^1,2Jean-Alix Barrat,³Addi Bischoff,⁴Brigitte Zanda
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.07.003]
¹Univ Brest, CNRS, UMR 6539 (Laboratoire des Sciences de l’Environnement Marin), Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, 29280 Plouzané, France
²Institut Universitaire de France, Paris
³Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
⁴Muséum National d’Histoire Naturelle, Laboratoire de Minéralogie et de Cosmochimie du Muséum, CNRS UMR7202, 61 rue Buffon, 75005 Paris, France
Copyright Elsevier

We report on new trace element analyses of enstatite chondrites (ECs) to clarify their behavior during the metamorphism. During the transition from a type 3 to a type 5 or higher, silicates lose a large portion of their trace elements to sulfides. Our procedure allows us to obtain trace element abundances of the silicate fraction of an EC quite easily. The element patterns of these fractions (especially REE patterns) are quite different for EH and EL chondrites, and are furthermore dependent on the metamorphic grade. This procedure can be usefull to classify meteorites, in particular when the sulfides are altered. Applied to anomalous ECs, it allows direct recognition of the EH affinity of QUE 94204, and suggests that Zakłodzie, NWA 4301, and NWA 4799 derive from the same EH-like body of previously unsampled composition.

We have used the concentrations obtained on the silicate fractions of the most metamorphosed chondrites to discuss the chemical characteristics of the primitive mantles of reduced bodies of EH or EL affinity (i.e., after core segregation). Our data indicate that these mantles are very depleted in refractory lithophile elements (RLEs), particularly in rare earth elements (REEs), and notably show significant positive anomalies in Sr, Zr, Hf, and Ti. These estimates imply that the cores contain most of the REEs, U and Th of these bodies. Interestingly, the inferred primitive mantles of these reduced bodies contrast with that of the Earth. If the Earth accreted essentially from ECs, one would expect similar signatures to be preserved, which is not the case. This mismatch can be explained either by a later homogenization of the bulk silicate Earth, or alternatively, that the materials that were accreted were isotopically similar to ECs, but mineralogically different (i.e., oldhamite-free).

¹Francis M. McCubbin,¹, Jonathan A. Lewis,², Jessica J. Barnes,¹, Jeremy W. Boyce,^1,3Juliane Gross, ⁴Molly C. McCanta,^5,6Poorna Srinivasan, ⁷Brendan A. Anzures,¹Nicole G. Lunning,¹, Stephen M. Elardo,¹Lindsay P. Keller,⁹Tabb C. Prissel,^5,6Carl B. Agee
American Mineralogist 108, 1185-1200 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1185.pdf]
¹NASA Johnson Space Center, Mailcode XI, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²Lunar and Planetary Laboratory, University of Arizona, 1629 E University Boulevard, Tucson, Arizona 85721, U.S.A.
³Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, U.S.A.
⁴Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, U.S.A. 5
⁵Institute of Meteoritics, University of New Mexico, 200 Yale Boulevard SE, Albuquerque, New Mexico 87131, U.S.A.
⁶Department of Earth and Planetary Sciences, University of New Mexico, 200 Yale Boulevard SE, Albuquerque, New Mexico 87131, U.S.A.
⁷Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
⁸Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, U.S.A.
⁹Jacobs, NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Socuety of America

We conducted a petrologic study of apatite within one LL chondrite, six R chondrites, and six CK
chondrites. These data were combined with previously published apatite data from a broader range of chondrite meteorites to determine that chondrites host either chlorapatite or hydroxylapatite with ≤33 mol% F
in the apatite X-site (unless affected by partial melting by impacts, which can cause F-enrichment of
residual apatite). These data indicate that either fluorapatite was not a primary condensate from the solar
nebula or that it did not survive lower temperature nebular processes and/or parent body processes.
Bulk-rock Cl and F data from chondrites were used to determine that the solar system has a Cl/F ratio of
10.5 ± 1.0 (3σ). The Cl/F ratios of apatite from chondrites are broadly reflective of the solar system Cl/F
value, indicating that apatite in chondrites is fluorine poor because the solar system has about an order
of magnitude more Cl than F. The Cl/F ratio of the solar system was combined with known apatite-melt
partitioning relationships for F and Cl to predict the range of apatite compositions that would form from
a melt with a chondritic Cl/F ratio. This range of apatite compositions allowed for the development of a
crude model to use apatite X-site compositions from achondrites (and chondrite melt rocks) to determine
whether they derive from a volatile-depleted and/or differentiated source, albeit with important caveats
that are detailed in the manuscript. This study further highlights the utility of apatite as a mineralogical
tool to understand the origin of volatiles (including H2O) and the diversity of their associated geological
processes throughout the history of our solar system, including at its nascent stage.

