¹Paul L. Broughton
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13809]
¹Broughton and Associates, P.O. Box 6976, Calgary, Alberta, T2P 2G2 Canada
Published by arrangement with John Wiley & Sons

Meteorite impact-induced mobilization of a volcanic ash tuff resulting in 100s of m long lithified clastic dikes is a novel mechanism in the geologic record. The Paleogene Eagle Butte impact event in southeastern Alberta, western Canada, resulted in a 10–17 km diameter central peak crater, now partially eroded and buried without expression at the surface. Impact shock waves, degraded to elastic waves, mobilized sediment 10s  of km beyond the crater and resulted in a cluster of 100s  of m long, 10–20 cm thick, dikes consisting of volcanic ash. It is not well understood how effective meteorite impact-induced waves would be as triggers for sediment mobilization at areas 10s of km distant from an impact crater. Emplacement of the Manyberries dike cluster provides insight into this issue and confirms that shock waves, degraded to elastic waves, can indeed liquefy and mobilize sediments at distances as much as 5 crater radii beyond an impact site. These impact-induced waves triggered liquefaction and mobilization of a shallowly buried Campanian-Maastrichtian deposit of volcanic ash and injected the tuff sediment along impact-induced faults. The lithification of the dike tufa, consisting of the cristobalite–tridymite groundmass, resulted from partial dissolution of glass shards and precipitation of opaline cement. These weathering resistant dikes of indurated tuff sediment extend for as much as 800 m on recessive Campanian-Maastrichtian shale ridges of the badlands topography.

^1,2Gabriel A. Pinto,²Yves Marrocchi,³Emmanuel Jacquet,¹Felipe Olivares
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13812]
¹Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile
²Université de Lorraine, CNRS, CRPG, UMR 7358, Vandœuvre-lès-Nancy, 54501 France
³Instituto de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, Paris, 75005 France
Published by arrangement with John Wiley & Sons

Chondrules are commonly surrounded by fine-grained rims (FGRs) whose origin remains highly debated; both nebular and parent body settings are generally proposed. Deciphering their origin, however, is of fundamental importance as they could clarify the matrix–chondrule relationship and thus constrain the formation and transport conditions of chondrules in the circumsolar disk. Here, we report a systematic survey of FGRs in CO, CM, CV, and CR chondrites; we compare (i) the thickness of FGRs to the size of their host chondrules and (ii) the frequency of FGRs to the modal abundance of matrix in the respective host chondrites. Although FGRs show textural variations depending on the petrologic type of the considered chondrites, our data show a positive correlation between apparent rim thickness and the radius of the host chondrule in all chondrite groups. We also found a positive correlation between the evaluated percentages of rimmed chondrules and the modal abundance of matrix material in the chondrites. We show that this relationship could not result from parent body processes, whether matrix compaction or FGR fragmentation. Therefore, we propose that FGRs were accreted under warm conditions at the end of chondrule-forming events. Our results thus support (i) a nebular origin for FGR, whose abundances are directly related to the abundance of available dust in regions of chondrite accretion; and (ii) the accretion of chondrites from locally formed chondrules and matrix, suggesting limited radial transport in the protoplanetary disk.

^1,2Atmane Lamali,^1,2Lamine Hamai,³Sid Ahmed Mokhtar,¹Abdelkrim Yelles-Chaouche,¹Abdeslam Abtout,¹Nacer Merabet,²Salah Eddine Bentridi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13804]
¹Centre de Recherche en Astronomie Astrophysique et Géophysique, Route de l’Observatoire, BP 63, Algiers, Algeria
²Laboratoire de l’Énergie et des Systèmes Intelligents (LESI), Faculté des Sciences, et de la Technologie, Université Djillali Bounaâma Khemis Miliana, Route de Théniat El Had, Ain Defla, Khemis Miliana, 44225 Algeria
³Centre de recherche nucléaire de DRARIA, BP 43, Draria, Algiers, Sebala, Algeria
Published by arrangement with John Wiley & Sons

