Meteoritics & Planetary Science最新文献

{"title":"Iron XANES measurements of carbonates and phyllosilicates in CM chondrites: A record of redox conditions during aqueous alteration","authors":"Elizabeth Bailey,&nbsp;Myriam Telus,&nbsp;Phoebe J. Lam,&nbsp;Samuel M. Webb","doi":"10.1111/maps.70001","DOIUrl":"https://doi.org/10.1111/maps.70001","url":null,"abstract":"<p>Multiple generations of calcite and dolomite precipitated in CM chondrites during ice melting events that led to episodes of liquid water. Models and laboratory analysis have suggested a long-term transition from oxidizing to reducing conditions during aqueous alteration on the CM parent body. We found that synchrotron X-ray absorption near edge spectroscopy (XANES) can detect relative differences in the oxidation state of trace iron within these carbonates. In CM chondrites, previous work interpreted Mn abundance in calcite as an indicator of relatively early or late formation, and dolomite is understood to form relatively late. In the CM1 chondrite Meteorite Hills 01070, XANES maps reveal that Mn-poor calcite contains more oxidized iron relative to Mn-rich calcite. While these measurements of carbonates support increasing iron reduction with progressive aqueous alteration in MET 01070, comparison among different CM chondrites suggests a complex picture of redox evolution. In addition to carbonates, we performed XANES measurements of the phyllosilicate-rich matrix of Allan Hills 83,100. Pre-edge centroid analysis indicates that this CM1/2 has an oxidation state similar to typical CM2 chondrites. While additional measurements are warranted to confirm the full span of redox trends in CM carbonates, our data do not support a correlation between redox state and petrologic type.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"1953-1969"},"PeriodicalIF":2.4,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145100870","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":"Feasibility of in situ K-Ar isochron dating on Mars: Assessment using the mineralogy of Martian meteorites","authors":"Hikaru Hyuga,&nbsp;Yuichiro Cho,&nbsp;Yayoi N. Miura,&nbsp;Takashi Mikouchi,&nbsp;Seiji Sugita","doi":"10.1111/maps.70022","DOIUrl":"https://doi.org/10.1111/maps.70022","url":null,"abstract":"<p>Dating rocks with a 2<i>σ</i> precision of 200 Ma is required to understand the history of Martian habitability and volcanic activity since ~4000 Ma. In situ K-Ar dating using a spot-by-spot laser ablation technique has been developed for isochron dating on Mars. The precision of isochron ages is determined mainly by the relationship between the laser spot diameter and the grain size of the sample. However, the achievable precision of age estimates using a realistic mineralogy of Martian rocks has yet to be investigated. We simulated isochrons under various conditions, including different laser spot sizes, K and Ar measurement errors, and numbers of analyses based on the mineral abundances of representative Martian meteorites (NWA 817, Zagami, and NWA 1068) analyzed using an electron probe microanalyzer. We found that attaining a precision of 200 Ma necessitates an isochron data range, defined as the ratio of the maximum to minimum K concentrations, of &gt;6, a laser spot diameter of 250 μm, and measurement errors of &lt;10% for both K and Ar. Reducing the laser spot size and selecting a sample with a large grain size are effective in obtaining a large K range. Furthermore, minimizing the variance in measurement errors between K and Ar is essential to increase the accuracy of the age estimates. We demonstrate that the precision required for in situ dating on Mars is achievable with realistic instrument settings, thus demonstrating the feasibility of establishing an in situ K-Ar geochronology for Mars.