^1,2Raiza R. Quintero,²Aaron J. Cavosie,^3,4Sanna Alwmark,⁵Peter W. Haines,⁶Martin Danišík,²Nicholas E. Timms,⁷David Lim
Meteoritics & Planetary Science (in Press) Link to Artticle [https://doi.org/10.1111/maps.14108]
¹Department of Geology, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico
²Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth,
Western Australia, Australia
³Department of Geology, Lund University, Lund, Sweden
⁴Niels Bohr Institute, University of Copenhagen, Copenhagen N, Denmark
⁵Geological Survey of Western Australia, East Perth, Western Australia, Australia
⁶John de Laeter Centre, Curtin University, Perth, Western Australia, Australia
⁷Maria Resources Pty. Ltd., Subiaco, Western Australia, Australia
Published by arrangement with John Wiley & Sons

The Ilkurlka structure is an ~12 km diameter buried circular aeromagnetic anomaly within the Officer Basin in Western Australia. Prior studies postulated a range of origins, including meteorite impact. We report the presence of pervasive deformation in the first drill cores from the structure. Brecciated sandstone and siltstone contain arrays of quartz grains with concussion fractures and rare shocked quartz grains with planar deformation features (PDF). Universal stage measurements of two quartz grains reveal one grain with PDF parallel to (0001) orientation and three PDF sets parallel to {10⁢1¯⁢3}. A second grain contains three PDF sets parallel to {10⁢1¯⁢3} and one set parallel to {10⁢1¯⁢4}. The shocked grains are interpreted to have formed in situ, rather than representing transported detrital shocked grains. These results suggest local shock compression of at least 10 GPa; however, preservation of primary porosity and overall paucity of shocked grains may indicate lower mean shock pressures. (U-Th)/He dating of 58 apatite grains from four samples across both cores shows a dominant age population at ~265 Ma and a minor age population at ~135 Ma. These dates overlap with regional events and thus do not provide an unambiguous impact age. An upper Carboniferous to lower Permian maximum impact age is provisionally proposed based on inferred missing target rock stratigraphy.

¹George D. Cody et al.(>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14096]
¹Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
Published by arrangement with John Wiley & Sons

This study analyzed samples of the Murchison and Sutter’s Mill carbonaceous chondrite meteorites in support of the future analysis of samples returned from the asteroid (10155) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission. Focusing specifically on the insoluble organic matter (IOM), this study establishes that a total of 1.3 g of bulk sample from a single chondritic meteorite are sufficient to obtain a wide range of cosmochemical information, including light element analysis (H, C, and N), isotopic analysis (D/H, 13C/12C, and 15N/14N), and x-ray fluorescence spectroscopy for major elemental abundances. IOM isolated from the bulk meteorite samples was analyzed by light element and isotopic analysis as described above, 1H and 13C solid-state nuclear magnetic resonance spectroscopy, Raman spectroscopy, and complete noble gas analyses (abundances and isotopes). The samples studied included a pair from Murchison (CM2), one of which had been irradiated with high-energy x-rays in the course of computed tomographic imaging. No differences between the irradiated and non-irradiated Murchison samples were observed in the many different chemical and spectroscopic analyses, indicating that any x-ray–derived sample damage is below levels of detection. Elemental, isotopic, and molecular spectroscopic data derived from IOM isolated from the Sutter’s Mill sample reveals evidence that this meteorite falls into the class of heated CM chondrites.

¹B. G. Rider-Stokes,^1,2M. Anand,¹L. F. White,³J. R. Darling,⁴R. Tartèse,⁵M. J. Whitehouse,¹I. Franchi,¹R. C. Greenwood,¹G. Degli-Alessandrini
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14102]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
²Department of Mineralogy, The Natural History Museum, London, UK
³School of the Environment, Geography & Geosciences, University of Portsmouth, Portsmouth, UK
⁴Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
⁵Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
Published by arrangement with John Wiley & Sons

As some of the oldest differentiated materials in our solar system, angrite meteorites can provide unique insights into the earliest stages of planetary evolution. However, the timing of planetary mixing, as evidenced by oxygen isotope variations in the quenched angrites, and the extent of magmatism on the angrite parent body (APB) remain poorly understood. Here, we report on microstructurally guided in situ geochemical and Pb–Pb isotopic measurements on angrites aimed at better understanding of the timing and nature of magmatic processes, as well as impact events, on the APB. The quenched angrite Northwest Africa (NWA) 12320 yielded a Pb–Pb date of 4571.2 ± 9.4 Ma, which we interpret as corresponding to the timing of planetary mixing. The only known shocked quenched angrite, NWA 7203, also yielded an ancient Pb–Pb date of 4562.9 ± 9.3 Ma, which is identical to the Pb–Pb date of 4563.6 ± 7.9 Ma obtained for the texturally intermediate angrite NWA 10463. Pb–Pb analyses in phosphates in the dunitic angrite NWA 8535 yielded a much younger date of 4514 ± 30 Ma, representing the youngest Pb–Pb date ever recorded for an angrite. Based on the evidence from the lack of shock deformation, olivine major and trace element compositions, and no apparent contamination in the oxygen isotope composition of NWA 8535, our findings are consistent with prolonged magmatism on the APB. This finding is consistent with a large size for the APB.

