¹Myriam Telus,^1,2Tyler D. Wickland,^1,3Kyle Kim,⁴Steven Simon
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14299]
¹Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California, USA
²Geological Sciences, University of Colorado Boulder, Boulder, Colorado, USA
³Department of Geology, University of Maryland College Park, College Park, Maryland, USA
⁴Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
Published by arrangement with John Wiley & Sons

Samples in which Fe and Ni isotopes have not been disturbed by secondary processing are essential for constraining the initial solar system abundance of short-lived radionuclide 60Fe, (60Fe/56Fe)SS. However, Fe- and Ni-enriched veins and fractures within chondrules in unequilibrated ordinary chondrites (UOCs) imply late-stage open-system alteration that poses a potential problem for both bulk and in situ 60Fe-60Ni systematics. This study focuses on petrologic characterization of CO3.0s, which show significantly less secondary alteration than UOCs, potentially making them better targets for studying 60Fe-60Ni systematics. We determined the petrologic type of several CO3.0 meteorites with two independent approaches, Raman spectroscopy of matrix material and Cr2O3 content of FeO-rich olivine grains. CO3 chondrites analyzed in this study range from 3.00 to 3.2 in petrologic type with slight variations between results from the two different methods. Upon analyzing two thin sections of DOM 08006, one of the most pristine CO3 chondrites known, we found a chemically anomalous region, indicative of parent body hydrothermal alteration. Using the X-ray fluorescence microscopy beamline at the Australian Synchrotron, we collected high-resolution quantitative element maps to evaluate Fe and Ni mobilization for several CO3.0s. These results indicate that late-stage Fe and Ni mobilization like that observed in UOC samples is minor for most CO3 chondrites, highly localized and mostly limited to chondrule rims. Our results support that CO3.0s are well suited for further investigation of 60Fe-60Ni systematics and that detailed characterization of both the petrologic type and late-stage Fe and Ni mobilization of samples is important for further development of this short-lived radionuclide system.

¹Chi Ma,²Oliver Tschauner,¹John R. Beckett,³Vitali B. Prakapenka
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14302]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²Department of Geoscience, University of Nevada, Las Vegas, Nevada, USA
³Center for Advanced Radiation Sources, The University of Chicago, Chicago, Illinois, USA
Published by arrangement with John Wiley & Sons

High-pressure oxides like perovskite-type FeTiO3, CaTi2O4-type Fe2TiO4, and ferrous-ferric oxides that form polysomes between wüstite and CaFe2O4-type Fe3O4 are potential carriers of Fe, Ti, and other transition metals in the mantle and may play an important role in the redox budget of the deep Earth. Here, we report the occurrence of three of these phases as the new minerals: feiite (Sr2Tl2O5-type Fe2+2(Fe2+Ti4+)O5), liuite (FeTiO3 with a GdFeO3-type perovskite structure), and tschaunerite (CaTi2O4-type (Fe2+)(Fe2+Ti4+)O4), along with wangdaodeite (LiNbO3-type FeTiO3) in a transformed ulvöspinel clast entrained in a shock melt pocket in the Shergotty Martian meteorite. We show that reaction between the shocked ulvöspinel precursor and melt occurred at pressures between 20 and 25 GPa. The high-pressure Fe-, Ti-minerals lost Fe and O to the surrounding shock melt in exchange for Si, Mg, and Ca. Concentrations of Si and Mg in all of these clast phases and of Na in liuite are significant. They substantiate chemical interaction of the clast with melt during the shock event and highlight potential elemental distributions in complex Fe- and Ti-rich lithologies at pressures of the deep transition zone to shallow lower mantle.

