¹Paul H. Warren,²Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13780]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095 USA
²Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri, 63130 USA
Published by arrangement with John Wiley & Sons

We review constraints on the magnitude and possible causes of discrepancies, or at least major disparities, among global and near-global data sets for lunar highland surface composition. When compared with data from other sources, reported mafic mineral abundance results from the Kaguya Spectral Profiler (Kaguya SP) spectral reflectance method for four Apollo 16 soils appear systematically low by a factor of 0.6, or an even more extreme factor (~1/3) if viewed in relation to the soils’ nonglass or CIPW mineralogy. Also, whether evaluated on a global median basis or on the basis of site-by-site comparison (for Apollo 16, Luna 20, and Apollo 17), the compositions found by the Kaguya SP technique show discrepancy, or at least disparity, versus other mafic abundance observations by that same factor of ~1/3. Spectral reflectance does not supply a simple bulk analysis of the target soil. The reflectance mineralogical signal is preponderantly determined by the nonglass fraction, and especially the masswise subordinate 10–20 µm grain size fraction. Literature data show that in anorthositic lunar soil, chemical composition is fractionated, more extremely anorthositic, for the nonglass component compared to the glass component. Also, the grain size fraction (10–20 μm) that most closely matches bulk reflectance has a significantly higher abundance of impact/agglutinitic glass than does the coarser material that dominates the soil mass. The Kaguya SP mafic abundance calibration needs adjustment by a factor of nearly 3 if results are to be interpreted as indicative of the mineralogy of the underlying crust. A claimed detection of several hundred lunar 500 m scale purest anorthosite (PAN; ≥98 vol% plagioclase) locales among millions of spectral reflectance observations is dubious, in part because with large data sets, compositional extremes are inevitably exaggerated as a byproduct of analytical uncertainty. Preponderance of PAN composition is rare among terrestrial layered intrusive anorthosites and is neither required nor expected for the flotation crust of a global magma ocean. Buoyant flotation and compaction would not suffice to yield pure plagioclase unless adcumulus growth was negligible, and trace element contents of ferroan anorthosites show that their mafic silicate components are for the most part of adcumulus, not “trapped melt,” derivation. A PAN-dominated crust would imply a curiously fractionated (low) thorium/aluminum ratio for the crust, an implausibly high mantle/crust Th concentration ratio, and an oddly low Th/Al for the bulk Moon. Remote sensing techniques for planetary regolith composition are not easy to calibrate, particularly near the extremes of composition-space and sensitivity.

^1,2Takafumi Matsui,²Ryota Moriwaki,³Eissa Zidan,¹Tomoko Arai
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13787]
¹Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016 Japan
²Institute for Geo-Cosmology, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016 Japan
³Conservation Center, Grand Egyptian Museum, El Remayah Square, Cairo-Alex. Road, Pyramids, Giza Governorat, Egypt
Published by arrangement with John Wiley & Sons

The Iron Age was the time when people acquired iron processing technology and is generally thought to have begun after 1200 B.C. Some prehistoric iron artifacts made of iron meteorites are dated from the Bronze Age. A nicely preserved meteoritic iron dagger was found in the tomb of King Tutankhamen (1361–1352 B.C.) of ancient Egypt. Yet, its manufacturing method and origin remain unclear. Here, we report nondestructive two-dimensional chemical analyses of the Tutankhamen iron dagger, conducted at the Egyptian Museum of Cairo. Elemental mapping of Ni on the dagger blade surface shows discontinuous banded arrangements in places with “cubic” symmetry and a bandwidth of about 1 mm, suggesting a Widmanstätten pattern. The intermediate Ni content (11.8 ± 0.5 wt%) with the presence of the Widmanstätten pattern implies the source meteorite of the dagger blade to be octahedrite. The randomly distributed sulfur-rich black spots are likely remnants of troilite (FeS) inclusions in iron meteorite. The preserved Widmanstätten pattern and remnant troilite inclusion show that the iron dagger was manufactured by low-temperature (<950 °C) forging. The gold hilt with a few percent of calcium lacking sulfur suggests the use of lime plaster instead of gypsum plaster as an adhesive material for decorations on the hilt. Since the use of lime plaster in Egypt started during the Ptolemaic period (305–30 B.C.), the Ca-bearing gold hilt hints at its foreign origin, possibly from Mitanni, Anatolia, as suggested by one of the Amarna letters saying that an iron dagger with gold hilt was gifted from the king of Mitanni to Amenhotep III, the grandfather of Tutankhamen.