¹Andrew Schedl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14103]
¹Department of Chemistry and Physics, West Virginia State University, Institute, West Virginia, USA
Published by arrangement with John Wiley & Sons

Jeptha Knob is a deformed structure, 4.5 km in diameter, composed entirely of carbonate rocks in the stable craton of North America. At Jeptha Knob, conventional evidence of meteorite impact, shock metamorphism, has not been found. I used calcite twin analysis to test the hypothesis that Jeptha Knob is a meteorite impact crater. Calcite twinning gives differential stresses of >170 MPa in rocks that were 600 to ≈800 m below the surface when the rocks were deformed. Under these conditions, high differential stresses cannot be explained by tectonic processes. In addition, twin intensities are >150 twins/mm which are >50% higher than the highest twin intensities observed in limestone from a wide variety of tectonic settings. Twin intensities and differential stresses are the same magnitudes as those found at Serpent Mound, a proven impact structure. Consistent with meteorite impact, differential stresses increase toward the center of the structure. If one accepts that Jeptha Knob is a marine impact crater, then (1) the presence of high temperature (>250°C) thick twins in calcite from a resurge deposit; (2) the extensive dolomitization of the central uplift with water/rock ratios >1.0; and (3) two episodes of calcite twin recorded incremental strains, are explained.

¹Yang He,^1,2Ai-Cheng Zhang,^3,4Yongbo Peng,^2,5Jia Liu,^2,5Liping Qin
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.11.013]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetology, China
³International Center for Isotope Effects Research, Nanjing University, Nanjing 210023, China
⁴School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
⁵CAS Key Laboratory of Crust-Mantle Materials and Environment, University of Science and Technology of China, Hefei 230026, China
Copyright Elsevier

Angrites are a small group of basaltic meteorites and their origin is currently disputed. Among these, Northwest Africa (NWA) 12774 is a quenched angrite that was reported having an anomalously high bulk Cr₂O₃ content (∼0.45 wt%). However, the reason behind this anomaly, which is critical for understanding the evolution of the angrite parent body, remains unknown. Here, we performed a detailed petrographic, mineralogical, and bulk oxygen and chromium isotopic composition study on this meteorite. NWA 12774 consists of porous olivine macrocrysts, phenocrysts of olivine and Al-Ti-rich augite, and spinel micro-phenocrysts with fine-grained groundmass. The olivine macrocrysts and the magnesian cores of olivine phenocrysts show compositional correlations distinctly different from typical olivine phenocrysts. The olivine macrocrysts contain small chromite/chrome-spinel inclusions which have the highest Cr₂O₃ content (53.2 wt%) for chromite/spinel in angrites to date. Based on these textural and chemical features, the olivine macrocrysts and the magnesian cores of olivine phenocrysts are identified as xenocrysts. Some pyroxene phenocrysts contain regions with complexly zoned microtextures, which have much larger chemical variations compared with those with simple zoned microtextures. The regions with complexly zoned microtextures are likely to be of xenocrystic origin. The bulk Cr₂O₃ content in NWA 12774 was estimated through two approaches, both of which show the bulk Cr₂O₃ content to be around 0.3 wt% or possibly up to ∼0.45 wt%, which is consistent with previously measured values. The high Cr₂O₃ content in NWA 12774 could be attributed to both the high abundance of spinel micro-phenocrysts and their high Cr₂O₃ contents, rather than the presence of Cr-rich xenocrysts. The calculated melt REE concentration in NWA 12774 equilibrated with the most Mg-rich augite is essentially identical to those in LEW 87051 and Asuka 881371, which however have Cr₂O₃ contents much lower than NWA 12774. We suggest that the mantle source of NWA 12774 may not be as depleted in Cr and probably other volatile elements as other angrite sources. The various Cr₂O₃ contents in different quenched angrites probably reflect that their mantle sources have not been homogenized.