¹Christiaan P. A. van Buchem,^1,2Yamila Miguel,¹Mantas Zilinskas,³Wim van Westrenen
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13994]
¹Leiden Observatory, Leiden University, Leiden, The Netherlands
²SRON Netherlands Institute for Space Research, Leiden, The Netherlands
³Faculty of Science, Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
Published by arrangement with John Wiley & Sons

To date, over 500 short-period rocky planets with equilibrium temperatures above1500 K have been discovered. Such planets are expected to support magma oceans,providing a direct interface between the interior and the atmosphere. This provides a uniqueopportunity to gain insight into their interior compositions through atmosphericobservations. A key process in doing such work is the vapor outgassing from the lavasurface. LavAtmos is an open-source code that calculates the equilibrium chemicalcomposition of vapor above a dry melt for a given composition and temperature. Resultsshow that the produced output is in good agreement with the partial pressures obtainedfrom experimental laboratory data as well as with other similar codes from literature.LavAtmos allows for the modeling of vaporization of a wide range of different mantlecompositions of hot rocky exoplanets. In combination with atmospheric chemistry codes,this enables the characterization of interior compositions through atmospheric signatures.

¹Daisuke Nakashima,¹Yuri Fujioka,¹Kanchi Katayama,¹Tomoyo Morita,¹Mizuha Kikuiri,¹Kana Amano,¹Eiichi Kagawa,¹Tomoki Nakamura
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14036]
¹Department of Earth Science, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

Preparation procedures of polished sections of the Ryugu samples returned by theHayabusa2 spacecraft were established through tests using CI and CM chondrites as analogmaterials of the Ryugu samples and processing of the Ryugu samples. The proceduresconsisted of four steps: epoxy-coating, embedding in epoxy cylinders, cutting with a wiresaw, and dry polish by hand. There are three key points for successful preparation of thepolished sections: (1) ethanol-mixed epoxy with low viscosity for reinforcing the fragilesamples, (2) handling under dry conditions to avoid breakup of the samples on contact withliquids due to their highly porous nature, and (3) X-ray computed tomography data forexposing maximum surface areas of target mineral phases and clasts. These key points mayalso be important for processing of samples returned from asteroid Bennu and the MartianMoon Phobos, as those samples are likely to be hydrous carbonaceous chondrite-likematerials. The established procedures induce two side effects: zoning of the polished surfaceof the Ryugu samples in scanning electron microscope images reflecting differences incarbon contents due to permeation of low viscosity epoxy resin into the sample surface andfractures in anhydrous minerals possibly due to shear stress during dry polishing.

¹Teng Ee Yap,¹François L.H. Tissot
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115680]
¹The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
Copyright Elsevier

Nucleosynthetic isotope anomalies of planetary materials provide insight into their genetic ties, informing our understanding of early Solar System isotopic architecture and evolution. Isotope anomalies of non‑carbonaceous (NC) and carbonaceous (CC) materials in multi-element space suggests their variability primarily emerged from mixing between several primordial nebular source regions in the nascent protoplanetary disk. In particular, it has been suggested that the elemental and isotopic compositions of CC meteorites reflect admixtures of NC-like, CI-like, and CAI-like components. Despite the plethora of elements for which isotope anomalies have been characterized, no mixing model has quantitatively reproduced CC meteorite compositions for more than two elements.