^1,2Andrei A. Shiryaev,³Anton D. Pavlushin,^4,5Alexei V. Pakhnevich,⁶Ekaterina S. Kovalenko,¹Alexei A. Averin,⁷Anna G. Ivanova
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13791]
¹A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Leninsky pr. 31 korp. 4, Moscow, 119071 Russia
²Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow, 119017 Russia
³Diamond and Precious Metal Geology Institute, Siberian Branch of RAS, Lenin pr. 39, Yakutsk, 677000 Russia
⁴Paleontological Institute RAS, Profsoyuznaya str. 123, Moscow, 117997 Russia
⁵The Frank Laboratory of Neutron Physics, JINR, Dubna, 141980 Russia
⁶NRC “Kurchatov Institute,”, Kurchatov square 1, Moscow, 123182 Russia
⁷Shubnikov Institute of Crystallography FSRC “Crystallography and Photonics” RAS, Leninsky pr. 53, Moscow, 119333 Russia
Published by arrangement with John Wiley & Sons

An unusual variety of impact-related diamond from the Popigai impact structure—yakutites—is characterized by complementary methods including optical microscopy, X-ray diffraction, radiography and tomography, infrared, Raman, and luminescence spectroscopy providing structural information at widely different scales. It is shown that relatively large graphite aggregates may be transformed to diamond with preservation of many morphological features. Spectroscopic and X-ray diffraction data indicate that the yakutite matrix represents bulk nanocrystalline diamond. For the first time, features of two-phonon IR absorption spectra of bulk nanocrystalline diamond are interpreted in the framework of phonon dispersion curves. Luminescence spectra of yakutite are dominated by dislocation-related defects. Optical microscopy supported by X-ray diffraction reveals the presence of single crystal diamonds with sizes of up to several tens of microns embedded into nanodiamond matrix. The presence of single crystal grains in impact diamond may be explained by chemical vapor deposition–like growth in a transient cavity and/or a seconds-long compression stage of the impact process due to slow pressure release in a volatile-rich target. For the first time, protogenetic mineral inclusions in yakutites represented by mixed monoclinic and tetragonal ZrO2 are observed. This implies the presence of baddeleyite in target rocks responsible for yakutite formation.

¹Guillaume Siron,¹Kohei Fukuda,²Makoto Kimura,¹Noriko T.Kita
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.010]
¹WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
²National Institute of Polar Research, Meteorite Research Center, Midoricho 10-3, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

Chondrules in ordinary chondrites are considered to form in high density environments, likely related to the evolution of protoplanets and large planetesimals. In order to determine the timing of their formation at high time resolution (≤0.1 Ma), we conducted high precision Al-Mg chronology of 17 porphyritic chondrules from 6 different unequilibrated ordinary chondrites (UOCs) of low petrologic subtypes (3.00-3.05). Detailed petrology, mineralogy, and oxygen isotope ratios of individual chondrules were also obtained that include 10 additional chondrules without Al-Mg ages. Seventeen chondrules for Al-Mg chronology consist of 14 chondrules with plagioclase (An₁-An₈₇) and three chondrules with Na-rich glassy mesostasis, all of which have high ²⁷Al/²⁴Mg ratios (30-3,000). The inferred initial (²⁶Al/²⁷Al)₀ ratios range between (6.5 ± 0.6)×10^–6 to (9.5 ± 1.0)×10^–6, corresponding to chondrule formation ages of 1.74 ± ^0.12/_0.11 Ma to 2.13 ± 0.09 Ma after CAIs, which have a canonical (²⁶Al/²⁷Al)₀ ratio of 5.25×10^–5. Six albite-bearing chondrules (An_<30) show a much more restricted ages range, spanning between 2.00 ± ^0.11/_0.10 Ma and 2.07 ± ^0.11/_0.10 Ma. Including 14 anorthite-bearing chondrules studied previously, chondrules in ordinary chondrites have a restricted range of formation ages from 1.8 Ma to 2.2. Ma after CAIs.

