Meteoritics & Planetary Science最新文献

{"title":"In Memoriam: Burkhard Dressler (1939–2024)","authors":"Wolfram Dressler, Wolf Uwe Reimold, Virgil L. (Buck) Sharpton, Christian Koeberl","doi":"10.1111/maps.14218","DOIUrl":"https://doi.org/10.1111/maps.14218","url":null,"abstract":"<p>Burkhard Bruno Otto Dressler passed away peacefully this April 2024 in Nanaimo (British Columbia, Canada), at the age of 84. His wife Bärbel Dressler was by his side, and his two sons, Wolfram and Andreas, sent him love from afar. Burkhard had been suffering for a decade from progressive medical problems that suddenly, in 2023, had accelerated.</p><p>Burkhard was the second of three siblings born to Hildegard and Gotthard Dressler of Schweidnitz, a town in Lower Silesia, formerly within Eastern Germany, now in Poland. He received his PhD in petrology, with a specialization in impact cratering studies, from the University of Munich/Technical University of Munich in 1970. He carried out extensive fieldwork, followed by detailed petrographic studies, for his PhD dissertation that was entitled “Petrology and shock attenuation, Manicouagan impact structure, Quebec, Canada.” In the following decades, Burkhard would emerge as a prominent figure in the study of impact structures in Ontario, Labrador, Quebec, the High Arctic of Canada, South Africa, and then in Mexico. How many impact workers can boast to have worked on all three of the largest impact structures on Earth? During his long and successful career, Burkhard Dressler published 56 refereed articles and chapters in monographs, with 26 of those having been dedicated to his impact studies.</p><p>Looking back in the early 2000s onto some 40 years of service to the Precambrian geology and impact cratering community, Burkhard described himself “as an experienced Precambrian field geologist and impact researcher.” His career-long interest in impact cratering and shock processes undoubtedly dates all the way back to his years as a graduate and postgraduate student in Munich, at a university located only 2 h from the Nördlinger Ries impact structure.</p><p>His career began around 1965 with shock petrographic studies of the igneous and metamorphic rocks of the Ries, and he proceeded to log the Wörnitzostheim drill core. From 1970 to 1975, Burkhard Dressler was employed as a staff geologist by the Geological Survey of the Quebec Ministère des Richesses Naturelles, working on the Proterozoic Labrador Fold Belt. By 1975, he, Bärbel, and two young children had relocated to southern Ontario, where he continued his career as a field geologist for the Ontario Geological Survey. He pursued mapping in the Southern, Superior, and Grenville provinces of Ontario. Between 1979 and 1981, he carried out his first investigations of the Sudbury structure and environs. This region includes two impact structures, the huge Sudbury structure and the only 7.5-km-diameter Wanapitei structure just a bit to the northeast. No in situ impactites were found exposed in the Wanapitei structure, but Burkhard studied the impact deformation in the country rocks around the lake and the impact glasses in suevitic breccia found in glacial deposits south of the lake. Faults and joints around the lake were identified to have a concentric p","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2565-2571"},"PeriodicalIF":2.2,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14218","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142169926","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 formation of volatile-bearing djerfisherite in reduced meteorites","authors":"Zoë E. Wilbur,&nbsp;Timothy J. McCoy,&nbsp;Catherine M. Corrigan,&nbsp;Jessica J. Barnes,&nbsp;Sierra V. Brown,&nbsp;Arya Udry","doi":"10.1111/maps.14220","DOIUrl":"10.1111/maps.14220","url":null,"abstract":"<p>Enstatite meteorites, both aubrites and enstatite chondrites, formed under exceptionally reducing conditions, similar to the planet Mercury. Despite being reduced, the MESSENGER mission showed that the surface of Mercury is more enriched in volatiles (e.g., S, Na, K, Cl) than previously thought. To better understand