Among all geophysical methods, gamma ray spectrometry is not widely used in impact cratering studies, despite its efficiency in the investigation of physical/chemical changes in rocks. The application of gamma ray spectrometry method to data from the Maâdna crater is aimed at detection and verification of the presumed impact-derived melt rocks or breccias, as well as discussing its implications on process of formation. The resulting information also demonstrates the potential of these specific data regarding our general understanding of impact cratering, while a few case studies have been reported in the literature to date within the impact community. Maâdna crater is dated at 2.6–3.1 Ma of ~1.7 km and is emplaced in Upper-Cretaceous to Eocene limestones of the northern part of the Algerian Saharan platform. Although originally accepted as an impact crater, its origin is still controversial. Several thousands of field measurements were taken using a field portable gamma ray spectrometer. The measurements can be equivalently expressed by up to about 42 km footpath recordings in real-time ground acquisitions, covering the entire structure and surrounding areas beyond the crater edge. The collected data included the total count (Tc) and the concentrations of the radionuclides calculated in wt% for K and in ppm for U and Th. The spectra rates recorded inside and outside the crater did not exceed the maximum average concentrations corresponding to 75.3 Cps, 4.94 ppm, 10.5 ppm, and 1.79 wt% for Tc, U, Th, and K, respectively. The database was processed using various gridding data methods, from which the minimum curvature was adopted as it provides a powerful visualization and interpretation of the anomalous distribution of radioactive elements and their corresponding ratios maps. In addition, an improved statistical analysis was carried out in order to extract a maximum of information about the radiometric response of each rock unit. This analysis consisted of a series of multiple linear regression, mean differencing, Q–Q (quantile–quantile) plots, and ternary mapping. Maps and plots of various models allowed us to examine the background variability in the distribution of K, Th, and U concentrations at the surface of the three distinctive litho-type zones in the surveyed area, which are the central part, the crater edge, and the outside of the crater including the wadi deposits. Observed results of different radiometric responses clearly reflect the effect of various lithological units, especially in the areas with high K concentration. Note that this positive K-anomaly has been observed in recent deposits that fill the Maâdna depression or external wadi beds. In contrast, the surrounding limestone rocks showed lower levels of radioelement concentrations. Relevant similarities found between the radiometric signatures of the Neogene formations inside and outside the crater can be considered as a strong argument to exclude preferential radionuclides enrichment caused by an impact event. Consequently, the natural origin of radioactive sources can be easily explained. Compared to other radiometric signatures documented on proven impact structures, the Maâdna structure has been notably discussed in the context of a diapiric hypothesis rather than a meteoritic one. Moreover, the methods used here contribute to our knowledge of the regional sedimentary history in terms of natural radioactivity.

^1,2Bastien Soens,^3,4Stepan M.Chernonozhkin,³Claudia González de Vega,³Frank Vanhaecke,⁵Matthias van Ginneken,¹Philippe Claeys,¹Steven Goderis
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.03.029]
¹Analytical-, Environmental-, and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium
²Laboratoire G-Time, Université Libre de Bruxelles 50, Av. F.D. Roosevelt CP 160/02, BE-1050 Brussels, Belgium
³Department of Chemistry, Ghent University, Krijgslaan 218 Building S12, BE-9000 Gent, Belgium
⁴Chair of General and Analytical Chemistry, Research group – Isotope ratio analysis, Montanuniversität Leoben, Franz Josef-Straße 18, 8700 Leoben, Austria1
⁵Centre for Astrophysics and Planetary Science, University of Kent, CT2 7NZ, Canterbury, Kent, United Kingdom
Copyright Elsevier