In this paper, we leverage the recent characterization of Fe isotope anomalies in NC and CC materials, as well as CAIs, to place new constraints on the evolution of the early Solar System and the origin of the CC chondrites. We first respond to the recent proposal, based on Fe isotope analyses of returned samples from Cb-type asteroid Ryugu, that Ryugu and CI chondrites are genetically distinct from NC and CC bodies, originating from a third “CI reservoir” beyond the location of the CC reservoir. Namely, we propose that the appearance of such a trichotomy in meteoritic heritages arises from the current lack of Fe isotope data for CC achondrites. We go on to present a self-consistent mixing model that explains the Ti, Cr, Fe, and Ca concentrations and isotope anomalies of the CM, CV, CO, CK, and CR chondrite groups via admixing of (i) elementally OC-like material, (ii) CI/Ryugu-like material, (iii) isotopically CAI-like dust, and (iv) CAIs sensu stricto. We find that the CAI-like dust constitutes a major and broadly constant fraction (∼36%) of all CC chondrites, and identify the CI-like component with the bulk composition of the Solar System’s parent molecular cloud, denoting it BMC for “Bulk Molecular Cloud.” We interpret our results in the context of a qualitative model for early Solar System isotopic evolution.

¹Sota Arakawa,²Daiki Yamamoto,³Takayuki Ushikubo,⁴Hiroaki Kaneko,⁵Hidekazu Tanaka,¹Shigenobu Hirose,⁴Taishi Nakamoto
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115690]
¹Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan
²Department of Earth and Planetary Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
³Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe-otsu, Nankoku, Kochi, 783-8502, Japan
⁴Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo, 152-8550, Japan
⁵Astronomical Institute, Graduate School of Science, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, 980-8578, Japan
Copyright ELsevier

Oxygen isotope compositions of chondrules reflect the environment of chondrule formation and its spatial and temporal variations. Here, we present a theoretical model of oxygen isotope exchange reaction between molten silicate spherules and ambient water vapor with finite relative velocity. We found a new phenomenon, that is, mass-dependent fractionation caused by isotope exchange with ambient vapor moving with nonzero relative velocity. We also discussed the plausible condition for chondrule formation from the point of view of oxygen isotope compositions. Our findings indicate that the relative velocity between chondrules and ambient vapor would be lower than several 100ms−1 when chondrules crystallized.

^1,2,3M.D.Suttle et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.06.027]
¹Planetary Materials Group, Natural History Museum, Cromwell Road, London, SW7 5BD, UK]
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
³Dipartimento di Scienze della Terra, Università di Pisa, 56126 Pisa, Italy
Copyright Elsevier

We searched late Miocene sedimentary rocks in an attempt to recover fossil micrometeorites derived from the Veritas asteroid family. This study was motivated by the previous identification of a pronounced 3He peak (4-5x above background) within marine sediments with ages between ∼8.5-6.9 Ma ago (Montanari et al. 2017. GSA Bulletin, 129:1357-1376). We processed 118.9 kg of sediment from the Monte dei Corvi beach section (Italy), the global type-section for the Tortonian epoch (11.6-7.2 Ma). Samples were collected both before and within the 3He peak. Although a small number of iron-rich (I-type) fossil micrometeorites were recovered from each horizon studied (Ntotal = 20), there is no clear difference between the pre- and intra- 3He peak samples. All micrometeorites are compositionally similar, and three out of five horizons yielded similar abundances and particle sizes. Micrometeorites extracted from sediments at the base of the 3He peak were exclusively small (ø <75 µm), while micrometeorites extracted from sediments near the highest 3He values were relatively large (ø <270 µm). The recovered fossil micrometeorites are interpreted as samples of the background dust flux derived from metal-bearing chondritic asteroids. The presence of a 3He signature combined with the absence of fossil micrometeorites or extraterrestrial spinels (Boschi et al. 2019, Spec. Pap. Geol. Soc. Am. 542:383-391) unambiguously related to the Veritas event suggests that the Veritas family is composed of highly friable materials that rarely survive on the sea floor to become preserved in the geological record. Our data supports the existing hypothesis that the Veritas asteroid family is an aqueously altered carbonaceous chondrite parent body, one that contains minimal native metal grains or refractory Cr-spinels. The low yield of fossil micrometeorites at Monte dei Corvi is attributed to loss of particles by dissolution whilst they resided on the sea floor but also due to high sedimentation rates leading to dilution of the extraterrestrial dust flux at this site. As with other fossil micrometeorite collections (e.g. Cretaceous chalk [Suttle and Genge, EPSL, 476:132-142]) the I-type spherules have been altered since deposition. In most particles, both magnetite and wüstite remain intact but have been affected by solid state geochemical exchange, characterised by partial leaching of Ni, Co and Cr and implantation of Mn, Mg, Si and Al. In some particles Mn concentrations reach up to 16.6 wt.%. Conversely, in some micrometeorites wüstite has been partially dissolved, or even replaced by calcite or ankerite. Finally, we observe evidence for wüstite recrystallisation, forming a second generation of magnetite. This process is suggested to occur by oxidation during residence on the seafloor and has implications for the use of fossil I-type micrometeorites as a potential proxy for probing Earth’s upper atmospheric composition (oxidative capacity) in the geological past. However, solutions to the limitations of post-depositional recrystallisation are suggested. Fossil I-type spherules remain a potential tool for palaeo-climatic studies.

