Meteoritics & Planetary Science最新文献

{"title":"Differences in elemental abundances between CI chondrites and the solar photosphere","authors":"A. J. G. Jurewicz,&nbsp;A. M. Amarsi,&nbsp;D. S. Burnett,&nbsp;N. Grevesse","doi":"10.1111/maps.14272","DOIUrl":"https://doi.org/10.1111/maps.14272","url":null,"abstract":"<p>CI chondrites have been a proxy for the solar system since the mid-20th century. The photospheric and CI chondrite abundances (<b><i>P</i></b> and <b><i>CI</i></b>, respectively) show a strong correlation. <b><i>CI</i></b> as a proxy is also justified by the (i) smoothness of their abundances plotted as a function of odd mass number and (ii) agreement within the error of <b><i>P</i></b> as determined spectroscopically. But our statistical assessment of spectroscopic studies and solar wind from the Genesis mission indicates that the small, ~10%–30%, differences (residuals) between <b><i>CI</i></b> and <b><i>P</i></b> depend on the 50% condensation temperature (Tc₅₀). So, if <b><i>CI</i></b> is to be used as a proxy for <b><i>P</i></b>, Cosmochemists may want to add a correction to individual elements. Our work is consistent with two published hypotheses: that (i) residuals are linear with Tc₅₀ and (ii) that elements having Tc₅₀ &gt; 1343 K are depleted relative to those with 495 K &lt; Tc₅₀ &lt; 1343 K in <b><i>CI</i></b>. We discuss other interpretations which are also feasible. Understanding these small differences of the <b><i>CI</i></b> and <b><i>P</i></b> for different elements and their variation with Tc₅₀ can help constrain future models of solar system formation and the history of CI chondrites.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 12","pages":"3193-3214"},"PeriodicalIF":2.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14272","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142862024","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":"Ba and Sr isotopic patterns from step-leaching experiments on the pristine Aguas Zarcas CM2 meteorite","authors":"Liam S. T. McGovern,&nbsp;Bruce L. A. Charlier,&nbsp;Colin J. N. Wilson","doi":"10.1111/maps.14278","DOIUrl":"https://doi.org/10.1111/maps.14278","url":null,"abstract":"<p>Stepwise acid leaching experiments were performed on the pre-rain CM2 fall Aguas Zarcas to interrogate release patterns and isolate fractions with isotopic anomalies. Acid leachates and a bulk sample were analyzed for elemental abundances via solution ICP-MS, and Sr and Ba isotopic compositions were measured using TIMS. Isotopic systematics reveal diverse values for the bulk sample and leachates, interpreted to reflect the Aguas Zarcas parent body history. Compared with the NBS987 standard, μ⁸⁴Sr values for the bulk sample average + 90, while the leach fractions yield +326 to −2089, with the largest μ⁸⁴Sr depletions in the strongest acid leachates. For Ba isotopes, the bulk sample shows resolvable depletions (μ values) in ¹³⁰Ba (−210), ¹³⁵Ba (−64), ¹³⁷Ba (−73) and ¹³⁸Ba (−89). Early leachates show positive anomalies in ¹³⁰Ba (up to +2295), ¹³²Ba, ¹³⁵Ba, ¹³⁷Ba, and ¹³⁸Ba. In contrast, final leachates show strong depletions for the same nuclides (up to −60,000 ppm μ¹³⁰Ba). The Sr and Ba isotopic anomalies found in the earlier leachates suggest that nucleosynthetic signatures were redistributed to more soluble phases during parent body alteration. Moreover, contrasting <i>p</i>-nuclide Sr and Ba nucleosynthetic anomalies suggest that presolar contributions came from a variety of nucleosynthetic sources, including possibly a rotating massive star undergoing a core-collapse supernova or an electron capture supernova.