Achondritic micrometeorites represent one of the rarest (ca. 0.5–2.1%) particle types among Antarctic micrometeorite collections. Here, we present major, trace element and oxygen isotope compositions on five vitreous, achondritic cosmic spherules (341–526 µm in size) recovered from the Widerøefjellet sedimentary trap in the Sør Rondane Mountains (SRMs) of East Antarctica. We also present the first iron isotope data for four of these achondritic cosmic spherules. The particles were initially identified based on the atomic concentrations of Fe-Mg-Mn and their distribution in Fe/Mg versus Fe/Mn space, spanning a relatively wide range in Fe/Mg ratios (ca. 0.48–1.72). The Fe/Mn ratios cover a more restricted range (22.4–31.7), comparable to or slightly below the values measured for howardite-eucrite-diogenite (HED) and martian meteorites. One particle (WF1801-AC3) displays an elevated Fe/Mn ratio of ∼78, comparable to the values determined for lunar rocks. The negative correlation observed between the CaO+Al2O3 contents and the Fe/Si ratios of achondritic spherules reflects both the mineralogy of the precursor materials, as well as the extent of volatilization experienced during atmospheric entry heating. This trend suggests that the primary mineralogy of precursor materials may have been compositionally similar to basaltic achondrites. Based on their distribution in Ca/Si versus Al/Si space, we argue that the majority of achondritic cosmic spherules predominantly sample pyroxene- and/or plagioclase-rich (i.e., basaltic) precursor bodies. Such precursor mineralogy is also inferred from their rare earth element (REE) patterns, which show resemblances to fine-grained basaltic eucrites or Type 1 achondritic spherules (n = 3 – av. REEN = 11.2–15.5, (La/Yb)N = 0.93–1.21), pigeonite-rich equilibrated eucrite precursors or Type 2 achondritic spherules (n = 1 – av. REEN = 27.9, (La/Yb)N = 0.10), and possibly Ca-phosphates from (primitive) achondritic bodies (n = 1 – av. REEN = 58.8, (La/Yb)N = 1.59). This is clearly demonstrated for particle WF1801AC-1, which was likely inherited from a fine-grained eucritic precursor body. The pre-atmospheric oxygen isotope composition was reconstructed through compensation of mass-dependent fractionation processes as well as mixing with atmospheric oxygen, using iron isotope data. Two particles (WF1801AC-2, WF1801-AC4) display corrected oxygen isotope compositions (δ18O = 3.7–4.4‰) largely consistent with HED meteorites and may thus originate from HED-like parent bodies. The corrected oxygen isotope compositions (δ18O = 12.6–12.8‰) of the remaining particles (WF1801-AC3, WF1801-AC5) do not correspond to known meteorite fields and may represent two distinct types of unknown achondritic parent bodies or residual atmospheric entry effects. Finally, the abundance (ca. 0.5%) of achondritic cosmic spherules within the Widerøefjellet sedimentary trap is comparable to that observed in the South Pole Water Well (SPWW – ca. 0.5%), Novaya Zemlya glacier (ca. 0.45%) and Transantarctic Mountain (TAM) (ca. 2.1%) collections, confirming their overall rarity in micrometeorite collections. Unambiguous evidence for micrometeorites from the Moon or Mars remains absent from collections to date.

^1,2Hamed Pourkhorsandi,¹Jérôme Gattacceca,¹Pierre Rochette,³Thomas Smith,⁴Lydie Bonal,⁵Massimo D’Orazio,¹Bertrand Devouard,¹Corinne Sonzogni,²Vinciane Debaille
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13801]
¹CNRS, IRD, INRAE, CEREGE, Aix-Marseille Univ, Aix-en-Provence, France
²Laboratoire G-Time, Université Libre de Bruxelles, CP 160/02, 50, Av. F.D. Roosevelt, Brussels, 1050 Belgium
³Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beitucheng Western Road Chaoyang District, Box 9825, Beijing, 100029 China
⁴Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France
⁵Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
Published by arrangement with John Wiley & Sons