¹Marina A. Ivanova,^2,3Sergey N. Britvin,⁴Roza I. Gulyaeva,⁴Sofia A. Petrova,⁵Nina G. Zinovieva,⁶Vladimir V. Kozlov,⁴Stanislav N. Tyushnyakov,⁷Anatoly V. Kasatkin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14296]
¹Vernadsky Institute of Geochemistry of the Russian Academy of Sciences, Moscow, Russia
²Saint-Petersburg State University, St. Petersburg, Russia
³Kola Science Center, Russian Academy of Sciences, Apatity, Russia
⁴Institute of Metallurgy, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia
⁵Lomonosov Moscow State University, Moscow, Russia
⁶Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences, Petropavlovsk-Kamchatsky, Russia
⁷Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia
Published by arrangement with John Wiley & Sons

A natural iron-bearing oxysulfide, named сafeosite after its chemical composition, is a unique example of a mineral that simultaneously contains iron in three oxidation states: Fe3+, Fe2+, and intermediate between Fe2+ and Fe0 involved in metallic-type FeFe bonding. Cafeosite was discovered in metamorphosed carbonaceous chondrite Dhofar 225, which is classified as CM-anomalous but likely related to the CY (Yamato-type) group. The mineral occurs as tiny anhedral grains that coalesce into irregular aggregates up to 20 μm, commonly encrusted by micrometer-thick troilite or pyrrhotite rims. The grains are randomly disseminated within a chondrite matrix composed of thermally altered phyllosilicates. Associated accessory minerals are troilite, pyrrhotite, Fe-rich, Al-bearing olivine, unknown Al-bearing Fe sulfide, Al-rich chromite, kamacite, awaruite, pentlandite, escolaite, and perovskite. In reflected light, cafeosite is gray, with no internal reflections. Anisotropy is moderate, bireflectance in gray hues. Infrared microspectroscopy did not reveal any bands attributable to (OH)−, H2O or CO32− vibrations. Owing to the small grain size, the crystal structure of the mineral has been studied using synthetic analog, which was found to be isostructural with natural cafeosite based on electron backscatter diffraction (EBSD) data. Cafeosite is orthorhombic, space group Cmce (#64), a 17.4856(9), b 11.1516(5), c 11.1543(5) Å, V 2175.0(2) Å3, Z = 8, Dx = 4.11 g cm−3. The crystal structure has been solved and refined to R1 = 0.039 for 1105 unique reflections. Chemical composition of both natural and synthetic cafeosite corresponds to the formula Ca4Fe2+3Fe3+2(□1−xFex)O6S4 where (□1−xFex) denotes structural vacancy partially occupied by semimetallic-type Fe (x = 0.2–0.3). The ideal endmember formula of the mineral is Ca4Fe2+3Fe3+2□O6S4. Cafeosite was likely formed from previously altered precursor material of Dhofar 225, which, like common CM chondrites, consisted of phyllosilicates, Ca-bearing carbonates, tochilinite-like sulfides–hydroxides and pyrrhotite. During thermal metamorphism at temperatures between 750 and 900°C, sulfides–hydroxides were partly sintered with calcined carbonates and iron oxides, resulting in cafeosite formation. Due to varying and redox-dependent contents of Fe3+ and Fe2+, as well as the presence of metallic-type Fe in the structure, cafeosite could be regarded as a single-phase redox indicator alternative to the known triple-phase buffers, for example, iron–magnetite–pyrrhotite (IM-Po), iron–wüstite–pyrrhotite (IW-Po) and magnetite–wüstite–pyrrhotite (MW-Po) systems. Discovery of cafeosite provides insight into a previously obscured aspect of CY-chondrite formation: the redox conditions of thermal metamorphism on carbonaceous asteroids.

¹Zélia Dionnet et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14304]
¹CNRS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, Orsay, France
Published by arrangement with John Wiley & Sons

Understanding the processes of aqueous alteration within primitive bodies is crucial for unraveling the complex history of early planetesimals. To better identify the signs of this process and its consequences, we have studied the heterogeneity at a micrometric scale of the structure of the aliphatic organic compounds and its relationship to its mineralogical environment. Here, we report an analysis performed on two micrometric grains of Ryugu (C0002-FC027 and C0002-FC028). The samples were crushed in a diamond compression cell and analyzed using high-spatial resolution Fourier Transform InfraRed (FT-IR) hyperspectral imaging measurements conducted in transmission mode. We showed here the spatial distributions of the main components and the structural heterogeneity of the aliphatic organic matter highlighting a micrometer-scale variability in the methylene-to-methyl ratio. Moreover, we connected this heterogeneity to the one of the phyllosilicate band positions. Our findings indicate that the organic matter within Ryugu’s micrometric grains underwent varying degrees of aqueous alteration in distinct microenvironments resulting in an elongation of the length of their aliphatic chains, and/or a reduction in their branching and/or cross-linking.

