Meteoritics & Planetary Science最新文献

{"title":"Cover","authors":"","doi":"10.1111/maps.14197","DOIUrl":"https://doi.org/10.1111/maps.14197","url":null,"abstract":"<p>\u0000 \u0000 <figure>\u0000 <div><picture>\u0000 <source></source></picture><p></p>\u0000 </div>\u0000 </figure>\u0000 </p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"i"},"PeriodicalIF":2.2,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14197","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CM carbonaceous chondrite petrofabrics and their implications for understanding the relative chronologies of parent body deformation and aqueous alteration","authors":"C. J. Floyd,&nbsp;L. E. Jenkins,&nbsp;P.-E. Martin,&nbsp;L. Daly,&nbsp;M. R. Lee","doi":"10.1111/maps.14303","DOIUrl":"https://doi.org/10.1111/maps.14303","url":null,"abstract":"<p>CM chondrites have been subjected to numerous alteration processes including brecciation and ductile deformation. Here, we present the results of 2D and 3D petrofabric analysis across a suite of meteorites: Aguas Zarcas, Cold Bokkeveld, Lewis Cliff (LEW) 85311, Murchison, and Winchcombe. We find that chondrule-defined petrofabrics are commonplace, but not ubiquitous. Where petrofabrics are present, alignment is typically observed in the chondrule long axes defining foliation fabrics. Alongside previous authors we interpolate the shock pressures to generate such fabrics between 27.8 and 41.8 GPa. Impacts capable of generating these shock pressures should ordinarily produce shock microstructures in olivine something not observed in the CMs. Whilst high calculated pre-compaction porosities may have had a role in attenuating energy transfer during collisions, we suggest the assumption of chondrule sphericity used in these calculations is misplaced and that a non-spherical pre-deformation chondrule shape is likely responsible for the dichotomy. We also reveal that the relative timings of aqueous alteration, brecciation, and deformation vary between CMs. Within Aguas Zarcas, we find multiple lithic clasts interpreted as having experienced different degrees of aqueous alteration, with opposing fabrics that formed after water/rock interaction but prior to brecciation. Meanwhile, within Cold Bokkeveld, we find a consistent fabric between clasts suggesting the fabric was imposed after both aqueous alteration and brecciation.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"324-346"},"PeriodicalIF":2.2,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14303","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143424125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic meteorite collection in the Catalina Dense Collection area (Chile): Description and statistics","authors":"Carine Sadaka,&nbsp;Jérôme Gattacceca,&nbsp;Matthieu Gounelle,&nbsp;Mathieu Roskosz,&nbsp;Anthony Lagain,&nbsp;Romain Tartese,&nbsp;Lydie Bonal,&nbsp;Clara Maurel,&nbsp;Rodrigo Martinez,&nbsp;Millarca Valenzuela","doi":"10.1111/maps.14307","DOIUrl":"https://doi.org/10.1111/maps.14307","url":null,"abstract":"<p>We present the outcome of search campaigns conducted in the Catalina Dense Collection area (DCA) located in the central depression of the Atacama Desert, Chile. The “Catalina Systematic Collection” (CSC) was assembled through systematic on-foot searches, resulting in a total of 1599 meteorites, before pairing, collected over a surface of 6.80 km². This yielded a recovery density of 235 meteorites per km² (67 meteorites &gt;20 g per km²), making it the densest among hot deserts, even higher than the neighboring El Médano DCA collection. This confirms that the central depression of the Atacama Desert holds the highest meteorite density among hot deserts. We classified 457 meteorites weighing more than 20 g. After correcting for various recovery biases, we estimated a true meteorite density on the ground of 131 meteorites per km² for meteorites &gt;20 g before pairing. Using a probabilistic approach, we calculated an average pairing likelihood, yielding 71 meteorites &gt;20 g per km² after pairing. This high density is likely linked to an old age of the CSC, which would also explain the absence of carbonaceous chondrites, as they are more prone to alteration by abrasion. This long meteorite accumulation period is related to the long-term hyper-aridity and surface stability of the Atacama Desert, which have persisted for several million years. Meteorites from the CSC show less chemical weathering on average than in other hot deserts, despite the long accumulation period. The H/L ratio in the CSC is higher than in meteorites from other hot deserts, Antarctica, and falls, but similar to the El Médano collection, potentially reflecting variations in the composition of the meteorite flux over the past Myr.