the mineral hosts of these volatiles and how they formed, this work examines the chemistry and petrographic settings of a rare, K-bearing sulfide called djerfisherite within enstatite chondrites and aubrites. The petrographic settings of djerfisherite within aubrites suggest this critical host of Cl formed after both the crystallization of troilite and exsolution of daubréelite. Djerfisherite is commonly observed as a rim on other sulfides and in contact with metal. We present an alteration model for djerfisherite formation in aubrite meteorites, whereby troilite and Fe-Ni metal are altered through anhydrous, alkali- and Cl-rich fluid metasomatism on the aubrite parent body to produce secondary djerfisherite. Moreover, we observe a loss of volatiles in djerfisherite within impact melted regions of the Miller Range 07139 EH3 chondrite and the Bishopville aubrite and explore the potential for impact devolatilization changes to sulfide chemistry on other reduced bodies in the Solar System. Vapor or fluid phase interactions are likely important in the formation of volatile-rich phases in reduced systems. While most Na and K on the mercurian surface is expected to be hosted in feldspar, djerfisherite is likely a minor, but critical, reservoir for K, Na, and Cl. Djerfisherite present on reduced bodies, such as Mercury, may represent sulfides formed via late-stage, primary metasomatism.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2373-2387"},"PeriodicalIF":2.2,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14220","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141269156","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":"Condensation of refractory minerals on igneous compact type A Ca-Al-rich inclusion from Northwest Africa 7865 CV chondrite","authors":"Akimasa Suzumura,&nbsp;Noriyuki Kawasaki,&nbsp;Hisayoshi Yurimoto,&nbsp;Shoichi Itoh","doi":"10.1111/maps.14222","DOIUrl":"10.1111/maps.14222","url":null,"abstract":"<p>A melilite-rich, compact type A Ca-Al-rich inclusion (CAI), KU-N-02, from the reduced CV3 chondrite Northwest Africa 7865, is mantled by an åkermanite-poor layer. We carried out a combined study of petrographic observations and in situ O and Al–Mg isotopic measurements for KU-N-02. The core shows a typical texture of igneous compact type A CAIs. The mantle consists of spinel, åkermanite-poor melilite, and perovskite. Individual mantle melilite crystals show reverse zoning toward the crystal grain boundary, in contrast to core melilite crystals showing normal zoning. The O isotopic compositions of the minerals in KU-N-02 plot along the carbonaceous chondrite anhydrous mineral line on a three O-isotope diagram. The mantle and core spinel crystals are uniformly ¹⁶O-rich (Δ¹⁷O ~ −23‰). The mantle melilite crystals exhibit variable O isotopic compositions ranging between Δ¹⁷O ~ −2‰ and −9‰, in contrast to the uniformly ¹⁶O-poor (Δ¹⁷O ~ −2‰) core melilite. The mantle melilite crystals also exhibit variable δ²⁵Mg values (δ²⁵Mg_DSM-3 ~ −2‰ to +3‰) compared with the nearly constant δ²⁵Mg values of the core melilite (δ²⁵Mg_DSM-3 ~ +2‰). The mantle minerals are likely to have formed by condensation from the solar nebular gas after core formation. The Al–Mg mineral isochrons of the core and mantle give initial ²⁶Al/²⁷Al ratios of (4.66 ± 0.15) × 10⁻⁵ and (4.74 ± 0.14) × 10⁻⁵, respectively. The age difference between the core and mantle formation is estimated to be within ~0.05 Myr, implying that both melting and condensation processes in the variable O isotopically solar nebular environments occurred within a short time during single CAI formation.