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 12","pages":"3353-3369"},"PeriodicalIF":2.2,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142861727","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":"Constraints on the impact history of the Apollo 16 landing site: Implications of soil-like breccia noble gas records","authors":"M. C. Nottingham,&nbsp;N. M. Curran,&nbsp;J. Pernet-Fisher,&nbsp;R. Burgess,&nbsp;I. A. Crawford,&nbsp;J. D. Gilmour,&nbsp;R. Tartèse,&nbsp;K. H. Joy","doi":"10.1111/maps.14244","DOIUrl":"https://doi.org/10.1111/maps.14244","url":null,"abstract":"<p>The Apollo 16 regolith breccia sample suite provides a record of lunar regolith formation from the basin-forming epoch (~3.9 Ga) through to a time of declining impactor flux (~2 Ga). These rocks have been characterized into three groups: the “ancient,” “young,” and “soil-like” regolith breccias on the basis of their petrographic characteristics, and, in the case of the “ancient” and “young” regolith breccias, noble gas inventory. This study investigates the as-yet unexamined noble gas records of the “soil-like” regolith breccias to understand more recent regolith evolution processes that occurred at the Apollo 16 landing site. The range of gas concentrations measured for each noble gas in these samples is comparable to those previously reported for the local Apollo 16 soils. The “soil-like” regolith breccias were found to be more gas rich than the gas poor “young” and “ancient” regolith breccias, consistent with them having formed from comparatively mature soil(s). Our results further confirm the scientific value of lunar regolith breccias and bulk regolith samples as probes of the impact history and the space environment of the lunar surface across a wide range of time.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 11","pages":"2883-2921"},"PeriodicalIF":2.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14244","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642016","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.14020","DOIUrl":"https://doi.org/10.1111/maps.14020","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":"59 10","pages":"i"},"PeriodicalIF":2.2,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428956","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":"The secondary classification of unequilibrated chondrites","authors":"Emmanuel Jacquet,&nbsp;Béatrice Doisneau","doi":"10.1111/maps.14270","DOIUrl":"https://doi.org/10.1111/maps.14270","url":null,"abstract":"<p>The multiplication of decimal petrologic schemes for different or the same chondrite groups evinces a lack of unified guiding principle in the secondary classification of type 1–3 chondrites. We show that the current OC, R and CO classifications can be a posteriori unified, with only minor reclassifications, if the decimal part of the subtype is defined as the ratio <i>m</i> = Fa_I/Fa_II of the mean fayalite contents of type I and type II chondrules, rounded to the nearest tenth (with adaptations from Cr systematics for the lowest subtypes following the past literature). This parameter is more efficiently evaluable than the oft-used relative standard deviation of fayalite contents and defines a general metamorphic scale from M0.0 to M1, where the suffixed number is the rounded <i>m</i>. Type 3 chondrites thus span the range M0.0–M0.9 (i.e. subtypes 3.0–3.9) and M1 designates type 4. Corresponding applications are then proposed for other chondrite groups (with, e.g., CV secondary classification reduced to essentially three grades from M0.0 to M0.2, that is, subtypes 3.0–3.2). Known type 1 and 2 chondrites are at M0.0 (i.e. the metamorphic grade of type 3.0 chondrites), even so-called “CY” chondrites, since our metamorphic scale is insensitive to brief heating. Independently, we define an aqueous alteration scale from A0.0 to A1.0, where the suffixed number is the (rounded) phyllosilicate fraction (PSF). For CM and CR chondrites, the alteration degrees can be characterized in terms of the thin-section-based criteria of previous schemes which are thus incorporated in the present framework, if in a coarser, but hereby more robust form. We propose their corresponding petrologic subtype to be 3-<i>PSF</i>, rounded to the nearest tenth (so that type 1 would correspond to subtypes 2.0 and 2.1). Since nonzero alteration and metamorphic degrees remain mutually exclusive at the level of precision chosen, a single petrologic subtype ≈3+<i>m</i>-<i>PSF</i> indeed remains a good descriptor of secondary processes for all unequilibrated chondrites, obviating the explicit mention of our separate scales unless finer subdivisions are adopted for the most primitive chondrites.