^1,2Eleanor S. Jennings,^2,3Peter Coull
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14106]
¹Birkbeck, University of London, London, UK
²The Centre for Planetary Sciences at UCL/Birkbeck, London, UK
³University College London, London, UK
Published by arrangement with John Wiley & Sons

Olivine-phyric shergottites are relatively young Martian meteorites that resemble primitive mantle-derived melts, so offer insight into the causes of recent magmatism on Mars. The Al-in-olivine geothermometer offers the potential to examine (near-)liquidus melt temperatures. However, the ubiquitous shock features in most Martian meteorites, caused by high-energy impacts, can change the structure and composition of olivine crystals, making the applicability of mineral geothermometry methods uncertain. This study examines microstructure and mineral chemistry in two shocked primitive, depleted olivine-phyric shergottites, Sayh al Uhaymir (SaU) 005 and Dar al Gani (DaG) 476. DaG 476 is unsuitable for Al-in-olivine thermometry because of the presence of difficult-to-observe but pervasive networks of undulating veins in olivine down to sub-micron sizes, caused by melting and providing pathways for cation diffusion. In contrast, SaU 005 can be used for Al-in-olivine thermometry despite the presence of conjugate shear and fracture sets and micron-scale cpx-spinel exsolution. The average crystallization temperature of Fo>70 olivine in SaU 005, 1380°C, is near-identical to the average temperature of new and published Fo>70 data from all olivine-phyric shergottites. When corrected for equilibrium with mantle olivine (Fo80) this corresponds to a mantle temperature of approximately 1500°C, 130°C hotter than ambient Martian mantle when shergottites formed. Shergottites were generated by melting within a moderately hot mantle plume or thermal anomaly, in support of other evidence that the Martian mantle is actively convecting. However, it does not support the extremely high potential temperatures estimated for the shergottite source by a whole-rock petrological method.

^1,2,3M. K. Weisberg,⁴M. E. Zolensky,⁵M. Kimura,^1,2,3K. T. Howard,^2,3D. S. Ebel,^2,3M. L. Gray,⁶C. M. O’D. Alexander
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14092]

¹Department of Physical Sciences, Kingsborough College CUNY, Brooklyn, New York, USA
²Department of Earth and Environmental Sciences, CUNY Graduate Center, New York, New York, USA
³Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁴ARES, NASA Johnson Space Center, Houston, Texas, USA
⁵National Institute of Polar Research, Tokyo, Japan
⁶Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
Published by arrangement with John Wiley & Sons

NWA 8785 is a remarkable EL3 chondrite with a high abundance (~34 vol%) of an Fe-rich matrix. This is the highest matrix abundance known among enstatite chondrites (ECs) and more similar to the matrix abundances in some carbonaceous and Rumuruti chondrites. X-ray diffraction and TEM data indicate that the fine-grained portion of the NWA 8785 matrix consists of nanoscale magnetite mixed with a noncrystalline silicate material and submicron-sized enstatite and plagioclase grains. This is the first report of magnetite nanoparticles in an EL3. The Si content of the metal (0.7 wt%), presence of ferroan alabandite, and its O isotopic composition indicate NWA 8785 is EL3-related. Having more abundant matrix than in other ECs, and that the matrix is rich in magnetite nanoparticles, which are not present in any other EC, suggest classification as an EL3 anomalous. Although we cannot completely exclude any of the mechanisms or environments for formation of the magnetite, we find a secondary origin to be the most compelling. We suggest that the magnetite formed due to hydrothermal activity in the meteorite parent body. Although ECs are relatively dry and likely formed within the nebular snow line, ices may have drifted inward from just beyond the snow line to the region where the EL chondrites were accreting, or more likely the snow line migrated inward during the early evolution of the solar system. This may have resulted in the condensation of ices and provided an ice-rich region for accretion of the EL3 parent body. Thus, the EL3 parent body may have had hydrothermal activity and if Earth formed near the EC accretion zone, similar bodies may have contributed to the Earth’s water supply. NWA 8785 greatly extends the range of known characteristics of ECs and EC parent body processes.