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2076-2098"},"PeriodicalIF":2.4,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145100989","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":"Cosmic ray exposure ages and pre-atmospheric shielding of Omani meteorites: Implications for 14C and 14C/10Be terrestrial ages of meteorites from hot and cold deserts","authors":"Mohammad Tauseef,&nbsp;Ingo Leya,&nbsp;Beda Hofmann","doi":"10.1111/maps.70029","DOIUrl":"https://doi.org/10.1111/maps.70029","url":null,"abstract":"<p>We present isotope concentrations of the light noble gases He and Ne for samples from five well-documented strewnfields and two individual meteorites from the Omani desert. Cosmogenic (²²Ne/²¹Ne)_cos for the strewnfield samples are low, as expected considering the total known masses. A (²²Ne/²¹Ne)_cos of 1.210 for the LL6 chondrite RaS 267 from Oman indicates a small pre-atmospheric size of less than 10 cm. The CRE ages for the Omani meteorites calculated using ²¹Ne_cos range from 1 to 20 Ma. Using the (²²Ne/²¹Ne)_cos and previously established correlations, new shielding-corrected ¹⁴C and ¹⁴C-¹⁰Be terrestrial ages are calculated. For the strewnfield samples, the new ages are similar to the earlier ages but are more consistent. The new terrestrial age for RaS 267 is more than 20% lower than the previous age. Motivated by this success, we reinvestigated meteorites from other hot deserts (Acfer, Adrar, and Nullarbor regions) and Antarctica using literature data for ¹⁴C and (²²Ne/²¹Ne)_cos, along with the newly established correlations between ¹⁴C production rates and (²²Ne/²¹Ne)_cos. For these meteorites, the new terrestrial ages are systematically younger than the ages calculated earlier using a shielding-independent approach. Using shielding-corrected ¹⁴C terrestrial ages, the long-term puzzling problem that there is a lack of meteorites with short terrestrial ages disappears. The new histogram, though with only a limited number of data, shows the expected decrease in the number of meteorites with increasing terrestrial age. Therefore, the unexpected shape in the terrestrial age histogram was most likely due to a bias in the ¹⁴C dating system, that is, ages of small meteorites are overestimated.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2184-2196"},"PeriodicalIF":2.4,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70029","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101026","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":"Diaphite structures of Campo del Cielo cliftonites indicate a terrestrial collision-induced moderate shock process","authors":"Laura Noel García,&nbsp;Péter Némenth,&nbsp;Ronan Henry,&nbsp;Robert Luther,&nbsp;Maria Eugenia Varela","doi":"10.1111/maps.70024","DOIUrl":"https://doi.org/10.1111/maps.70024","url":null,"abstract":"<p>Cliftonites, polycrystalline aggregates of graphite with unusual cuboid morphology, are important carbon components of certain iron meteorites. Although they consist predominantly of sp²-bonded carbon, recent studies suggest that those from the Canyon Diablo (IAB) meteorite also include composite sp²- and sp³-bonded structures, named diaphites. Here, we investigate the nanostructure of cliftonites in a Campo del Cielo specimen and demonstrate that these cliftonites also contain a nanocomposite mixture of well-ordered 3R graphite regions interfingered with type 1 diaphite structure, consisting of &lt;01–10&gt; projected graphite and &lt;011&gt; projected diamond domains. This finding suggests that certain pieces of the Campo del Cielo meteorite experienced moderate shock pressures (&gt;~10 GPa), which exceed the 4–10 GPa pressure range previously reported for the main meteorite. We propose that a portion of Campo del Cielo cliftonites provides evidence for the shock-induced diamondization of graphite and the “projectile decapitation” process during terrestrial impact. The complexity of the initial carbonaceous material, combined with the wide range of pressures encountered during terrestrial impact events, may explain the diversity of nanostructures in the Campo del Cielo and Canyon Diablo cliftonites. Our findings could assist in the development of a pressure/shock classification system for characterizing impact events in graphite-bearing meteorites.