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"308-323"},"PeriodicalIF":2.2,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14307","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cover","authors":"","doi":"10.1111/maps.14195","DOIUrl":"https://doi.org/10.1111/maps.14195","url":null,"abstract":"<p>\u0000 \u0000 <figure>\u0000 <div><picture>\u0000 <source></source></picture><p></p>\u0000 </div>\u0000 </figure>\u0000 </p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 1","pages":"i"},"PeriodicalIF":2.2,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14195","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143114005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrology and shock history of hybrid lunar feldspathic–troctolitic breccia Northwest Africa 11515","authors":"Y. Li,&nbsp;P. J. A. McCausland,&nbsp;R. L. Flemming,&nbsp;G. R. Osinski","doi":"10.1111/maps.14301","DOIUrl":"https://doi.org/10.1111/maps.14301","url":null,"abstract":"<p>Lunar impact breccia meteorites contain clasts from unknown lunar regions, including areas not studied by past missions. These meteorites offer a unique opportunity to expand our knowledge of the Moon's crustal and mantle composition and processes. The recently classified lunar meteorite Northwest Africa (NWA) 11515 is a moderately shocked feldspathic breccia with anorthite plagioclase and mafic minerals. In this work, we report the shock history of lithic clasts using 2-D micro-X-ray diffraction, detailed mineralogy from micro-X-ray fluorescence, and electron probe microanalysis. NWA 11515 shows moderately shocked anorthite and highly shocked olivine and pyroxene. The plagioclase composition is invariant (An96.4 ± 0.7, <i>n</i> = 52), with variable mafic clasts overlapping Mg- and FAN-suite lithologies (Mg# 84.5 to 45.6 for olivine; Mg# 85.6 to 32.2 for pyroxene), similar to KREEP-depleted troctolites in Allan Hills A81005. Spinel-group oxides vary from aluminous spinel to chromite and ulvöspinel. We also observed slow-cooled augite Ca-poor pyroxene exsolution clasts and fast-quenched fine-grained anorthite–olivine co-crystallized clasts (&lt;5 μm), indicating different cooling histories. Combining petrological observations with published geochemical data, we show NWA 11515 has the mixed lithology of ferroan anorthosites with KREEP-poor magnesian rock fragments. With shock analysis, the materials are likely from a crater with minimum size of 7 km. Finally, we examined the published geochemical data for other lunar meteorites and hypothesize that other typical feldspathic breccias could contain magnesian clasts, suggesting the subdivision of typical feldspathic breccia into magnesian clast-hosting breccia and ferroan feldspathic breccia. This implies that non-KREEP magnesian magmatism might be more widespread in the post-LMO era on lunar highlands.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"347-370"},"PeriodicalIF":2.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Search for pre-accretionary irradiation effects in calcium-aluminum inclusions from the CV3 chondrite Allende","authors":"P. Ghaznavi,&nbsp;C. Burkhardt,&nbsp;F. L. H. Tissot,&nbsp;I. Leya","doi":"10.1111/maps.14300","DOIUrl":"https://doi.org/10.1111/maps.14300","url":null,"abstract":"<p>Calcium-aluminum-rich inclusions (CAIs) are the first objects that formed in the solar accretion disk and therefore provide valuable insights into the evolution of the early solar system. A long-standing question regarding this earliest formative period relates to the storage of CAIs in the 1–4 Myr time period between their formation and later accretion into chondrite parent bodies. Were the CAIs stored in a pre-existing parent body, or in distant parts of the solar accretion disk? In the latter scenario, CAIs might have been exposed to cosmic rays, either from the galaxy or from the Sun and such pre-accretion irradiation effects might be detectable. We searched for such pre-accretional irradiation effects in 7 fine- and 11 coarse-grained CAIs from the CV 3.6 carbonaceous chondrite