¹Emily M. Chiappe,¹Richard D. Ash,²Arto Luttinen,³Sari Lukkari,³Jukka Kuva,⁴Connor D. Hilton,¹Richard J. Walker
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14095]
¹Department of Geology, University of Maryland, College Park, Maryland, USA
²Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland
³Geological Survey of Finland, Espoo, Finland
⁴Pacific Northwest National Laboratory, Richland, Washington, USA
Published by arrangement with John Wiley & Sons

The meteorite Lieksa was found in 2017 in Löpönvaara, Finland, and later donated to the Finnish Museum of Natural History. Here, we report siderophile element concentrations, genetic isotopic data, and a metal–silicate segregation age for the meteorite. The ~280 g Lieksa is ~80% metal and ~20% silicate and oxide inclusions by volume, with the inclusions consisting primarily of Fe-rich olivine. Due to Lieksa’s silicate content, coupled with a texture characterized by metal enclosing the silicates, it has been classified as a pallasite. Lieksa’s olivine and bulk chemical characteristics are distinct from those of the known pallasite and iron meteorite groups, consistent with its classification as ungrouped. The meteorite exhibits a flat, chondrite-normalized highly siderophile element pattern, consistent with an origin as an early crystallization product from a metallic melt with chondritic relative abundances. Molybdenum, Ru, and 183W isotopic data indicate that Lieksa formed in the non-carbonaceous (NC) domain of the solar nebula. Radiogenic 182W abundances for Lieksa yield a model metal–silicate segregation age of 1.5 ± 0.8 Myr after calcium-aluminum-rich inclusion formation, which is within the range established for other NC-type pallasite and iron meteorite parent bodies.

¹Su, Bin,^1,3Zhang, Di,^1,3Chen, Yi,²Yang, Wei¹Mao, Qian,¹Li, Xian-Hua,¹Wu, Fu-Yuan
Science Advances 68, 1918-1927 Link to Article [DOI 10.1016/j.scib.2023.07.020]
¹State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
²Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China

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¹Ji, Jie,¹Liu, Yafang,¹Yang, Xu,²Zhang, Weiwei,³Xiao, Tao,⁴Sun, Jing,²Jiang, Shengyuan
Advances in Space Research 72, 3357-3375 Link to Article [DOI 10.1016/j.asr.2023.05.021]
¹Beijing Institute of Spacecraft System Engineering, Beijing, 100094, China
²State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, China
³Institute of Remote Sensing Satellite, China Academy of Space Technology, Beijing, 100094, China
⁴China Satellite Communications Co. Ltd, Beijing, 100190, China

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^1,2Venkateswara Rao Manga,^1,2Thomas J. Zega
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.11.001]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ
²Department of Materials Science and Engineering, University of Arizona, Tucson, AZ
Copyright Elsevier

Ultrarefractory (UR) condensates found in refractory inclusions in chondrites contain records of the early nebular thermochemistry that prevailed in the high-temperature region close to the protosun. Recent reports of the UR phases such as allendeite (Sc4Zr3O12), tazheranite ((Zr,Ti,Ca)O2-x), and kangite ((Sc,Ti,Al,Zr,Mg,Ca,□)2O3) imply, respectively, nebular condensation temperatures and origins higher than and inward of those previously deduced from calcium-aluminum-rich inclusions. However, knowledge gaps on their thermochemistry have precluded a quantitative understanding of temperatures and chemical pathways that led to their origins in the early solar protoplanetary disk. Here we use density functional theory to determine the thermochemistry of these materials for the first time. We find that allendeite is a stable phase under equilibrium conditions with its condensation temperature (1643 K at 10-4 bar) in the same range as that of nominal hibonite (CaAl12O19, 1637 K at 10-4 bar). Among the UR oxides, tetragonal ZrO2 exhibits the highest condensation temperature (1739 K at 10-4 bar) and potentially reveals the high-temperature limits at which solid dust could have survived in the inner region of the disk. In comparison, we find that pure cubic ZrO2 does not form from a cooling gas of solar composition undergoing equilibrium condensation. Similarly, we find that the stoichiometric endmember of kangite, Sc2O3 does not condense under equilibrium conditions, and moreover, the role of Ti and Zr as solutes is crucial to modeling its stability and origins.

¹A. Pommier,^1,2M.J. Tauber,^1,3H. Pirotte,¹G.D. Cody,¹A. Steele,¹E.S. Bullock,³B. Charlier,¹B.O. Mysen
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.10.027]
¹Carnegie Institution for Science, Earth and Planets Laboratory, Washington, DC 20015, USA
²University of California San Diego, Department of Chemistry and Biochemistry, La Jolla, CA 92093, USA
³University of Liège, Department of Geology, Sart Tilman, Belgium
Copyright Elsevier

Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental for modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S up to 5 wt.%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700-750 K, and for temperatures up to 970 K Ea decreases (0.35-0.68 eV) and the conductivities of the samples converge (∼5-8 ×10-3 S/m). At Tquench, the melt fraction is 50-70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt.% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, a characteristic that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca-S or Mg-S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions.