Based on the newly acquired oxygen isotope data and previous high precision studies, chondrules in L and LL chondrites do not show systematic difference in their δ¹⁸O and δ¹⁷O signatures. Majority of plagioclase-bearing chondrules studied for Al-Mg chronology show similar oxygen isotope ratios to those of glass-bearing chondrules. There is no obvious difference in Al-Mg ages of chondrules between L and LL chondrites. Thus, chondrules in L and LL chondrites would have formed in common environments and processes, though they accreted to two separate parent bodies by 2.2 Ma after CAIs, which timing is consistent with the proposed thermal model for ordinary chondrite parent bodies. Onset of chondrule formation at 1.8 Ma after CAIs may be caused by the delay of Jupiter formation or the formation of protoplanets in ordinary chondrite chondrule forming regions if chondrules formed by large scale disk shock or impact jetting of protoplanets. Alternatively, early formed chondrules would not be preserved before 1.8 Ma if chondrules formed by the impacts of molten planetesimals.

^1,2,3Jangmi Han,⁴Changkun Park,¹Adrian J.Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.007]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
²Lunar and Planetary Institute, USRA, 3600 Bay Area Boulevard, Houston, TX 77058, USA
³Astromaterials Research and Exploration Science, NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, USA
⁴Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990, South Korea
Copyright Elsevier

Amoeboid olivine aggregates (AOAs) from the Kainsaz CO3.2 chondrite were analyzed using transmission electron microscopy in order to gain a more complete understanding of thermal metamorphism on the parent body and the role of fluids during metamorphic heating. The Kainsaz AOAs are dominated by strongly zoned, fine-grained, olivine grains (Fa2-31) with heterogeneous Fe enrichments along the grain boundaries, which are interpreted as the result of Fe2+-Mg2+ interdiffusion with the matrix during thermal metamorphism. However, our diffusion calculations show that such AOA olivine zoning and compositions cannot be produced by a simple diffusional exchange during metamorphic heating, unlike chondrule olivine zoning and compositions. In addition, fine-grained ferroan olivine overgrowths occur heterogeneously in crystallographic continuity with olivines on the AOA exteriors. The overgrowths (Fa33-36) are compositionally distinct from the underlying AOA olivines and are not fully equilibrated with the matrix olivines (Fa∼20-55). The ferroan olivine overgrowths likely formed by precipitation from fluids in an epitaxial relationship with forsteritic olivine on the edges of AOAs. Texturally and compositionally diverse chromite grains are also observed along olivine grain boundaries, in olivine grains, and in pore spaces between olivine grains. They share a similar crystallographic orientation relationships with adjacent olivine, suggestive of their formation by exsolution and/or epitaxial growth. Collectively, these observations provide evidence for the mobilization of Fe, Mg, Si, Cr, and Al in the presence of fluids along olivine grain boundaries and into olivine grains during thermal metamorphism. We conclude that in Kainsaz AOAs, the strong zonation development in individual olivine grains and the formation of ferroan olivine overgrowths and chromite grains were a fluid-driven process that occurred at relatively low temperatures (<500℃), during the cooling history of the CO3 chondrite parent body, following the peak of thermal metamorphism.