The Famenin meteorite fell around 08:30 a.m. local time (GMT+4.5) on June 27, 2015 on the roof of a house in Famenin, a town in NW Iran. A single 640 g stone was recovered, shattered into several pieces upon impact. The shape of the impact hole and the relative position of the recovered meteorites indicate a N-NW fall direction. Famenin is an ordinary chondrite (OC) with well-preserved chondrules of various types, (Fe,Ni) metal, troilite, phosphate, and chromite. The organic matter systematics and the olivine and low-Ca compositional distributions (percent mean deviations 18% and 31%, respectively) indicate it is a type 3.4/3.8 chondrite. Considering the average chemical compositions of olivine (Fa17.5±4.7) and low-Ca pyroxene (Fs16.8±7.5), average Co content of the kamacite (5.6 mg g−1), and Cu/Ni and Ga/Ni ratios, Famenin should be classified as an H chondrite. However, saturation magnetization is 26.0 Am2 kg−1, indicating a bulk metal content similar to L chondrites. Similarly, the whole-rock Ni and Co contents (13073 and 540 µg g−1, respectively), and average chondrule diameter (550 µm) are closer to typical values for L chondrites than H chondrites. The (Fe,Ni) metal modal abundance (5 vol%), magnetic susceptibility, and possibly whole-rock oxygen isotopic composition indicate intermediate properties between H and L chondrites. Noble gas composition and cosmic-ray exposure ages of Famenin and El Médano 195 (another intermediate OC) shows their gas-rich character and an older ejection age from their parent body than those for the majority of H and L chondrites. Famenin, together with similar intermediate OCs, increases the diversity of this meteorite clan and suggests the existence of a separate OC group with a composition broadly intermediate between H and L groups for which a different designation (HL) is proposed. OCs likely originate from more than three parent bodies (H, L, and LL) as traditionally proposed.

¹Robert W. Nicklas,¹James M. D. Day,²Zoltan Vaci,³Arya Udry
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13805]
¹Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093 USA
²Department of Earth and Planetary Science, Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87131 USA
³Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, Nevada, 89154 USA
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 8686 is an olivine-phyric shergottite containing up to ~500 μm long olivine crystals in a fine-grained groundmass of augite, pigeonite, and maskelynite, with accessory merrillite, pyrrhotite, and oxides. Bulk rock and mineral major and trace element concentrations are reported for NWA 8686, along with bulk rock highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances and 187Re-187Os data. Based on its mineralogy, texture, and bulk rock rare earth element (REE) abundances, NWA 8686 is classified as an intermediate olivine-phyric shergottite. It is notable for having some of the most ferroan olivine macrocrysts (forsterite content = 51.5 ± 3.5) of any olivine-phyric shergottite. Olivine is absent from the NWA 8686 groundmass, which is unique for olivine-phyric shergottites, and the calculated groundmass composition is also not olivine normative. The bulk meteorite has a low Mg# of 59 yet has HSE in broadly chondritic proportions (~0.005 × CI chondrite). The bulk rock REE pattern for NWA 8686 shows depletions in both the light and heavy REE relative to the middle REE. Compiled olivine and bulk rock data for olivine-phyric shergottites indicate that olivine macrocrysts in almost all these meteorites are the result of entrainment of antecrysts or xenocrysts. The combination of low Mg# and chondritic HSE signatures in NWA 8686 means that it may have been formed either from the mixing between an evolved lava and early-formed HSE-rich phases such as Os-Ir alloys or by the melting of a low Mg# mantle source with chondritic HSE abundances. The elevated Gd/Yb ratio in both NWA 8686 and other intermediate olivine-phyric shergottites indicates that garnet was involved as either a residual or fractionating phase in their petrogenesis.