¹Tarryn Aucamp,¹Geoffrey H. Howarth,¹Chad J. Peel,²Gelu Costin,³James M. D. Day,¹Petrus le Roux,⁴James M. Scott,⁵Ansgar Greshake,⁶Rainer Bartoschewitz
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14090]
¹Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa
²Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, Texas, USA
³Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
⁴Department of Geology, University of Otago, Dunedin, New Zealand
⁵Institut für Mineralogie, Museum für Naturkunde, Humboldt-Universität zu Berlin, Berlin, Germany
⁶Bartoschewitz Meteorite Laboratory, Gifhorn, Germany
Published by arrangement with John Wiley & Sons

The Dar al Gani (DaG) olivine-phyric shergottites share mineralogical and geochemical characteristics, which confirm that these meteorites are derived from a single source. Bulk trace elements (La/Yb—0.12), in situ maskelynite 87Sr/86Sr (~0.7014) and redox estimates (FMQ ~ −2) indicate derivation from a depleted, reduced mantle reservoir; identical to all ~470 Ma shergottites ejected at 1.1 Ma. The DaG shergottites have been variably affected by terrestrial alteration, which precipitated carbonate along fractures and modified bulk-rock fluid mobile (e.g., Ba) elements. Nonetheless, sufficient data are available to construct a multi-stage formation model for the DaG shergottites and other 1.1 Ma ejection-paired shergottites that erupted at ~470 Ma. First, partial melting of a depleted mantle source occurred at 1540 ± 20°C and 1.2 ± 0.1 GPa, equivalent to > ~100 km depth. Then, initial crystallization in a staging chamber at ~85 km depth at the crust–mantle boundary took place, followed by magma evolution and variable incorporation of antecrystic olivine ± orthopyroxene. Subsequently, crystallization of olivine phenocrysts and re-equilibration of olivine antecrysts occurred within an ascending magma. Finally, magmas with variable crystal loads erupted at the surface, where varied cooling rates produced a range of groundmass textures. This model is similar to picritic flood basalt magmas erupted on Earth.

^1,2Qian Yuan et al. (>10)
Nature 623, 95-99 Link to Article [DOI https://doi.org/10.1038/s41586-023-06589-1]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
²Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA

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¹Marina Martínez,^1,2Charles K. Shearer,¹Adrian J. Brearley
American Mineralogist 108, 2024-2042 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P2024.pdf]
¹Department of Earth & Planetary Sciences, MSC03-2040
²University of New Mexico, Albuquerque, New Mexico 87131, U.
Copyright: The Mineralogical Society of America

The microstructures of selected F-, Cl-, and OH-bearing martian apatite grains, two in Northwest
Africa (NWA) 998 (cumulus apatites, embedded in pyroxene) and a set of four in Nakhla (intercumulus
apatites), were studied by focused ion beam–transmission electron microscopy (FIB-TEM) techniques.
Our results show that the nanostructure of martian apatite is characterized by a domain structure at
the 5–10 nm scale defined by undulous lattice fringes and slight differences in contrast, indicative
of localized elastic strain within the lattices and misorientations in the crystal. The domain structure
records a primary post-magmatic signature formed during initial subsolidus cooling (T <800 °C), in which halogens clustered by phase separation (exsolution), but overall preserved continuity in the crystalline structure. Northwest Africa 998 apatites, with average Cl/F ratios of 1.26 and 2.11, show higher undulosity of the lattice fringes and more differences in contrast than Nakhla apatites (average Cl/F = 4.23), suggesting that when Cl/F is close to 1, there is more strain in the structure. Vacancies likely played a key role stabilizing these ternary apatites that otherwise would be immiscible. Apatites in Nakhla show larger variations in halogen and rare-earth element (REE) contents within and between grains that are only a few micrometers apart, consistent with growth under disequilibrium conditions and crystallization in open systems. Nakhla apatite preserves chemical zonation, where F, REEs, Si, and Fe are higher in the core and Cl increases toward the outer layers of the crystal. There is no evidence of subsolidus ionic diffusion or post-magmatic fluid interactions that affected bulk apatite compositions in NWA 998 or Nakhla. The observed zonation is consistent with crystallization from a late-stage melt that became Cl-enriched, and assimilation of volatile-rich crustal sediments is the most plausible mechanism for the observed zonation. This work has broader implications for interpreting the chemistry of apatite in other planetary systems.

¹Kaushik Mitra¹,^2,3Jeffrey G. Catalano,¹Yatharth Bahl,¹Joel A. Hurowitz
Earth and Planetary Science 624, 118464 Link to Article [https://doi.org/10.1016/j.epsl.2023.118464]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY 11727 USA
²Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130 USA
³McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130 USA
Copyright Elsevier

Sulfate salts are abundant, widespread, and temporally distributed on the surface of Mars. Several processes, including sulfide weathering, have been proposed to explain the formation and accumulation of oxidized iron(III) hydroxysulfate (e.g., jarosite) in Martian sediments. Oxidative weathering of iron sulfide minerals (like pyrite and pyrrhotite) could explain the presence of sulfate as well as the relative absence of sulfide minerals in Martian sediments. However, the effectiveness of oxyhalogen compounds, plausible oxidants present on Mars, to weather iron sulfides remain unknown. Here we investigate the oxidative weathering of iron sulfide minerals, pyrite and pyrrhotite, by chlorate and bromate in Mars-relevant fluids. Our results demonstrate that both oxyhalogen species readily oxidize iron sulfides and produce an alteration assemblage comprised of elemental sulfur, Fe(III) (oxyhydr)oxide (magnetite, goethite, and lepidocrocite), and Fe(III) hydroxysulfates (jarosite and schwertmannite). The mineral products depend strongly on the type of sulfide, oxidant, and initial solution pH. Owing to their abundance and highly reactive nature, oxyhalogen brines could be important Fe(III) hydroxysulfate-forming reagents on early and modern Mars and substantially impact the survivability of sulfide minerals at the Martian surface. Additionally, sulfide bearing units might serve as indicators of minimal post-depositional alteration. Oxyhalogens may be responsible for the loss of magmatic sulfides in surface materials given the prevalence of oxyhalogen brines and the reactivity of the sulfides.