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2388-2402"},"PeriodicalIF":2.2,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14222","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141270650","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 anomalous polymict ordinary chondrite breccia of Elmshorn (H3-6)—Late reaccretion after collision between two ordinary chondrite parent bodies, complete disruption, and mixing possibly about 2.8 Gyr ago","authors":"Addi Bischoff,&nbsp;Markus Patzek,&nbsp;Romain M. L. Alosius,&nbsp;Jean-Alix Barrat,&nbsp;Jasper Berndt,&nbsp;Henner Busemann,&nbsp;Detlev Degering,&nbsp;Tommaso Di Rocco,&nbsp;Mattias Ek,&nbsp;Jérôme Gattacceca,&nbsp;Jose R. A. Godinho,&nbsp;Dieter Heinlein,&nbsp;Daniela Krietsch,&nbsp;Colin Maden,&nbsp;Oscar Marchhart,&nbsp;Martin Martschini,&nbsp;Silke Merchel,&nbsp;Andreas Pack,&nbsp;Stefan Peters,&nbsp;Miriam Rüfenacht,&nbsp;Jochen Schlüter,&nbsp;Maria Schönbächler,&nbsp;Aleksandra Stojic,&nbsp;Jakob Storz,&nbsp;Wolfgang Tillmann,&nbsp;Alexander Wieser,&nbsp;Karl Wimmer,&nbsp;Reiner Zielke","doi":"10.1111/maps.14193","DOIUrl":"https://doi.org/10.1111/maps.14193","url":null,"abstract":"<p>Elmshorn fell April 25, 2023, about 30 km northwest of the city of Hamburg (Germany). Shortly after the fall, 21 pieces were recovered totaling a mass of 4277 g. Elmshorn is a polymict and anomalous H3-6 chondritic, fragmental breccia. The rock is a mixture of typical H chondrite lithologies and clasts of intermediate H/L (or L, based on magnetic properties) chondrite origin. In some of the 21 pieces, the H chondrite lithologies dominate, while in others the H/L (or L) chondrite components are prevalent. The H/L chondrite assignment of these components is based on the mean composition of their olivines in equilibrated type 4 fragments (~Fa_21–22). The physical properties like density (3.34 g cm⁻³) and magnetic susceptibility (log<i>χ</i> &lt;5.0, with <i>χ</i> in 10⁻⁹ m³ kg⁻¹) are typical for L chondrites, which is inconsistent with the oxygen isotope compositions: all eight O isotope analyses from two different fragments clearly fall into the H chondrite field. Thus, the fragments found in the strewn field vary in mineralogy, mineral chemistry, and physical properties but not in O isotope characteristics. The sample most intensively studied belongs to the stones dominated by H chondrite lithologies. The chemical composition and nucleosynthetic Cr and Ti isotope data are typical for ordinary chondrites. The noble gases in Elmshorn represent a mixture between cosmogenic, radiogenic, and primordially trapped noble gases, while a solar wind component can be excluded. Because the chondritic rock of Elmshorn contains (a) H chondrite parent body interior materials (of types 5 and 6), (b) chondrite parent body near-surface materials (of types 3 and 4), (c) fragments of an H/L chondrite (dominant in many stones), (d) shock-darkened fragments, and (e) clasts of various types of impact melts but no solar wind-implanted noble gases, the different components cannot have been part of a parent body regolith. The most straightforward explanation is that the fragmental breccia of Elmshorn represents a reaccreted rock after a catastrophic collision between an H chondrite parent body and another body with H/L (or L) chondrite characteristics but with deviating O isotope values (i.e. that of H chondrites), complete disruption of the bodies, mixing, and reassembly. This is the only straightforward way that the implantation of solar wind gases could have been avoided in this kind of complex breccia. The gas retention ages of about 2.8 Gyr possibly indicate the closure time after the catastrophic collision between H and H/L (or L) chondrite parent bodies, while the cosmic ray exposure age for Elmshorn, which had a preatmospheric radius of 25–40 cm, is ~17–20 Myr.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2321-2356"},"PeriodicalIF":2.2,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14193","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142170365","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 Aguas Zarcas carbonaceous chondrite meteorite: Brecciation and aqueous alteration on the parent body","authors":"I. Kouvatsis,&nbsp;J. A. Cartwright,&nbsp;W. E. Hames","doi":"10.1111/maps.14219","DOIUrl":"https://doi.org/10.1111/maps.14219","url":null,"abstract":"<p>CM chondrites are samples from primitive water-rich asteroids that formed early in the solar system; many record evidence for silicate rock–liquid water interaction. Many CM chondrites also exhibit well-developed fine-grained rims (FGRs) that surround