¹Jinia Sikdar, Harry Becker,²Jan A. Schuessler
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13990]
¹Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany
²Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Potsdam, Germany
Published by arrangement with John Wiley & Sons

Silicon and iron isotope compositions of different physically separated components of enstatite chondrites (EC) were determined in this study to understand the role of nebular and planetary scale events in fractionating Si and Fe isotopes of the terrestrial planet-forming region. We found that the metal–sulfide nodules of EC are strongly enriched in light Si isotopes (δ30Si ≥ −5.61 ± 0.12‰, 2SD), whereas the δ30Si values of angular metal grains, magnetic, slightly magnetic, and non-magnetic fractions become progressively heavier, correlating with their Mg# (Mg/(Mg+Fe)). White mineral phases, composed primarily of SiO2 polymorphs, display the heaviest δ30Si of up to +0.23 ± 0.10‰. The data indicate a key role of metal–silicate partitioning on the Si isotope composition of EC. The overall lighter δ30Si of bulk EC compared to other planetary materials can be explained by the enrichment of light Si isotopes in EC metals along with the loss of isotopically heavier forsterite-rich silicates from the EC-forming region. In contrast to the large Si isotope heterogeneity, the average Fe isotope composition (δ56Fe) of EC components was found to vary from −0.30 ± 0.08‰ to +0.20 ± 0.04‰. A positive correlation between δ56Fe and Ni/S in the components suggests that the metals are enriched in heavy Fe isotopes whereas sulfides are the principal hosts of light Fe isotopes in the non-magnetic fractions of EC. Our combined Si and Fe isotope data in different EC components reflect an inverse correlation between δ30Si and δ56Fe, which illustrates that partitioning of Si and Fe among metal, silicate, and sulfidic phases has significantly fractionated Si and Fe isotopes under reduced conditions. Such isotope partitioning must have occurred before the diverse components were mixed to form the EC parent body. Evaluation of diffusion coefficients of Si and Fe in the metal and non-metallic phases suggests that the Si isotope compositions of the silicate fractions of EC largely preserve information of their nebular processing. On the other hand, the Fe isotopes might have undergone partial or complete re-equilibration during parent body metamorphism. The relatively uniform δ56Fe among different types of bulk chondrites and the Earth, despite Fe isotope differences among their components, demonstrates that the chondrite parent bodies were not formed by random mixing of chondritic components from different locations in the disk. Instead, the chondrite components mostly originated in the same nebular reservoir and Si and Fe isotopes were fractionated either due to gas–solid interactions and associated changes in physicochemical environment of the nebular reservoir and/or during parent body processing. The heavier Si isotope composition of the bulk silicate Earth may require accretion of chondritic and/or isotopically heavier EC silicates along with cumulation of refractory forsterite-rich heavier silicates lost from the EC-forming region to form the silicate reservoir of the Earth.

^1,2,3,4Ryoga Maeda,¹Steven Goderis,⁵Akira Yamaguchi,⁶Thibaut Van Acker,⁶Frank Vanhaecke,²Vinciane Debaille,¹Phillippe Claeys
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14034]
¹Analytical-, Environmental-, and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
²Laboratoire G-Time, Université libre de Bruxelles, Brussels, Belgium
³Submarine Resources Research Center (SRRC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
⁴REE Smelting Unit, Development of Production Technology for REE, General Project Team for SIP, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
⁵National Institute of Polar Research, Tokyo, Japan
⁶Atomic & Mass Spectrometry (A&MS) Research Unit, Department of Chemistry, Ghent University, Ghent, Belgium
Published by arrangement with John Wiley & Sons