¹Cocean A.,¹Postolachi C.,^1,2Cocean G.,³Bulai G.,¹Munteanu B.,^1,4Cimpoesu N.,¹Cocean I.,¹Gurlui S.
Applied Sciences 12, 983 Link to Article [DOI 10.3390/app12030983]
¹Faculty of Physics, Alexandru Ioan Cuza University of Iasi, 11 Carol I Bld, Iasi, 700506, Romania
²Rehabilitation Hospital Borsa, 1 Floare de Colt Street, Borsa, 435200, Romania
³Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Department of Exact and Natural Sciences, Institute of Interdisciplinary Research, Alexandru Ioan Cuza University of Iasi, Iasi, 700506, Romania
⁴Faculty of Material Science and Engineering, Gheorghe Asachi Technical University of Iasi, 59A Mangeron Bld, Iasi, 700050, Romania

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¹Seppe Lampe et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.008]
¹Analytical-, Environmental-, and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
Copyright Elsevier

Micrometeorites experience varying degrees of evaporation and mixing with atmospheric oxygen during atmospheric entry. Evaporation due to gas drag heating alters the physicochemical properties of fully melted cosmic spherules (CSs), including the size, chemical and isotopic compositions and is thus expressed in its chemical and isotopic signatures. However, the extent of evaporation and atmospheric mixing in CSs often remains unclear, leading to uncertainties in precursor body identification and statistics. Several studies have previously estimated the extent of evaporation based on the contents of major refractory elements Ca and Al in combination with the determined Fe/Si atomic ratios. Similarly, attempts have been made to design classification schemes based on isotopic variations. However, a full integration of any previously defined chemical classification schemes with the observed isotopic variability has not yet been successful. As evaporation can lead to both chemical and isotope fractionation, it is important to verify whether the estimated degrees of evaporation based on chemical and isotopic proxies converge. Here, we have analysed the major and trace element compositions of 57 chondritic (mostly V-type) CSs, along with their Fe isotope ratios. The chemical (Zn, Na, K or CaO and Al2O3 concentrations) and δ56Fe isotope fractionation measured in these particles show no correlation. The interpretation of these results is twofold: (i) isotopic and chemical fractionation are governed by distinct processes or (ii) the proxies selected for chemical and isotope fractionation are inadequate. While the initial Fe isotopic ratios of chondrites are constrained within a relatively narrow range (0.005 ± 0.008‰ δ56Fe), the chemical compositions of CSs display larger variability. Cosmic spherules are thus often not chemically representative of their precursor bodies, due to their small size. As oxygen isotopes are commonly used to refine the precursor bodies of meteorites, triple oxygen isotope ratios were measured in thirty-seven of the characterized CSs. Based on the relationship between δ18O and δ57Fe, the evaporation effect on the O isotope system can be calculated, which allows for a more accurate parent body determination. Using this correction method, two ‘Group 4’ spherules with strongly variable degrees of isotope fractionation (δ56Fe of ∼1.0‰ and 29.1‰, respectively) could be distinguished. Furthermore, it was observed that all CSs that probably have a OC-like heritage underwent roughly the same degree of atmospheric mixing (∼8‰ δ18O). This highlights the potential of including Fe isotope measurements to the regular methodologies applied to CS studies.

^1,2Tim Cunningham,^1,2Peter J. Wheatley,^1,2Pier-Emmanuel Tremblay,^1,2Boris T. Gänsicke,³George W. King,^4,5Odette Toloza,^1,2Dimitri Veras
Nature 602, 219-222 Link to Areticle [DOI https://doi.org/10.1038/s41586-021-04300-w]
¹Department of Physics, The University of Warwick, Coventry, UK
²Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK
³Department of Astronomy, University of Michigan, Ann Arbor, MI, USA
⁴Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso, Chile
⁵Millennium Nucleus for Planet Formation (NPF), Valparaíso, Chile

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¹Keisuke Fukushi,^1,2Yasuhito Sekine,³Elizabeth B.Rampe
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.005]
¹Institute of Nature and Environmental Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192 Japan
²Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 Japan
³Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX77058, USA
Copyright Elsevier