major components, including chondrules and refractory inclusions. Previous studies have shown that Aguas Zarcas, a CM2 chondrite fall recovered in 2019, is a breccia consisting of several lithologies. Here, we present a study of Aguas Zarcas using optical microscopy, scanning electron microscopy, and electron probe microanalysis, focusing on brecciation and aqueous alteration on the parent body. We observed two lithologies within our sample, separated by a distinct textural and chemical boundary. The first lithology has a higher chondrule abundance (“chondrule-rich”) and significantly larger FGRs compared to the second lithology (“chondrule-poor”), even for similarly sized chondrules. We observed clear compositional differences between the two lithologies and more multilayered FGRs in the chondrule-rich lithology. We determined that the chondrule-rich lithology is less altered (petrologic type 2.7–2.8) and displays larger FGRs to chondrule ratios compared to the more altered chondrule-poor lithology (petrologic type 2.5–2.6). These observations are contrary to previous models that predict aqueous alteration as a cause of FGR formation in the parent body. Our observed differences in Mg and Fe distribution in the lithology matrices alongside variable FGR thickness suggest distinct formation environments. We propose that the Aguas Zarcas parent body was subjected to several minor and major brecciation events that mixed different materials with variable degrees of aqueous alteration together, in agreement with previous studies.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2357-2372"},"PeriodicalIF":2.2,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142170340","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":"Detection and quantification of organosulfur species in the Tagish Lake Meteorite by highly sensitive LC-MS","authors":"N. Randazzo,&nbsp;R. W. Hilts,&nbsp;M. C. Holt,&nbsp;C. D. K. Herd,&nbsp;B. Reiz,&nbsp;R. M. Whittal","doi":"10.1111/maps.14189","DOIUrl":"https://doi.org/10.1111/maps.14189","url":null,"abstract":"<p>We analyzed the methanol extracts of six pristine specimens of the Tagish Lake meteorite (TL1, TL4, TL5A, TL6, TL7, and TL10a) and heated and unheated samples of Allende using high-performance liquid chromatography coupled with high-resolution, accurate mass–mass spectrometry (HPLC-HRAM-MS). All samples contained ppm levels of sulfate and methyl sulfate. The most abundant organosulfur compound in the methanol extracts of the Tagish Lake and Allende samples was methyl sulfate, which was likely formed primarily via an esterification reaction between intrinsic sources of methanol and sulfate. A homologous series of polythionic acids was also observed in the extracts of the Tagish Lake specimens and Allende. The polythionic acids were the most abundant soluble inorganic sulfur species found in the meteorites. Our results were confirmed using retention time, accurate mass, isotope matching, and tandem mass spectrometry (MS/MS). Hydroxymethanesulfonic acid, previously reported in Tagish Lake, was found only in an unheated Allende sample and in low abundance. Here, we propose possible sulfate formation pathways that begin with interstellar dimethyl sulfide, dimethyl disulfide, methyl sulfide, or methanethiol via cold, nebular processes within the interstellar medium and continue via MSA as an intermediary compound ending within planetary bodies with sulfate and methyl sulfate as the final products.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2241-2259"},"PeriodicalIF":2.2,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14189","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142170288","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":"Arya Udry citation for the 2022 Nier Prize","authors":"Harry Y. McSween","doi":"10.1111/maps.14221","DOIUrl":"https://doi.org/10.1111/maps.14221","url":null,"abstract":"","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 S1","pages":"A495"},"PeriodicalIF":2.2,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142077993","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":"The fireball