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2114-2124"},"PeriodicalIF":2.4,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101043","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":"Matera: A not so ordinary H5 chondrite breccia with very low density and high porosity","authors":"Giovanni Pratesi,&nbsp;Tiberio Cuppone,&nbsp;Addi Bischoff,&nbsp;Markus Patzek,&nbsp;Philippe Schmitt-Kopplin,&nbsp;Matthias Laubenstein,&nbsp;Henner Busemann,&nbsp;Daniela Krietsch,&nbsp;Colin Maden,&nbsp;Richard Greenwood,&nbsp;Robert J. Macke,&nbsp;Xhonatan Shehaj,&nbsp;Dario Barghini,&nbsp;Albino Carbognani,&nbsp;Daniele Gardiol,&nbsp;PRISMA-Team","doi":"10.1111/maps.70025","DOIUrl":"https://doi.org/10.1111/maps.70025","url":null,"abstract":"<p>On the evening of February 14, 2023, at 17:58 UT, a fireball was detected by three cameras of the Italian PRISMA network (FRIPON network). The first samples of the Matera meteorite, collected 3 days after the fall, lay on the balcony of a private home. Meanwhile, four samples weighing more than 10 g (including the main mass of 46.21 g) and many minor samples (less than 10 g each) were recovered, with a total mass of 117.5 g. The analyses show that Matera is a monomict chondrite breccia, exhibiting no weathering (W0) and shock (S1). Based on the mineral compositions of olivine and low-Ca pyroxene (Fa_18.0±0.3 and Fs_17.0±0.3, respectively), the rock is an H-group ordinary chondrite. Since all low-Ca pyroxene is orthoenstatite, an H5-type classification is appropriate; although texturally, a type 4 classification could be assigned to distinct portions of the rock with well-defined chondrules. The analyzed oxygen isotopes also align with an H chondrite (δ¹⁷O‰ = 2.750 ± 0.051; δ¹⁸O‰ = 4.036 ± 0.103; Δ¹⁷O‰ = 0.650 ± 0.004). X-ray tomography and a structured light 3D scanner yielded a mean bulk density of 2.87 ± 0.04 g cm⁻³, whereas ideal gas pycnometry yielded grain densities of 3.47 ± 0.05 g cm⁻³, resulting in a porosity of 17.2 ± 1.2 vol%. The magnetic susceptibility of this meteorite is log <i>χ</i> = 5.46 ± 0.05. The radionuclides and fireball observations suggest that the Matera meteoroid was relatively small (with a maximum radius of 20 cm, though more likely around 15 cm). This datum is also consistent with (²¹Ne/²²Ne)_cos, which suggests the origin of Matera samples from the uppermost cm of a small meteoroid, ≤10 cm radius. Different from many other H chondrites, the transfer time in space for Matera, based on 3 He alone, is 10–12 Ma. Moreover, the Matera meteorite does not contain solar wind gases. In conclusion, the Matera meteorite is not a fairly typical ordinary chondrite, due to its low bulk density and high total porosity. The presence of ordinary chondrites with these physical characteristics must be taken into account during the asteroid modeling process, as in the case of the Didymos–Dimorphos binary system.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2125-2148"},"PeriodicalIF":2.4,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70025","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145100981","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":"Magnesium phosphate in the Cold Bokkeveld (CM2) carbonaceous chondrite","authors":"Martin R. Lee,&nbsp;Tobias Salge,&nbsp;Ian Maclaren","doi":"10.1111/maps.70018","DOIUrl":"https://doi.org/10.1111/maps.70018","url":null,"abstract":"<p>Hydrous Mg-phosphate was first described from astromaterials in particles returned from the C-type asteroid Ryugu, and has subsequently been found in samples of the B-type asteroid Bennu and CI1 carbonaceous chondrites. This phase may have been highly significant as a source of bioessential compounds for early Earth. Here, we describe Mg-phosphate from a petrologic type 1 clast (called “C1MP”) in the Cold Bokkeveld CM2 carbonaceous chondrite. This clast has a fine-grained serpentine–saponite matrix that in addition to the Mg-phosphate contains magnetite, Mg-Fe carbonate, calcite, pentlandite, transjordanite, eskolite, and daubréelite/zolenskyite. The Mg-phosphate grains are 7–36 μm in size and together constitute 0.27% of the clast by area. They have a “cracked” texture in scanning electron microscope images, and scanning transmission electron microscopy (STEM) shows that they are highly porous suggesting alteration of originally hydrous grains. The Mg-phosphate has Mg/P and Na/P ratios (atom%) of 1.02 and 0.25, respectively, along with minor concentrations of C, S, Cl, K, Ca, and Fe. Nitrogen was sought because ammonia has been reported from Ryugu Mg-phosphate, but none was detected by X-ray or electron spectroscopy. 