Mars once possessed liquid water on its surface. In investigations of aqueous conditions on early Mars, the Mars Science Laboratory rover Curiosity has provided mineralogical and geochemical data from lacustrine sediments of Gale Crater, site of a former lake. Recently, the top-down method for quantitative reconstruction of the chemical parameters of ancient pore water, based on exchangeable cation compositions in smectite and secondary minerals, was developed and applied to the Yellowknife Bay sediments in Gale Crater. Here we report the application of this method to lacustrine sediment from the Quela drill site in Gale Crater, in the Karasburg member of the Murray formation. The results show that the final pore water to interact with the sediments had the following chemistry: pH = 3.6–5.6, Eh > 0.22 V, molality of Na ({Na}) = 0.14–2.2 mol/kg, {K} = 0.0080–0.31 mol/kg, {Ca} = 0.021–0.21 mol/kg, {Mg} < 0.14 mol/kg, {Fe(II)} < 0.063 mol/kg, {Cl} = 0.096–2.6 mol/kg and {SO4} = 0.048–0.33 mol/kg. At two adjacent drill sites (Marimba and Sebina), the comparable mineral assemblages and smectite interlayer compositions imply that they have water chemistry similar to that of the Quela sediment. The inferred pore water was undersaturated with respect to halite by an order of magnitude, although the sediment contains halite. This suggests that the final water in the Quela sediment disappeared by freezing and sublimation rather than evaporation. One interpretation of the high Na and Cl concentrations of the final pore water at Quela is that the sediment was deposited in an arid climate at around 3.5 Ga. The high salinity of the final pore water at Quela relative to that at Yellowknife Bay suggests that climate may have shifted from semi-arid when the Yellowknife Bay formation was deposited to arid when the Karasburg member was deposited. Alternatively, the high salinity at Quela suggests that the post-depositional fluids at 2–3 Ga was enriched in Na. In contrast to low Na in the post-depositional fluids in the underlying Yellowknife Bay, the high salinity of the post-depositional fluids of the Quela suggests different origin and/or timing of the re-wetting events between these two sites. The acidic pH and high Eh suggest that the Quela sediment was intensively affected by oxidizing and acidic post-depositional fluids. The pH of the final pore water would not have allowed the preservation of Ca and Mg carbonates under attainable CO2 partial pressures, which is consistent with the scenario of carbonate dissolution by acidic post-depositional fluids on Mars.

¹Bidong Zhang,²Nancy L.Chabot,^1,3Alan E.Rubin⁴Munir Humayun,⁵Joseph S.Boesenberg,⁶Deonvan Niekerk
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.004]
¹Department of Earth, Planetary & Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
²Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
³Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, ME 04217, USA
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL 32310, USA
⁵Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
⁶Department of Geology, Rhodes University, Makhanda 6140, South Africa
Copyright Elsevier

Group IIIF was established as a magmatic iron-meteorite group based on similar Ga and Ge abundances, unusually high Ga/Ge ratios, and the IIIAB-like interelement trends in its members; recent Mo and Ru isotopic data indicate that three of its members exhibit the isotopic signature of carbonaceous-chondrite (CC) irons. Here we report the elemental chemistry of this group and model its crystallization history. Included are new elemental data for IIIF irons acquired by both instrumental neutron activation analysis (INAA) and laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). A fractional-crystallization model was used to evaluate the IIIF compositional trends for 19 elements and was unable to explain the observed fractionation trends for several key elements (Co, Ga, Ge). In particular, the inability of this model to match Co in the IIIF irons is striking because (1) group IIIF has the widest Co variation among all magmatic iron groups and (2) none of the tested initial S contents (0−20 wt.%) explains both the wide Co variation and steep Co-As slope. Attempts to fit subsets of the IIIF irons were also unsuccessful. In addition, group IIIF has the greatest variety of structural classes and kamacite bandwidths among all established magmatic iron groups. If the IIIF irons constitute a coherent group, they were derived from a parent body that experienced more complex processes than simple fractional crystallization of the core.

The Zinder and Northwest Africa (NWA) 1911 pyroxene-bearing pallasites were recently suggested to be related to group IIIF based on their Ga and Ge contents, and we completed a petrographic study of the pallasite silicates and LA-ICP-MS analyses of their metal fractions. The two pallasites are related to one another: they have nearly identical mineralogical, elemental and O-isotopic compositions in their silicates and metals. Their metallic compositions resemble those of the IIIF irons Moonbi, St. Genevieve County, and Cerro del Inca, but their O-isotopic compositions resemble those of non-carbonaceous (NC) achondrites. Additional isotopic measurements are needed to test the potential genetic relationship to group IIIF.