of November 24, 1970, as the most probable source of the Ischgl meteorite","authors":"Maria Gritsevich,&nbsp;Jarmo Moilanen,&nbsp;Jaakko Visuri,&nbsp;Matthias M. M. Meier,&nbsp;Colin Maden,&nbsp;Jürgen Oberst,&nbsp;Dieter Heinlein,&nbsp;Joachim Flohrer,&nbsp;Alberto J. Castro-Tirado,&nbsp;Jorge Delgado-García,&nbsp;Christian Koeberl,&nbsp;Ludovic Ferrière,&nbsp;Franz Brandstätter,&nbsp;Pavel P. Povinec,&nbsp;Ivan Sýkora,&nbsp;Florian Schweidler","doi":"10.1111/maps.14173","DOIUrl":"https://doi.org/10.1111/maps.14173","url":null,"abstract":"<p>The discovery of the Ischgl meteorite unfolded in a captivating manner. In June 1976, a pristine meteorite stone weighing approximately 1 kg, fully covered with a fresh black fusion crust, was collected on a mountain road in the high-altitude Alpine environment. The recovery took place while clearing the remnants of a snow avalanche, 2 km northwest of the town of Ischgl in Austria. Subsequent to its retrieval, the specimen remained tucked away in the finder's private residence without undergoing any scientific examination or identification until 2008, when it was brought to the University of Innsbruck. Upon evaluation, the sample was classified as a well-preserved LL6 chondrite, with a W0 weathering grade, implying a relatively short time between the meteorite fall and its retrieval. To investigate the potential connection between the Ischgl meteorite and a recorded fireball event, we have reviewed all documented fireballs ever photographed by German fireball camera stations. This examination led us to identify the fireball EN241170 observed in Germany by 10 different European Network stations on the night of November 23/24, 1970, as the most likely candidate. We employed state-of-the-art techniques to reconstruct the fireball's trajectory and to reproduce both its luminous and dark flight phases in detail. We find that the determined strewn field and the generated heat map closely align with the recovery location of the Ischgl meteorite. Furthermore, the measured radionuclide data reported here indicate that the pre-atmospheric size of the Ischgl meteoroid is consistent with the mass estimate inferred from our deceleration analysis along the trajectory. Our findings strongly support the conclusion that the Ischgl meteorite originated from the EN241170 fireball, effectively establishing it as a confirmed meteorite fall. This discovery enables to determine, along with the physical properties, also the heliocentric orbit and cosmic history of the Ischgl meteorite.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 7","pages":"1658-1691"},"PeriodicalIF":2.2,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.14173","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141583752","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":"Petrological, chemical, and chronological study of breccias in the Chang'e-5 soil","authors":"Yuruo Shi,&nbsp;Wenxiao Peng,&nbsp;Katherine H. Joy,&nbsp;Xuefeng Yu,&nbsp;Yue Guan,&nbsp;Zemin Bao,&nbsp;Xiaochao Che,&nbsp;Romain Tartèse,&nbsp;Joshua F. Snape,&nbsp;James W. Head,&nbsp;Martin J. Whitehouse,&nbsp;Xiaolei Wang,&nbsp;Yuqi Qian,&nbsp;Zengsheng Li,&nbsp;Chen Wang,&nbsp;Tao Long,&nbsp;Shiwen Xie,&nbsp;Runlong Fan,&nbsp;Jianhui Liu,&nbsp;Zhiqing Yang,&nbsp;Chun Yang,&nbsp;Peizhi Wang,&nbsp;Shoujie Liu,&nbsp;Zhen Wang,&nbsp;Haibin Huang,&nbsp;Yuelan Kang,&nbsp;Huiyi Sun,&nbsp;Wei Zhang,&nbsp;Lanlan Tian,&nbsp;Huawei Li,&nbsp;Xiaohong Mao,&nbsp;Wei Shan,&nbsp;Dapeng Li,&nbsp;Dunyi Liu,&nbsp;Alexander A. Nemchin","doi":"10.1111/maps.14192","DOIUrl":"https://doi.org/10.1111/maps.14192","url":null,"abstract":"<p>We carried out a petrological, mineralogical, and geochemical study of fragmental and regolith breccia clasts separated from two Chang'e-5 (CE-5) soil samples, CE5C0000YJYX03501GP and CE5C0400, which provide an opportunity to investigate the compositional change of regolith at the landing site through time. Fragmental breccia CE-5-B3 contains a diverse range of basaltic clasts and basaltic mineral fragments, and some rare Mg-suite-like minerals. Regolith breccias