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 12","pages":"3150-3180"},"PeriodicalIF":2.2,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14270","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860488","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":"The Arpu Kuilpu meteorite: In-depth characterization of an H5 chondrite delivered from a Jupiter Family Comet orbit","authors":"Seamus L. Anderson,&nbsp;Gretchen K. Benedix,&nbsp;Belinda Godel,&nbsp;Romain M. L. Alosius,&nbsp;Daniela Krietsch,&nbsp;Henner Busemann,&nbsp;Colin Maden,&nbsp;Jon M. Friedrich,&nbsp;Lara R. McMonigal,&nbsp;Kees C. Welten,&nbsp;Marc W. Caffee,&nbsp;Robert J. Macke,&nbsp;Seán Cadogan,&nbsp;Dominic H. Ryan,&nbsp;Fred Jourdan,&nbsp;Celia Mayers,&nbsp;Matthias Laubenstein,&nbsp;Richard C. Greenwood,&nbsp;Malcom P. Roberts,&nbsp;Hadrien A. R. Devillepoix,&nbsp;Eleanor K. Sansom,&nbsp;Martin C. Towner,&nbsp;Martin Cupák,&nbsp;Philip A. Bland,&nbsp;Lucy V. Forman,&nbsp;John H. Fairweather,&nbsp;Ashley F. Rogers,&nbsp;Nicholas E. Timms","doi":"10.1111/maps.14268","DOIUrl":"https://doi.org/10.1111/maps.14268","url":null,"abstract":"<p>Over the Nullarbor Plain in South Australia, the Desert Fireball Network detected a fireball on the night of June 1, 2019 (7:30 pm local time), and 6 weeks later recovered a single meteorite (42 g) named Arpu Kuilpu. This meteorite was then distributed to a consortium of collaborating institutions to be measured and analyzed by a number of methodologies including SEM-EDS, EPMA, ICP-MS, gamma-ray spectrometry, ideal gas pycnometry, magnetic susceptibility measurement, μCT, optical microscopy, and accelerator and noble gas mass spectrometry techniques. These analyses revealed that Arpu Kuilpu is an unbrecciated H5 ordinary chondrite, with minimal weathering (W0-1) and minimal shock (S2). The olivine and pyroxene mineral compositions (in mole%) are Fa: 19.2 ± 0.2 and Fs: 16.8 ± 0.2, further supporting the H5 type and class. The measured oxygen isotopes are also consistent with an H chondrite (δ¹⁷O‰ = 2.904 ± 0.177; δ¹⁸O‰ = 4.163 ± 0.336; Δ¹⁷O‰ = 0.740 ± 0.002). Ideal gas pycnometry measured bulk and grain densities of 3.66 ± 0.02 and 3.77 ± 0.02 g cm⁻³, respectively, yielding a porosity of 3.0% ± 0.7. The magnetic susceptibility of this meteorite is log <i>χ</i> = 5.16 ± 0.08. The most recent impact-related heating event experienced by Arpu Kuilpu was measured by ⁴⁰Ar/³⁹Ar chronology to be 4467 ± 16 Ma, while the cosmic ray exposure age is estimated to be between 6 and 8 Ma. The noble gas isotopes, radionuclides, and fireball observations all indicate that Arpu Kuilpu's meteoroid was quite small (maximum radius of 10 cm, though more likely between 1 and 5 cm). Although this meteorite is a rather ordinary ordinary chondrite, its prior orbit resembled that of a Jupiter Family Comet (JFC) further lending support to the assertion that many cm- to m-sized objects on JFC orbits are asteroidal rather than cometary in origin.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 11","pages":"3087-3110"},"PeriodicalIF":2.2,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642474","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":"Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu","authors":"Masaaki Miyahara,&nbsp;Takaaki Noguchi,&nbsp;Toru Matsumoto,&nbsp;Naotaka Tomioka,&nbsp;Akira Miyake,&nbsp;Yohei Igami,&nbsp;Yusuke Seto,&nbsp;Mitsutaka Haruta,&nbsp;Hikaru Saito,&nbsp;Satoshi Hata,&nbsp;Hope A. Ishii,&nbsp;John P. Bradley,&nbsp;Kenta K. Ohtaki,&nbsp;Elena Dobrică,&nbsp;Hugues Leroux,&nbsp;Corentin Le Guillou,&nbsp;Damien Jacob,&nbsp;Francisco de la Peña,&nbsp;Sylvain Laforet,&nbsp;Bahae-Eddine Mouloud,&nbsp;Maya Marinova,&nbsp;Falko Langenhorst,&nbsp;Dennis Harries,&nbsp;Pierre Beck,&nbsp;Thi H. V. Phan,&nbsp;Rolando Rebois,&nbsp;Neyda M. Abreu,&nbsp;Jennifer Gray,&nbsp;Thomas Zega,&nbsp;Pierre-M. Zanetta,&nbsp;Michelle S. Thompson,&nbsp;Rhonda Stroud,&nbsp;Kate Burgess,&nbsp;Brittany A. Cymes,&nbsp;John C. Bridges,&nbsp;Leon Hicks,&nbsp;Martin R. Lee,&nbsp;Luke Daly,&nbsp;Phil A. Bland,&nbsp;Michael E. Zolensky,&nbsp;David R. Frank,&nbsp;James Martinez,&nbsp;Akira Tsuchiyama,&nbsp;Masahiro Yasutake,&nbsp;Junya Matsuno,&nbsp;Shota Okumura,&nbsp;Itaru Mitsukawa,&nbsp;Kentaro Uesugi,&nbsp;Masayuki Uesugi,&nbsp;Akihisa Takeuchi,&nbsp;Mingqi Sun,&nbsp;Satomi Enju,&nbsp;Aki Takigawa,&nbsp;Tatsuhiro Michikami,&nbsp;Tomoki Nakamura,&nbsp;Megumi