4D-STEM shows that the C1MP clast's Mg-phosphate is amorphous, and radial distribution function analysis of electron diffraction patterns reveals that its P-O and Mg-P bonding distances are comparable to newberyite (MgHPO₄.3H₂O). The C1MP clast's Mg-phosphate formed from late-stage alkaline brines and subsequently underwent dehydration, amorphization, and partial loss of Na in response to heating in its parent body and/or during laboratory analysis.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2017-2032"},"PeriodicalIF":2.4,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145102391","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":"Amides from the carbonaceous asteroid (162173) Ryugu: Nanoscale spectral and isotopic characterizations","authors":"L. G. Vacher,&nbsp;V. T. H. Phan,&nbsp;L. Bonal,&nbsp;M. Iskakova,&nbsp;O. Poch,&nbsp;P. Beck,&nbsp;E. Quirico,&nbsp;R. C. Ogliore","doi":"10.1111/maps.70019","DOIUrl":"https://doi.org/10.1111/maps.70019","url":null,"abstract":"<p>C-type asteroids, such as asteroid (162173) Ryugu, may have played a key role in delivering light elements to early Earth. Nitrogen (N)-bearing molecules have been chemically identified in some Ryugu grains, and based on the faint 3.06 μm absorption band observed by the hyperspectral microscope MicrOmega, NH-bearing compounds seem to be spread at the global scale in the collection. However, the chemical forms of these NH-bearing compounds—whether organic molecules, ammonium (NH₄⁺) salts, NH₄⁺- or NH-organics-bearing phyllosilicates, or other forms—remain to be better understood. In this study, we report the characterization of two Ryugu particles (C0050 and C0052) using infrared spectroscopy at millimeter, micrometer, and nanometer scales, along with NanoSIMS techniques to constrain the nature and origin of NH-bearing components in the Ryugu asteroid. Our findings show that Ryugu's C0052 particle contains rare (~1 vol%), micrometer-sized NH-rich organic compounds with peaks at 1660 cm⁻¹ (mainly due to C=O stretching of the amide I band) and 1550 cm⁻¹ (mainly due to N-H bending vibration mode of the amide II band), indicative of amide-related compounds. In contrast, these compounds are absent in C0050. Notably, N isotopic analysis reveals that these amides in C0052 are depleted in ¹⁵N (<i>δ</i>¹⁵N ≃ −200‰), confirming their indigenous origin, while carbon (C) and hydrogen (H) isotopic compositions are indistinguishable from terrestrial values within errors. The amides detected in C0052 could have formed through hydrothermal alteration from carboxylic acids and amines precursors on Ryugu's parent planetesimal. Alternatively, they could have originated from the irradiation of ¹⁵N-depleted N-bearing ice by ultraviolet light or galactic cosmic rays, either at the surface of the asteroid in the outer Solar System or on the mantle of interstellar dust grains in the interstellar medium. Amides delivered to early Earth by primitive small bodies such as asteroid Ryugu may have contributed to the prebiotic chemistry.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2033-2051"},"PeriodicalIF":2.4,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145102308","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":"Ultrarefractory inclusions in the Sayh al Uhaymir 290 CH carbonaceous chondrite","authors":"Konstantin M. Ryazantsev,&nbsp;Marina A. Ivanova,&nbsp;Alexander N. Krot,&nbsp;Chi Ma,&nbsp;Cyril A. Lorenz,&nbsp;Vasily D. Shcherbakov","doi":"10.1111/maps.70020","DOIUrl":"https://doi.org/10.1111/maps.70020","url":null,"abstract":"<p>Ultrarefractory Ca,Al-rich inclusions (UR CAIs) in the Sayh al Uhaymir (SaU) 290 CH3 carbonaceous chondrite consist of ultrarefractory Zr,Sc-rich minerals (allendeite, kangite, tazheranite, warkite, and Y-perovskite), grossite, grossmanite, hibonite, melilite, and spinel. Several of them have a core–mantle structure with ultrarefractory minerals concentrated in the core. The unfragmented inclusions are surrounded by layers of spinel, melilite, Sc-diopside, and diopside (not all layers are present around individual inclusions). The UR CAIs have uniform ¹⁶O-rich compositions: Most inclusions have Δ¹⁷O of ~ −23 ± 2‰; a grossite-rich CAI is slightly ¹⁶O-depleted (Δ¹⁷O ~ −17‰). The CAIs are highly enriched in Zr, Hf, Sc, Y, and Ti compared to typical and previously studied UR CAIs from CM2, CO3, and CV3 carbonaceous chondrites. Similar to UR CAIs from other chondrites, the ultrarefractory minerals in SaU 290 CAIs are enriched in heavy rare earth elements (HREEs) relative to more volatile light rare earth elements (LREEs). We conclude that (1) UR CAIs from SaU 290 formed by gas–solid condensation from a gaseous reservoir having variable but mostly solar-like O-isotope composition, most likely near the proto-Sun, and were subsequently transported outward to the accretion region of CH chondrites. (2) The UR oxides and silicates are important carriers of UR REE patterns recorded their possible early fractionation.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 9","pages":"2052-2075"},"PeriodicalIF":2.4,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145102169","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":"Cover","authors":"","doi":"10.1111/maps.14207","DOIUrl":"https://doi.org/10.1111/maps.14207","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 7","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14207","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705488","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":"An atlas of apatite and merrillite in martian meteorites: REE Geochemistry and a new tool for shergottite classification","authors":"Tahnee Burke,&nbsp;Andrew G. Tomkins,&nbsp;Zsanett Pinter,&nbsp;Andrew D. Langendam,&nbsp;Laura A. Miller","doi":"10.1111/maps.70016","DOIUrl":"https://doi.org/10.1111/maps.70016","url":null,"abstract":"<p>The phosphates, apatite and merrillite, are accessory phases in all martian meteorites. Although apatite is commonly used to assess volatile content and speciation in martian meteorites, merrillite is at least twice as abundant in most samples, but poorly understood. Given that shergottites are divided into enriched, intermediate, and depleted subgroups based on bulk differences in light rare earth element (LREE) abundance and isotopic compositions, an understanding of phosphate mineral behavior is essential to deciphering the petrogenetic differences between these groups because they are the main REE-bearing phases. This study examines 10 enriched shergottites, six intermediate shergottites, and four depleted shergottites to investigate systematic variations in phosphate mineralogy and geochemistry. Two nakhlites, a chassignite, ALH 84001, and two pairs of NWA 7034 were also examined to cover all martian meteorite types known to date. Fourteen of the shergottites were previously classified into enriched, intermediate, and depleted subgroups based on bulk rock REE trends and La/Yb ratios. The remaining six shergottites had not been subgrouped during classification. All samples were elementally mapped using the XFM beamline at the Australian Synchrotron, which provided the relative abundance of merrillite, apatite, K-feldspar, and maskelynite within each sample (the same can be achieved with electron microprobe or SEM). We show that it is possible to classify shergottites from a single representative thin section using apatite to merrillite ratios (A¹⁰/M, where A¹⁰ is apatite abundance × 10) and K-feldspar to phosphate ratios (K¹⁰/P, where K¹⁰ is K-feldspar abundance × 10). Enriched shergottites typically have A¹⁰/M of 1.08 to 8.72 and K¹⁰/P of 1.85 to 13.34; intermediate shergottites have A¹⁰/M ranging from 0.5 to 0.96 and K¹⁰/P of 0.36 to 0.94; and depleted shergottites have A¹⁰/M ranging from 0.26 to 0.42 and K¹⁰/P of 0.09 to 0.39. Calculating these ratios thus provides a quick and straightforward method of chemically classifying shergottites that avoids the need to destroy samples for bulk rock REE analysis.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"60 8","pages":"1894-1920"},"PeriodicalIF":2.4,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905336","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}