^1,2P.G. Brown et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14100]
¹Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada
²Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

The Golden (British Columbia, Canada) meteorite fall occurred on October 4, 2021 at 0534 UT with the first recovered fragment (1.3 kg) landing on an occupied bed. The associated fireball was recorded by numerous cameras permitting reconstruction of its trajectory and orbit. The fireball entered the atmosphere at a 54° angle from the horizontal at a speed of 18 km s−1. The fireball reached a peak brightness of −14, having first become luminous at a height of >84 km and ending at 18 km altitude. Analysis of the infrasonic record of the bolide produced an estimated mass of
kg while modeling of the fireball light curve suggests an initial mass near 70 kg. The fireball experienced a major flare near 31 km altitude where more than half its mass was lost in the form of dust and gram-sized fragments under a dynamic pressure of 3.3 MPa. The strength and fragmentation behavior of the fireball were similar to those reported for other meteorite-producing fireballs (Borovička et al., 2020). Seven days after the fireball occurred, an additional 0.9 kg fragment was recovered during the second day of dedicated searching guided by initial trajectory and dark flight calculations. Additional searching in the fall and spring of 2021–2022 located no additional fragments. The meteorite is an unbrecciated, low-shock (S2) ordinary chondrite of intermediate composition, typed as an L/LL5 with a grain density of ~3530 k gm−3, an average bulk density of 3150 kg m−3 and calculated porosity of ~10%. From noble gas measurements, the cosmic ray exposure age is 25 ± 4 Ma while gas retention ages are all >2 Ga. Short-lived radionuclides and noble gas measurements of the pre-atmospheric size overlap with estimates from infrasound and light curve modeling producing a preferred pre-atmospheric mass of 70–200 kg. The orbit of Golden has a high inclination (23.5°) and is consistent with delivery from the inner main belt. The highest probability (60%) of an origin is from the Hungaria group. We propose that Golden may originate among the background S-type asteroids found interspersed in the Hungaria region. The current collection of 18 L/LL—chondrite orbits shows a strong preference for origins in the inner main belt, suggesting multiple parent bodies may be required to explain the diversity in CRE ages and shock states.

¹Noguchi, Takaaki et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14093]
¹Division of Earth and Planetary Sciences, Kyoto University, Kyoto, Japan
Published by arrangement with John Wiley & Sons

Samples returned from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 mission revealed that Ryugu is composed of materials consistent with CI chondrites and some types of space weathering. We report detailed mineralogy of the fine-grained Ryugu samples allocated to our “Sand” team and report additional space weathering features found on the grains. The dominant mineralogy is composed of a fine-grained mixture of Mg-rich saponite and serpentine, magnetite, pyrrhotite, pentlandite, dolomite, and Fe-bearing magnesite. These grains have mineralogy comparable to that of CI chondrites, showing severe aqueous alteration but lacking ferrihydrite and sulfate. These results are similar to previous works on large Ryugu grains. In addition to the major minerals, we also find many minerals that are rare or have not been reported among CI chondrites. Accessory minerals identified are hydroxyapatite, Mg-Na phosphate, olivine, low-Ca pyroxene, Mg-Al spinel, chromite, manganochromite, eskolaite, ilmenite, cubanite, polydymite, transjordanite, schreibersite, calcite, moissanite, and poorly crystalline phyllosilicate. We also show scanning transmission electron microscope and scanning electron microscope compositional maps and images of some space-weathered grains and severely heated and melted grains. Although our mineralogical results are consistent with that of millimeter-sized grains, the fine-grained fraction is best suited to investigate impact-induced space weathering.

^1,2Gabriel A. Pinto,³Emmanuel Jacquet,⁴Alexandre Corgne,²Felipe Olivares,¹Johan Villeneuve,¹Yves Marrocchi
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.11.012]
¹Université de Lorraine, CNRS, CRPG, UMR 7358, Vandœuvre-lès-Nancy, 54501, France
²INCT, Universidad de Atacama, Copayapu 485, Copiapó, Chile
³Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, 75005 Paris, France
⁴Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile
Copyright Elsevier

Ferromagnesian chondrules present a remarkable dichotomy between reduced (type I) and oxidized (type II) varieties. How these formed, and how they may be related remains contentious. Many type II chondrules, especially in carbonaceous chondrites, contain forsteritic grains in disequilibrium with FeO-rich host olivine grains, which must be relicts of precursor material. In this study, we analyzed the oxygen isotopic composition of magnesian relict and host olivine grains in type II chondrules in CO and CR chondrites. The analyzed Mg-rich relicts are generally more 16O-rich than ferroan olivine (mostly host) grains and plot in the range (in term of chemistry and isotopic composition) of type I chondrules in carbonaceous chondrites. Remarkably, they tend to cluster around the dominant Δ17O peaks of the type I chondrules in their host chondrites, viz. –6 ‰ and –2 ‰ for CO and CR, respectively. With the occurrence of relatively intact type I chondrules within some type II chondrules, this corroborates that local type I chondrules were among the precursors of type II chondrules, and that chondrule formation occurred within the accretion reservoir of the eventual chondrites. This supports the nebular brand of chondrule-forming scenarios. Since not all previous generations of chondrules (or other precursor objects) have been recycled, chondrule formation events must also have been extremely localized.