Matsumoto,&nbsp;Yusuke Nakauchi,&nbsp;Masanao Abe,&nbsp;Satoru Nakazawa,&nbsp;Tatsuaki Okada,&nbsp;Takanao Saiki,&nbsp;Satoshi Tanaka,&nbsp;Fuyuto Terui,&nbsp;Makoto Yoshikawa,&nbsp;Akiko Miyazaki,&nbsp;Aiko Nakato,&nbsp;Masahiro Nishimura,&nbsp;Tomohiro Usui,&nbsp;Toru Yada,&nbsp;Hisayoshi Yurimoto,&nbsp;Kazuhide Nagashima,&nbsp;Noriyuki Kawasaki,&nbsp;Naoya Sakamotoa,&nbsp;Ryuji Okazaki,&nbsp;Hikaru Yabuta,&nbsp;Hiroshi Naraoka,&nbsp;Kanako Sakamoto,&nbsp;Shogo Tachibana,&nbsp;Sei-ichiro Watanabe,&nbsp;Yuichi Tsuda","doi":"10.1111/maps.14271","DOIUrl":"https://doi.org/10.1111/maps.14271","url":null,"abstract":"<p>The surface morphology of regolith grains from the C-type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105-042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine-grained Mg-Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg-Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro-fault, the shock pressure recorded in the C0105-042 Ryugu grain is estimated to be &lt;~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105-042, together with those of C0014 (~2 GPa) and C0055 (&gt;~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are &lt; ~0.89–1.63 km s⁻¹. Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 12","pages":"3181-3192"},"PeriodicalIF":2.2,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142862095","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":"Effects of hot desert weathering on highly siderophile elements in ordinary chondrites","authors":"Kiran Shahood Almas,&nbsp;Richard D. Ash,&nbsp;Richard J. Walker","doi":"10.1111/maps.14267","DOIUrl":"https://doi.org/10.1111/maps.14267","url":null,"abstract":"<p>Over 20,000 meteorites have been recovered from hot deserts. The effects of hot desert weathering upon highly siderophile elements (HSE) have been little studied. We have investigated the effects of neutral to mildly acidic leaching of three L6-type ordinary chondrites of different weathering grades on HSE concentrations and Re-Os isotopic systematics. We have characterized the bulk sample HSE patterns of these meteorites and conducted leaching experiments with progressively longer leaching times to determine the possible effects of long-term residence in a desert. The most weathered sample (NWA 14239) displayed greater HSE concentration homogeneity than the other samples and released lower quantities of HSEs during leaching. Water leaching was milder than acetic acid and did not significantly modify the Re-Os isotopic systematics of the residue relative to the bulk sample of NWA 869. Short-term leachates of the less weathered samples (Viñales and NWA 869) were characterized by low ¹⁸⁷Os/¹⁸⁸Os ratios, indicating the preferential dissolution of early solar system–formed phases such as non-magnetic chondrules and matrix with low Re/Os that are no longer intact in the most weathered sample. Of the HSE, Pd is most resistant to both water and acetic acid leaching, with a maximum removal of ~5% Pd, while Re, Os, and Ir are most mobile with up to 40% removal.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 11","pages":"3072-3086"},"PeriodicalIF":2.2,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14267","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642430","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":"Fe, Zn, and Mg stable isotope systematics of acapulcoite lodranite clan meteorites","authors":"Stepan M. Chernonozhkin,&nbsp;Lidia Pittarello,&nbsp;Genevieve Hublet,&nbsp;Philippe Claeys,&nbsp;Vinciane Debaille,&nbsp;Frank Vanhaecke,&nbsp;Steven Goderis","doi":"10.1111/maps.14258","DOIUrl":"https://doi.org/10.1111/maps.14258","url":null,"abstract":"<p>The processes of planetary accretion and differentiation, whereby an unsorted mass of primitive solar system material evolves into a body composed of a silicate mantle and metallic core, remain poorly understood. Mass-dependent variations of the isotope ratios of non-traditional stable isotope systems in meteorites are known to record events in the nebula and planetary evolution processes. Partial melting and melt separation, evaporation and condensation, diffusion, and thermal equilibration between minerals at the parent body (PB) scale can be recorded in the isotopic signatures