Allende. The extracted samples were analyzed for their major chemical composition and all samples were analyzed using μCT techniques. Using physical model calculations, ²¹Ne_cos and (²²Ne/²¹Ne)_cos production rate ratios were calculated for each CAI by fully considering their individual chemical composition. Measured He, Ne, Ar, and Kr isotope compositions of the CAIs show cosmogenic signals; clear signals for He and Ne isotopes; and detectable signals for some of the Ar and Kr isotopes. In addition, most samples show clear indications for radiogenic ⁴He and some samples show evidence for radiogenic ⁴⁰Ar. Higher ³⁶Ar/³⁸Ar, ²²Ne/²¹Ne, ⁸⁰Kr/⁸⁴Kr, and ⁸²Kr/⁸⁴Kr ratios together with lower cosmogenic ³⁸Ar_cos concentrations in fine-grained CAIs compared to coarse-grained CAIs are consistent with more alteration of the former compared to the latter. The CRE ages for the CAIs range between 4.12 ± 0.41 Myr and 6.40 ± 0.63 Myr. Statistical tests indicate that the data are normally distributed with no outliers, indicating that all CAIs share a common irradiation history, likely the irradiation in the Allende meteoroid. The average CRE age of 4.87 ± 0.19 Myr agrees with the nominally accepted CRE age of Allende of ~5.2 Myr. There is no correlation between ²¹Ne_cos concentrations and indicators of aqueous alteration like Na and/or U concentrations. The lack of correlation together with the finding of normally distributed modeled CRE ages indicates that either none of the studied CAIs experienced a pre-accretion irradiation before parent body compaction and/or that any pre-accretion irradiation effects have been completely erased during aqueous alteration events. Taking alteration aside, the findings are not in favor of X-wind type models but are more consistent with the idea of CAI outward transport in an expanding disk.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"247-272"},"PeriodicalIF":2.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14300","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geology, gravity, and numerical modeling of the Nova Colinas impact structure, Parnaíba Basin, Brazil","authors":"Pietro Demattê Avona,&nbsp;Alvaro Penteado Crósta,&nbsp;Marcos Alberto Rodrigues Vasconcelos,&nbsp;Evan Bjonnes,&nbsp;Fernando Lessa Pereira,&nbsp;Ana Maria Góes","doi":"10.1111/maps.14306","DOIUrl":"https://doi.org/10.1111/maps.14306","url":null,"abstract":"<p>Nova Colinas, centered at 07°09′33″ S/46°06′30″ W, is the ninth confirmed complex impact structure in Brazil and the fifth in the Parnaíba Basin, with a diameter of ~6.5–7 km and a nearly circular shape. Impactites include shocked siltstones from the Pedra de Fogo Fm. found at the central peak, brecciated sandstone from the Sambaíba Fm. bearing microscopic shock features, and brecciated basalt from the Mosquito Fm. bearing shatter cones. The impact event's age has been constrained to the interval from ~130 to ~199 Ma based on the local stratigraphy. Due to its moderate to advanced stage of erosion, geophysical modeling combined with geological field data were employed for its characterization. A new geological map was produced through field observations and remote sensing image interpretation, as well as a 3-D model based on ground gravity data and numerical modeling. iSALE2D shock physics code was employed to simulate the formation of Nova Colinas crater. The results revealed its main structural zones: the central uplift, annular basin, and outer rim, each associated with specific lithostratigraphic units from the Parnaíba Basin. Bouguer residual anomalies ranged from −3.6 to 1.2 mGal, with a nearly circular positive anomaly at the center of the structure, surrounded by a negative anomaly. 3-D gravity data inversion indicated a buried high-density body, likely due to the uplift of a diabase sill. Results of the numerical modeling point out that the final crater reached gravitational stability with a diameter of ~7 km and a depth of ~240 m, suggesting that a narrow outcrop strip of the Motuca Fm. was uplifted to a higher level compared to the Sambaíba Fm. strata, forming an antiform-like “arch” that creates an inner ring that exposes rocks of the Motuca Formation.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"286-307"},"PeriodicalIF":2.