^1,2L. Krämer Ruggiu,²B. Devouard,²J. Gattacceca,³L. Bonal,⁴L. Piani,⁵H. Leroux,⁶O. Grauby
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14295]
¹Archaeology, Environmental Changes and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
²CNRS, IRD, INRA, CEREGE, Aix Marseille Univ, Aix-en-Provence, France
³CNRS, IPAG, Univ. Grenoble Alpes, Grenoble, France
⁴CRPG, CNRS, Université de Lorraine, Vandoeuvre-les-Nancy, France
⁵CNRS, INRAE, Centrale Lille, UMR 8207 – UMET, Univ. Lille, Lille, France
⁶CNRS, CINaM, Aix-Marseille Université, Marseille, France
Published by arrangement with John Wiley & Sons

We studied Caleta el Cobre 022, a nakhlite showing a high abundance of aqueous alteration products, commonly called “iddingsite” and compared it to eight other nakhlites, in order to constrain the composition and the history of the aqueous alteration of nakhlites. Olivine grains in nakhlites display planes of secondary fluid inclusions, composed of pyroxene, magnetite, and a void potentially filled by a fluid. They were formed by a first fluid alteration event, previous to the iddingsite alteration event, probably from a late magmatic fluid circulation. We observed magnetite–pyroxene symplectites in olivine grains in most nakhlites, related to the same fluid-assisted tardi-magmatic event as the crystallization of the secondary inclusion planes. Those secondary inclusions and symplectites can be observed at the center of iddingsite veins, inside the most altered nakhlites, and are thus interpreted as being weakness planes, easing the circulation of the fluid forming the iddingsite inside the olivine grains. In every nakhlite, the alteration veins show at least two types of iddingsite: a coarse iddingsite with crystals around 50 nm, up to 200 nm, and a fine iddingsite with a nanocrystalline to amorphous texture with crystalline domains <10 nm. Both iddingsite types are composed mainly of Si, Mg, and Fe, with anticorrelated Si and Fe contents. The coarse iddingsite is composed of a mixture of phyllosilicates, with Fe-oxyhydroxides and minor siderite, and the fine iddingsite has a composition close to saponite. Organic matter located in coarse iddingsite is detected by Raman spectroscopy in the iddingsite of many nakhlites and was confirmed by the TEM study of NWA 10153. In addition, the TEM study of NWA 10153 displays complex chemical zoning in the fine iddingsite of Mg, Ca, Mn, S, P, and Al, suggesting at least two stages of circulations. Both the compositions and textures of the two types of iddingsite are suggestive of a progressive evolution of the alteration fluid, enriched in elements from basaltic mineral dissolution, with crystallization mainly by filling of existing fractures, and selective dissolution of host olivine. We also observe pyrrhotite–magnetite veinlets at the center of iddingsite veins and cross-cutting iddingsite veins and silicates, which are interpreted as the result of another later fluid circulation.

¹Daniel Sheikh,²Alex M. Ruzicka,³Melinda L. Hutson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14298]
Cascadia Meteorite Laboratory, Department of Geology, Portland State University, Portland, Oregon, USA
Published by arrangement with John Wiley & Sons