The chemical effects of terrestrial alteration, with a particular focus on lithophile trace elements, were studied for a set of H chondrites displaying various degrees of weathering from fresh falls to altered finds collected from hot deserts. According to their trace element distributions, a considerable fraction of rare earth elements (REEs), Th, and U resides within cracks observed in weathered meteorite specimens. These cracks appear to accumulate unbound REEs locally accompanied by Th and U relative to the major element abundances, especially P and Si. The deposition of Ce is observed in cracks in the case of most of the weathered samples. Trace element maps visually confirm the accumulation of these elements in such cracks, as previously inferred based on chemical leaching experiments. Because the positive Ce anomalies and unbound REE depositions in cracks occur in all weathered samples studied here while none of such features are observed in less altered samples including falls (except for altered fall sample Nuevo Mercurio), these features are interpreted to have been caused by terrestrial weathering following chemical leaching. However, the overall effects on the bulk chemical composition remain limited as the data for all Antarctic meteorites studied in this work (except for heavily weathered sample A 09516, H6) are in good agreement with published data for unaltered meteorites.

¹Miriam Rüfenacht,¹Précillia Morino,^1,2Yi-Jen Lai,¹Manuela A. Fehr,^1,3Makiko K. Haba,¹Maria Schönbächler
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.06.005]
¹Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, CH-8092 Zurich, Switzerland
²Macquarie GeoAnalytical, Faculty of Science and Engineering, Macquarie University, Sydney, 2109, NSW, Australia
³Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ishikawadai Building 2-105, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan
Copyright Elsevier

Nucleosynthetic isotope variations are powerful tools to investigate genetic relationships between meteorite groups and planets. They are instrumental to assess the early evolution of the solar system, including mixing and reservoir formation in the protoplanetary disk, as well as planet formation. To address these questions, we report high-precision nucleosynthetic Ti isotope compositions of a wide range of bulk meteorites, partially complemented with new Cr isotope data. New Ti isotope data confirm the first order dichotomy observed between carbonaceous chondrites (CC), representing outer solar system compositions, and non-carbonaceous (NC) meteorites from the inner solar system. The data in combination with nucleosynthetic isotope data of other elements (e.g., Cr, Ca) indicate that isotopically heterogeneous reservoirs were also present as sub-reservoirs in the inner disk (NC reservoir), generating two or more clusters i.e., (i) the Vesta-like howardites-eucrites-diogenites (HEDs), mesosiderites, angrites, acapulcoites, lodranites, and brachinites and (ii) the Earth-Mars-like ordinary chondrites (OC), aubrites, enstatite chondrites (EC), winonaites, IAB silicates, rumuruti chondrites (R), Martian and terrestrial samples. These reservoirs likely represent disk substructures such as secondary gaps and ring-structures, created by spiral arms, which were emitted from the growing Jupiter and/or Saturn. The distinct isotopic compositions of these reservoirs may reflect thermal processing of material within the disk in combination with temporal isotopic variations either due to isotopically variable infalling material from a heterogeneous molecular cloud and/or thermal processing during the infall that induced such heterogeneities. Such effects were likely reinforced by thermal processing of the material within the disk itself and by physical size- and density sorting of dust caused by the giant planets, creating gaps and pressure bumps in the disk.

Genetic relationships of meteorite groups and their implications on parent body formation are evaluated. New high precision Ti isotope data are consistent with that (i) CH and CB meteorites derive from a common parent body, which most likely accreted material from the same isotopic reservoir as the parent body of CR chondrites, (ii) silicates of IAB irons and winonaites originate from the same parent body, and (iii) mesosiderites and HED meteorites have a common origin on Vesta. The indistinguishable Ti and Cr isotope compositions of HEDs/mesosiderites to acapulcoites are not attributed to a common parent body, because of petrologic and chemical differences in addition to their distinct O isotope compositions. Their parent bodies likely accreted in the same disk region, which showed a higher level of O isotope heterogeneity compared to that of Ti, Cr and other refractory nucleosynthetic tracers. The similarity in Ti isotope compositions of Martian meteorites and OCs indicates that OC-like material belongs to the main building blocks of Mars.