of meteorites. In this context, the acapulcoite–lodranite meteorite clan (ALC), which represents the products of thermal metamorphism and low-degree partial melting of a primitive asteroid, is an attractive target to study the processes of early planetary differentiation. Here, we present a comprehensive data set of mass-dependent Fe, Zn, and Mg isotope ratio variations in bulk ALC species, their separated silicate and metal phases, and in handpicked mineral fractions. These non-traditional stable isotope ratios are governed by mass-dependent isotope fractionation and provide a state-of-the-art perspective on the evolution of the ALC PB, which is complementary to interpretations based on the petrology, trace element composition, and isotope geochemistry of the ALC. None of the isotopic signatures of ALC species show convincing co-variation with the oxygen isotope ratios, which are considered to record nebular processes occurring prior to the PB formation. Iron isotopic compositions of ALC metal and silicate phases broadly fall on the isotherms within the temperature ranges predicted by pyroxene thermometry. The isotope ratios of Mg in ALC meteorites and their silicate minerals are within the range of chondritic meteorites, with only accessory spinel group minerals having significantly different compositions. Overall, the Mg and Fe isotopic signatures of the ALC species analyzed are in line with their formation as products of high-degree thermal metamorphism and low-degree partial melting of primitive precursors. The δ^66/64Zn values of the ALC meteorites demonstrate a range of ~3.5‰ and the Zn is overall isotopically heavier than in chondrites. The superchondritic Zn isotopic signatures have possibly resulted from evaporative Zn losses, as observed for other meteorite parent bodies. This is unlikely to be the result of PB differentiation processes, as the Zn isotope ratio data show no covariation with the proxies of partial melting, such as the mass fractions of the platinum group and rare earth elements.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 11","pages":"2956-2980"},"PeriodicalIF":2.2,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14258","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642361","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":"Finely layered CM2 carbonaceous chondrites may be analogs for layered boulders on asteroid (101955) Bennu","authors":"Erica R. Jawin,&nbsp;Timothy J. McCOY,&nbsp;Lisette E. Melendez,&nbsp;Catherine M. Corrigan,&nbsp;Kevin Righter,&nbsp;Harold C. Connolly Jr","doi":"10.1111/maps.14263","DOIUrl":"https://doi.org/10.1111/maps.14263","url":null,"abstract":"<p>Orbital observations of Bennu revealed a surface covered in boulders that are most similar among meteorites in our collections to aqueously altered carbonaceous chondrites, and initial analyses of the returned Bennu sample have begun to reveal insights into Bennu's origins. We identified a suite of paired CM2 chondrite meteorites that have a finely layered texture and bear a striking similarity, although at a different scale, to rugged, layered boulders on Bennu. We investigated the nature and potential origin of this layered texture by performing a petrofabric analysis on samples MET 00431, 00434, and 00435. We developed a micro-geospatial mapping framework that is more commonly used for landscape-scale investigations. Our results reveal a pervasive fracture network that exhibits a similar orientation to flattened particles dominated by tochilinite–cronstedtite intergrowths (TCI). We propose that their petrofabrics originated from a low-energy impact on the parent body that occurred after the main period of aqueous alteration halted. The impactdeformed TCI (which formed during earlier aqueous alteration) and generated the fractures. We propose that the sample from Bennu may contain particles with similar layered textures to these meteorites which, if present, would likewise indicate the dominant role of impacts and aqueous alteration on Bennu's parent body.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 11","pages":"3044-3055"},"PeriodicalIF":2.2,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642205","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}