows. The Groups B2, B3, and U basalts are intermediate between these end members. Our approach can be used to define eruption environment, crystallization sequence, and cooling rate of samples collected on the Moon from non-bedrock sources.

Cosmochemistry Papers will be on a short christmas break. Many thanks for the continued interest in these times. We wish all our followers a Merry Christmas and Happy New Year !

¹A.A.Nemchin,²M.D.Norman,³M.L.Grange,⁴R.A.Zeigler,³M.J.Whitehouse,⁵J.R.Muhling,⁶R.Merle
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.013]
¹School of Earth and Planetary Sciences, Curtin University, Australia
²Research School of Earth Sciences, The Australian National University, Canberra ACT 2601, Australia
³Swedish Museum of Natural History, S-104 05 Stockholm, Sweden
⁴Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston Texas USA
⁵School of Earth Sciences, The University of Western Australia, 6009, Perth, Australia
⁶Department of Earth Sciences, Natural Resources and Sustainable Development, Uppsala University, Sweden
Copyright Elsevier

Glass beads formed by ejection of impact-melted lunar rocks and soils are an important component of lunar soils. These glasses range from 10’s of microns to up to a few cm in diameter and contain variable, but usually relatively low (several hundred ppb to a few ppm), quantities of U. Because Pb is a volatile element, it tends to be lost from the melts, so individual impact glasses can be dated by the U-Th-Pb isotopic systems. The presence of two additional Pb components in lunar glasses, likely linked to addition of lunar Pb to the beads during their residence on the lunar surface and from terrestrial laboratory contamination, require corrections to the data before accurate formation ages of the glasses can be determined. Here we report a U-Th-Pb isotopic and geochemical study of impact glasses from the Apollo 14 soil 14163, which documents multiple impacts into chemically diverse targets that can be linked to the main groups of rocks found on the Moon, i.e., mare basalts, highlands plagioclase-rich rocks, and KREEP (from high contents of K, REE and P) enriched rocks. The impact ages show a bimodal distribution with peaks at ∼3500-3700 Ma and <1000 Ma, similar to that obtained previously by 40Ar-39Ar dating of other suites of lunar regolith glasses. Our data suggest two predominant age peaks at ∼100 Ma and ∼500 Ma, with other statistically definable clusters of ages also possible. As Pb is relatively resistant to subsolidus diffusive loss in these glasses, the age clusters probably represent primary formation ages during impact events, although processes such as preferential preservation of young glasses and impact conditions necessary for production of regolith glasses need further quantification.

¹Jonathan A.Lewis,^1,2Rhian H.Jones
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.014]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131
²Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
Copyright Elsevier

Thermal metamorphism in undisrupted ordinary chondrite (OC) parent bodies is thought to occur through the radioactive decay of 26Al, producing an onion-shell-like structure with higher peak metamorphic temperatures corresponding to increasing depth. During retrograde metamorphism, the onion-shell model predicts slower cooling rates with increasing petrologic type. However, cooling rates determined by pyroxene diffusion, metallographic, and other methods are inconsistent with onion-shell-like cooling, leading to a model of asteroid disruption and reaccretion into a rubble pile, after peak metamorphism. Potassium-feldspar exsolution in albite, in a perthite texture, has been noted in OCs and can be used as another method for determining cooling rates. We conducted a survey of K-feldspar occurrences and textures, within chondrules, in petrologic type 3.6-6 H, L, and LL OCs. Potassium-feldspar is present as a secondary feature, in primary and secondary albite, as fine-scale exsolution lamellae, 0.1-1.5 μm wide, as well as in larger patches up to 50 μm in size. Exsolution is present in all OC groups and is most common in petrologic type 4.

In the H4 chondrite Avanhandava, we estimate the cooling rate from perthite to be 3-17 °C/yr over a temperature interval of 765-670 °C. Peristerite is also present in Avanhandava for which we estimate a cooling rate of 0.2-2.4×10-3 °C/yr from 570-540 °C. In general, the relatively fast, high-temperature cooling rate determined by perthite is similar to cooling rates recovered from two-pyroxene speedometry. The peristerite cooling rate is closer to the slow, lower temperature metallographic cooling rates. Because K-feldspar exsolution is present in similar fine-scale lamellae in all OC groups, we suggest that all OC parent bodies experienced the same cooling history at high temperatures. These results are inconsistent with predictions of OC asteroid cooling from undisturbed onion-shell metamorphism but are consistent with models involving disruption after peak metamorphism followed by reassembly.

¹Conel M. O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.012]
¹Earth and Planets Laboratory, 5241 Broad Branch Road, NW, Washington DC 20015, USA
Copyright Elsevier

Here, two of a range of possible models are explored that assume that: (i) two of the main chondritic components (chondrules and refractory inclusions) dominated the Earth’s building blocks, (ii) that their relative abundances differed from those of known chondrites, and (iii) that the elemental compositions of all components, as well as the isotopic compositions of refractory inclusions, resembled those of the components in carbonaceous chondrites.

In terms of the elemental abundances, the chondrules can explain the moderately volatile element fractionations in the bulk silicate Earth (BSE), except for a few elements like F and In, while the refractory inclusions explain the BSE’s refractory lithophile element enrichment. Accretion of a CM- or EL-like late veneer reproduces the S, Se, Te and highly siderophile element abundances in the BSE. The accretion of CI- or CM-like material prior to the late veneer, along with small amounts of cometary and implanted solar wind material, can explain the BSE elemental and isotopic abundances of the noble gases as well as the elemental abundances of most other highly volatile elements (e.g., H, C and N) provided that variable fractions of them can be sequestered into the core or into hidden mantle reservoirs. This CI- or CM-like material provides an upper limit for the contribution to the BSE from matrix that is much less than in any chondrites. In the models, Si, O and S are the dominant light elements in the core, in that order, and their abundances are constrained to be consistent with the first principles calculations of Umemoto and Hirose (2020). The core compositions of the models are also consistent with most geochemical constraints.

Satisfying all isotopic constraints is a challenge. The BSE Os isotopes are consistent with an EL dominated late veneer, but Ru isotopic evidence is best explained by the addition of CM-like material in the late veneer. Either CI- or CM-like material, in combination with small amounts of cometary and implanted solar wind material, can reproduce the BSE Ne, Ar and Kr isotopic compositions. CM-like, but not CI-like, material can roughly reproduce the BSE’s H and C isotopic compositions, but neither material can explain the BSE N isotopic composition. The BSE composition requires that the O isotopic compositions of the refractory inclusions (initially Δ17O≤-20 ‰) in Earth’s building blocks were reset in the nebula by interaction with high Δ 17O H2O, perhaps during chondrule formation. To plot on the inner Solar System ε54Cr vs. ε 50Ti (or ε 48Ca) trend, either the average Cr content of the chondrules was roughly half of that assumed here or most of the CI/CM-like and refractory-inclusion-rich materials were accreted late.

¹Sandrine Péron,¹Sujoy Mukhopadhyay,²Mark D. Kurz,³David W. Graham
Nature 600, 462-467 Link to Article [DOI
https://doi.org/10.1038/s41586-021-04092-z%5D
¹Department of Earth and Planetary Sciences, University of California, Davis, Davis, CA, USA
²Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
³College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA

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