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrologic characterization of CO3.0 chondrites: Implications for 60Fe-60Ni analyses","authors":"Myriam Telus,&nbsp;Tyler D. Wickland,&nbsp;Kyle Kim,&nbsp;Steven Simon","doi":"10.1111/maps.14299","DOIUrl":"https://doi.org/10.1111/maps.14299","url":null,"abstract":"<p>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 <i>in situ</i> 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.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"225-246"},"PeriodicalIF":2.2,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14299","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143424020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methylene-to-methyl ratio variability in Ryugu samples: Clues to a heterogeneous aqueous alteration","authors":"Zélia Dionnet,&nbsp;Zahia Djouadi,&nbsp;Lukas Delaye,&nbsp;Lucas Caron,&nbsp;Rosario Brunetto,&nbsp;Alice Aléon-Toppani,&nbsp;Cateline Lantz,&nbsp;Stefano Rubino,&nbsp;Donia Baklouti,&nbsp;Tomoki Nakamura,&nbsp;Ferenc Borondics,&nbsp;Christophe Sandt,&nbsp;Megumi Matsumoto,&nbsp;Kana Amano,&nbsp;Tomoyo Morita,&nbsp;Hisayoshi Yurimoto,&nbsp;Takaaki Noguchi,&nbsp;Ryuji Okazaki,&nbsp;Hikaru Yabuta,&nbsp;Hiroshi Naraoka,&nbsp;Kanako Sakamoto,&nbsp;Shogo Tachibana,&nbsp;Toru Yada,&nbsp;Masahiro Nishimura,&nbsp;Aiko Nakato,&nbsp;Akiko Miyazaki,&nbsp;Kasumi Yogata,&nbsp;Masanao Abe,&nbsp;Tatsuaki Okada,&nbsp;Tomohiro Usui,&nbsp;Makoto Yoshikawa,&nbsp;Takanao Saiki,&nbsp;Satoshi Tanaka,&nbsp;Fuyuto Terui,&nbsp;Satoru Nakazawa,&nbsp;Seiichiro Watanabe,&nbsp;Yuichi Tsuda,&nbsp;the Hayabusa2-initial-analysis Stone team","doi":"10.1111/maps.14304","DOIUrl":"https://doi.org/10.1111/maps.14304","url":null,"abstract":"<p>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.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"273-285"},"PeriodicalIF":2.2,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143424253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cafeosite, Ca4Fe2+3Fe3+2□O6S4, a new meteoritic oxysulfide, a redox indicator of metamorphic alteration of carbonaceous asteroids","authors":"Marina A. Ivanova,&nbsp;Sergey N. Britvin,&nbsp;Roza I. Gulyaeva,&nbsp;Sofia A. Petrova,&nbsp;Nina G. Zinovieva,&nbsp;Vladimir V. Kozlov,&nbsp;Stanislav N. Tyushnyakov,&nbsp;Anatoly V. Kasatkin","doi":"10.1111/maps.14296","DOIUrl":"https://doi.org/10.1111/maps.14296","url":null,"abstract":"&lt;p&gt;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: Fe&lt;sup&gt;3+&lt;/sup&gt;, Fe&lt;sup&gt;2+&lt;/sup&gt;, and intermediate between Fe&lt;sup&gt;2+&lt;/sup&gt; and Fe&lt;sup&gt;0&lt;/sup&gt; involved in metallic-type Fe&lt;span&gt;&lt;/span&gt;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)&lt;sup&gt;−&lt;/sup&gt;, H&lt;sub&gt;2&lt;/sub&gt;O or CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2−&lt;/sup&gt; 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 &lt;i&gt;Cmce&lt;/i&gt; (#64), &lt;i&gt;a&lt;/i&gt; 17.4856(9), &lt;i&gt;b&lt;/i&gt; 11.1516(5), &lt;i&gt;c&lt;/i&gt; 11.1543(5) Å, &lt;i&gt;V&lt;/i&gt; 2175.0(2) Å&lt;sup&gt;3&lt;/sup&gt;, &lt;i&gt;Z&lt;/i&gt; = 8, &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;x&lt;/sub&gt; = 4.11 g cm&lt;sup&gt;−3&lt;/sup&gt;. The crystal structure has been solved and refined to &lt;i&gt;R&lt;/i&gt;&lt;sub&gt;1&lt;/sub&gt; = 0.039 for 1105 unique reflections. Chemical composition of both natural and synthetic cafeosite corresponds to the formula Ca&lt;sub&gt;4&lt;/sub&gt;Fe&lt;sup&gt;2+&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;Fe&lt;sup&gt;3+&lt;/sup&gt;&lt;sub&gt;2&lt;/sub&gt;(□&lt;sub&gt;1−x&lt;/sub&gt;Fe&lt;sub&gt;x&lt;/sub&gt;)O&lt;sub&gt;6&lt;/sub&gt;S&lt;sub&gt;4&lt;/sub&gt; where (□&lt;sub&gt;1−&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Fe&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;) denotes structural vacancy partially occupied by semimetallic-type Fe (&lt;i&gt;x&lt;/i&gt; = 0.2–0.3). The ideal endmember formula of the mineral is Ca&lt;sub&gt;4&lt;/sub&gt;Fe&lt;sup&gt;2+&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;Fe&lt;sup&gt;3+&lt;/sup&gt;&lt;sub&gt;2&lt;/sub&gt;□O&lt;sub&gt;6&lt;/sub&gt;S&lt;sub&gt;4&lt;/sub&gt;. 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 Fe&lt;sup&gt;3+&lt;/sup&gt; and Fe&lt;sup&gt;2+&lt;/sup&gt;, 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–wüsti","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 2","pages":"175-189"},"PeriodicalIF":2.2,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143424254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}