CE-5-B006, CE-5-B007, CE-5-B010-08, CE-5-B010-09, CE-5-B011-07, and CE-5-B016-03 contain mare basaltic fragments, mare vitrophyric clasts, rare Mg-rich fragments possibly derived from the Mg-suite rocks, and impact-derived glass spherules. Pb-isotope data obtained for baddeleyite grains found both inside some of the basaltic clasts identified in breccia fragments and in the breccia matrices yield Pb/Pb dates similar to the 2 Ga crystallization age of the CE-5 basalt fragments, extracted directly from the soil sample. Seventy-four Pb isotope analyses of Ca-phosphate grains also indicate that the majority of these grains have Pb/Pb dates of 2 Ga, suggesting that they originate from the CE-5 basalts. In addition, a Pb–Pb isochron drawn through analyses of four Ca-phosphates in breccia CE5-B006 yielded an intercept corresponding to a date of 3871 ± 46 Ma, which is the best possible estimate of the formation age of these four grains. Electron probe microanalysis shows that the breccias contain components similar to CE-5 mare basalt fragments extracted directly from the soil sample, implying that the fragmental and regolith breccia fragments are mostly composed of material sourced from the underlying basalts. The general absence of impact melt breccia clasts, along with the general lack of Fe–Ni metal and absence of added meteoritic debris all suggest that the regolith at the CE-5 landing site is immature and dominated by material mixed together by small local impact cratering events. Trace element analyses show that the glass beads in the regolith breccias have a Th abundance of 4.06–5.28 μg g⁻¹. This is similar to the Th content of the regolith above the Em4 unit at the landing site as measured from orbit, as well as the estimated bulk Th content of CE-5 basalts, suggesting that Th of the local regolith is predominantly sourced from the underlying mare basalts, without significant Th addition from Th-rich exotic clasts sourced from evolved lunar lithologies.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 9","pages":"2296-2320"},"PeriodicalIF":2.2,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142170338","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":"Compositional evidence for chondrule origins of low-Ca pyroxenes in comet Wild 2 and a giant cluster IDP","authors":"D. J. Joswiak,&nbsp;D. E. Brownlee,&nbsp;A. J. Westphal,&nbsp;Z. Gainsforth,&nbsp;M. Zhang,&nbsp;N. T. Kita","doi":"10.1111/maps.14187","DOIUrl":"10.1111/maps.14187","url":null,"abstract":"<p>A literature compilation of 1136 low-Ca pyroxene compositions from chondrules from 12 primitive type 2–3 carbonaceous, ordinary and enstatite chondrite groups define unique regions on an Al₂O₃ and Cr₂O₃ diagram when compared to low-Ca pyroxenes from equilibrated type 4-6 chondrites. Measured compositions of 100 low-Ca pyroxenes from comet Wild 2 and a giant cluster IDP of probable cometary origin are similar to each other and fall in the type 2–3 chondrite chondrule region suggesting that most of the pyroxenes likely formed in the solar nebula like conventional chondrules. The data imply that most low Ca-pyroxenes from comet Wild 2 and the giant cluster IDP formed from igneous crystallization processes and did not experience significant thermal metamorphism, indicating that the low-Ca pyroxenes were unlikely incorporated into large parent bodies prior to accretion in their respective comet bodies. An intriguing group of nine low-Ca pyroxenes from comet Wild 2 with low Cr and Al that fall where type 4–6 chondrites are located are interpreted as products of condensation. The compositional data combined with previously measured oxygen isotopes on 17 low-Ca pyroxenes support earlier conclusions that comet samples have links with carbonaceous, ordinary, and possibly enstatite chondrite groups. Our results provide additional evidence that comets accreted materials from multiple chondrule reservoirs throughout the solar nebula.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"59 7","pages":"1790-1819"},"PeriodicalIF":2.2,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141105545","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}