Pink spinel anorthosite (PSA), a distinctive plagioclase and spinel-rich lithology (spinel >20%) observed on the lunar surface by the Moon Mineralogy Mapper (M3) imaging spectrometer, has sparked considerable interest in understanding magmatic processes on the Moon that cannot be explained by the well-established lunar magma ocean paradigm. Competing ideas on the PSA-forming mechanisms have invoked either (1) impact melting of troctolitic source rocks on the lunar surface or (2) magma–wallrock interactions between anorthositic crust and Mg-suite parental melts, but have been difficult to evaluate given the lack of ground truth samples. Here, we investigate the textures and mineral compositions of seven PSA clasts in lunar meteorite Northwest Africa (NWA) 15500, and the bulk trace element compositions of a PSA clast separate and NWA 15500 host lithologies A and B. Our findings suggest derivation of PSA from an incompatible-element-poor source and are consistent with PSA representing an Mg-suite lithology genetically related to pink spinel troctolites that reflects increased degrees of crustal assimilation during magma–wallrock interactions, and a sourcing of PSA far from the Procellarum KREEP Terrane. Excavation of PSA material was followed by multiple, subsequent localized impact events, resulting in the formation of Lithologies A and B.

¹Glenn J. MacPherson, ²Michail I. Petaev
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.12.032]
¹Dept. of Mineral Sciences, U. S. National Museum of Natural History, Smithsonian Institution, Washington, D. C. 20560, United States
²Department of Earth & Planetary Sciences, Harvard University, 20 Oxford St., Hoffman 208, Cambridge, MA 02138, United States
Copyright Elsevier

New full equilibrium condensation calculations for a hot gas of solar composition show that anorthite condenses prior to forsterite at nebular pressures of 10⁻⁶, 10⁻⁵, 10⁻⁴, and 10⁻³ bars. Because of this difference relative to most previous condensation calculations, the predicted bulk composition trend for total condensed solids now more closely matches the trend defined by natural refractory inclusion bulk compositions. Especially this is true for Type B, Type C, and fine-grained spinel-rich inclusions. Some mismatch exists between our (and others’) calculations with respect to the MgO and SiO₂ compositions of natural inclusions. This is likely due to the kinetically-controlled condensation of spinel prior to melilite. We also explored the effects of pyroxene solid solution models and small degrees of fractional condensation, and found no significant effects on the condensation sequence. Although fractional condensation certainly occurred in the pre-solar nebula, our calculations require the degree of such fractionation to have been less than ∼1 %. Finally, although mass-dependent isotopic fractionation in Type B inclusions indicates some evaporative loss of magnesium and silicon during the molten stage of Type B inclusions, our results remove the necessity that such evaporation occurred in order to explain the bulk compositions of Type Bs. Nevertheless, our results are not incompatible with such evaporative loss.

¹Marina Martínez, ¹Adrian J. Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.12.020]
¹Department of Earth & Planetary Sciences, MSC03-2040, 1University of New Mexico, Albuquerque, NM 87131, USA
Copyright Elsevier

Phosphorus-bearing minerals in carbonaceous chondrites record early aqueous alteration effects in the parent asteroid and potentially provide clues on early solar nebular processes. Despite their importance, only a few studies exist dedicated to investigating P-bearing minerals in primitive carbonaceous chondrites and thus, their origins are not well constrained. Work on Ca phosphates around the edges of type IIA chondrules in primitive CR and CM chondrites has shown that Ca phosphates are generally associated with aqueous alteration in the parent body. The present study examines two different Ca phosphate occurrences in one of the least altered CR chondrites known, QUE 99177, by SEM, EPMA, and FIB-TEM techniques to better constrain their origins. The first type consists of elongate, submicron-sized rods of merrillite that occur in regions of mesostasis at the edge of type IIA chondrules adjacent to the surrounding matrix. The second type occurs as nanometer-sized grains around some type IA chondrules that are surrounded by smooth rims. These smooth rims are a type of rim that consists of an amorphous, Fe-rich, hydrous silicate phase that results from low-temperature aqueous alteration of silica in Silica-rich Igneous Rims (SIRs) at the earliest stages of parent body alteration. The Ca phosphates are located within discrete regions at the interface between smooth rims and adjacent matrix, ranging from whitlockite to apatite compositions. We argue that the first type of Ca phosphate has a solar nebular origin, formed by quenching of Ca- and P-bearing melts in chondrules at the final stages of crystallization, whereas the second type has a parent body origin, formed by oxidation of Fe,Ni metal grains in SIRs surrounding chondrules. Therefore, our new data and a reappraisal of previous data demonstrate, for the first time, that Ca phosphates formed by both primary (solar nebular) and secondary (parent body) processes. These results also provide additional insights into the formation conditions of type IIA chondrules in the protoplanetary disk and constrain the earliest stages of aqueous alteration in the CR chondrite parent body.