¹Marina Martínez,¹Adrian J.Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.03.019]
¹Department of Earth & Planetary Sciences, MSC03-2040, 1University of New Mexico, Albuquerque, NM 87131, USA
Copyright Elsevier

Queen Alexandra Range (QUE) 99177 is one of the least altered CR carbonaceous chondrite known, with mineralogical and isotopic characteristics that indicate a high level of pristinity. In this study, we have examined the so-called smooth rims that surround many type I chondrules in QUE 99177, using SEM, EPMA, and FIB-TEM techniques. We have characterized their constituent phases to unravel the precursor material(s) of smooth rims, assess their formation mechanisms, and constrain the conditions of the altering fluid. Smooth rims are the most common type of rims around type I chondrules and exclusively occur around chondrules with Silica-rich Igneous Rims (SIRs). Smooth rims consist of an Fe-rich, hydrous silicate material that is Si- and Fe-rich, with minor Mg, Al, Ca, and Mn, and gives low analytical totals measured by EPMA. TEM observations reveal that the Fe-rich silicate phase is an amorphous gel that contains unaltered crystalline phases and igneous glass. Crystalline phases consist of igneous, unaltered, zoned pyroxenes with compositions consistent with pyroxenes in SIRs, as well as albite and chromite. The amorphous gel preserves previous crystal outlines with morphologies consistent with silica (cristobalite) grains in SIRs and has a composition identical to pseudomorphic silica replacements in SIRs. Based on these observations, we conclude that smooth rims derive from low-temperature aqueous alteration of silica in SIRs by an Fe-rich fluid. We suggest that the Fe was derived by leaching of amorphous silicates in the matrix, which reacted rapidly with melted water ice, although alteration of Fe,Ni metal blebs in SIRs could potentially be an additional source of Fe. Silica underwent dissolution and replacement whereas feldspar and glass remained unaltered because (1) the fluid was slightly alkaline, (2) cristobalite has a reaction rate much higher than quartz and feldspar, and (3) the alteration was very limited and fast, indicating that it was due solely to melting of accreted water ice and there was no introduction of additional fluid from external sources.

¹Nabawy, B.S.
Natural Resources Research 31, 179-189 Open Access Link to Article [DOI 10.1007/s11053-021-10007-6]
¹Department of Geophysical Sciences, National Research Centre, 33 ElBohouth street, P.O. 12311, Dokki, Cairo, Egypt

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^1,2Ishiguro M. et al. (>10)
Monthly Notices of the Royal Astronomical Society 509, 4128-4142 Link to Article [DOI 10.1093/mnras/stab3198]
¹Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
²Snu Astronomy Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea

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¹Ming Jin,¹Xiaozhong Ding,¹Hunying Han,¹Jianfeng Pang,^1,2Ying Wang
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115008]
¹Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
²Graduate School of Chinese Academy of Geological Sciences, Beijing 100037, China
Copyright Elsevier

Mineral abundance quantification of lunar surface materials using remotely acquired spectra can be achieved with spectral unmixing methods, but this has remained a challenging problem. The existing unmixing methods neglect the existence of widespread glass material and the spectral similarity of different minerals. To solve this problem, this study proposes a method to calculate the main mineral abundances in lunar regolith based on reflectance spectra by utilizing Fisher transformation combined with multiple endmember spectral mixture analysis (MESMA). A set of spectra of lunar main constituents, including plagioclase, pyroxene, ilmenite, olivine and glass material, were selected from the RELAB spectral database and used as endmembers. The endmember spectra were utilized to compute the projection vectors, with which the spectral characteristics can be transformed into low-dimensional Fisher space in which intraclass spectral variability can be minimized while the interclass variability of different mineral spectra can be maximized. The endmember spectra and the lunar soil spectra in the Lunar Soil Characterization Consortium (LSCC) dataset were both transformed into Fisher space, in which MESMA was executed to acquire the fraction of each endmember. MESMA allows for comprehensive endmember expressions by representing a type of mineral using multiple spectra rather than a single endmember. Compared with laboratory mineral measurements, this approach estimated the mineral abundances with determination coefficient R2 values equal to 0.88 and 0.65 in the lunar mare and highland regions, respectively. After validation with laboratory data, the method was further applied at the regional scale where Apollo 12 and Apollo 16 landed by using M3 images, and the estimated accuracy of different minerals was similar to that of the laboratory spectra.