¹Samuel Ebert, ²Kazuhide Nagashima, ²Alexander N. Krot, ¹Addi Bischoff
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.12.025]
¹Institut für Planetologie, University of Münster, Münster, Germany
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

The nature of isotopic differences between ‘normal’ Ca,Al-rich inclusions (CAIs) characterized by the canonical initial 26Al/27Al ratio [(26Al/27Al)0] of ∼5 × 10−5 and the anomalous refractory inclusions characterized by the significantly lower (26Al/27Al)0, < ∼3 × 10−6, which include PLACs (platy hibonite crystals), PLAC-like inclusions, and some corundum-, hibonite-, and grossite-rich CAIs, remains controversial. The 26Al-poor inclusions may have formed earlier, prior to ‘normal’ CAIs, and recorded heterogeneous distribution of 26Al in the CAI-forming region, or they may have formed after nearly complete decay of 26Al, ∼ >4 Myr later than the canonical CAIs. Here we present the first high precision multi-isotopic (O, Mg, Ca, and Ti) study of refractory inclusions (RIs) in the EHa3 enstatite chondrite Sahara 97072 using in situ SIMS measurements. Our study revealed the presence of two isotopically distinct populations of CAIs in this meteorite: ‘normal’ CAIs and PLAC-like inclusions. The ‘normal’ CAIs composed of spinel, Al,Ti-diopside, ±hibonite, and secondary minerals, most likely replacing melilite, have solar-like Δ17O of ∼−23 ‰, ∼ the canonical (26Al/27Al)0, and no resolvable nucleosynthetic isotope anomalies in Ca and Ti. The PLAC-like inclusions composed of hibonite, corundum, and ± Al,Ti-pyroxene have Δ17O of ∼−19 ‰, no resolvable excess of radiogenic 26Mg, and large nucleosynthetic isotope anomalies in Ti and Ca: one inclusion has positive anomalies in 50Ti (835ε) and 48Ca (685ε), whereas another one has negative anomalies in 50Ti (−116ε), 46Ti (−112ε), 48Ca (−284ε).
We infer that (i) PLAC-like inclusions formed in an isotopically heterogeneous reservoir in which 48Ca and 50Ti were coupled but both isotopes were decoupled from 46Ti suggesting different carrier phases for 48Ca + 50Ti and 46Ti. (ii) ‘Normal’ CAIs formed in a reservoir with uniform distribution of Ca and Ti isotopes, possibly reflecting increasing homogenization of this region with time due to evaporation/condensation, mixing and aggregation of isotopically anomalous grains present in the protosolar molecular cloud. (iii) The observed differences in Δ17O of ‘normal’ and PLAC-like CAIs indicate their formation in nebular reservoirs with distinct O-isotope compositions, which could have resulted from evaporation of disk regions with different dust/gas ratios, assuming that dust and gas had different Δ17O values, possibly inherited from the protosolar molecular cloud. (iv) The 26Al-poor PLAC-like inclusions predate formation of ‘normal’ CAIs with the canonical (26Al/27Al)0 supporting heterogeneous distribution of 26Al in the CAI-forming region at the earliest stages of the protoplanetary disk evolution. This heterogeneity may have resulted from heterogeneous distribution of 26Al in the protosolar molecular cloud or from thermal processing of presolar grains having different abundances of live 26Al which were present in the molecular cloud with uniform distribution of 26Al/27Al ratio at the canonical level. We conclude that 26Al-26Mg systematics have a limited significance for the chronology of refractory inclusions.

¹Prajkta Mane, ¹Michael E. Zolensky
Nature Astronomy 8, 1508-1509 Link to Article [DOI https://doi.org/10.1038/s41550-024-02438-x]
¹Lunar and Planetary Institute, USRA, Houston, TX, USA
²NASA Johnson Space Center, Houston, TX, USA

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