¹Hannah L.Bercovici,¹Linda T.Elkins-Tanton,¹Joseph G.O’Rourke,²Laura Schaefer
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114976]
¹School of Earth and Space Exploration, ASU, 781 E Terrace Mall Tempe, AZ 85287, USA
²Stanford University, 450 Serra Mall, Stanford, CA 94305, USA
Copyright Elsevier

This study explores the compositions and sizes of metallic cores that result from planetesimals forming from a range of chondritic bulk compositions. Our models examine the influence of starting bulk composition on core size and composition, how oxygen fugacity (fO2), temperature, pressure, and bulk composition affect sulfur partitioning between the core and silicate mantle of planetesimals, and the formation and fate of immiscible sulfur-rich liquid during core solidification. We apply experimentally-derived equations for the sulfur distribution coefficient to the bulk compositions of ordinary chondrites (H,L,LL) and carbonaceous chondrites (CM, CI, CO, CK, CV) under conditions appropriate for melting planetesimals.

The sulfur content of all modeled cores is above 6 wt% S, which is greater than the amount of sulfur needed to form an immiscible sulfide liquid in the presence of other light elements (e.g., C, Si, and/or P). We concluded that early planetesimal cores likely formed either an immiscible sulfide liquid, a eutectic sulfide liquid, or most surprisingly, were composed of mostly monosulfide solid solution, [(Fe, Ni)1-xS].

¹Hiroshi Kimura,²Johannes Markkanen,³Ludmilla Kolokolova,⁴Martin Hilchenbach,¹Koji Wada,¹Yasumasa Kanada,¹Takafumi Matsuia
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114964]
¹Planetary Exploration Research Center (PERC), Chiba Institute of Technology, Tsudanuma 2-17-1, Narashino, Chiba 275-0016, Japan
²Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
³ Planetary Data System Group, Department of Astronomy, Rm. 2337, Computer and Space Science Bldg., University of Maryland, College Park, MD, 20742, USA
⁴ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany
Copyright Elsevier

A well-established constraint on the size of non-porous olivine grains or the porosity of aggregates consisting of small olivine grains from prominent narrow peaks in thermal infrared spectra characteristic of crystalline silicates is reexamined. To thoroughly investigate thermal infrared peaks, we make theoretical argument for the absorption and scattering of light by non-porous, non-spherical olivine particles, which is followed by numerical verification. Our study provides perfectly rational explanations of the physics behind the small-particle effect of emission peaks in the framework of classical electrodynamics and convincing evidence of small-particle’s emission peaks in the literature. While resonant absorption excited by surface roughness on the order of submicrometer scales can be identified even for non-porous olivine particles with a radius of m, it makes only a negligible contribution to thermal infrared spectra of the particles. In contrast, the porosity of non-spherical particles has a significant impact on the strength and wavelength of the peaks, while the resonant absorption excited by an ensemble of small grains takes place at a wavelength different than one expects for surface roughness. We finally reaffirm that twin peaks of olivine in thermal infrared spectra of dust particles in astronomical environments are the intrinsic diagnostic characters of submicrometer-sized small grains and their aggregate particles in fluffy and porous configurations.

¹Marina A. Ivanova,¹Cyril A. Lorenz,²Munir Humayun,²Shuying Yang,³Chi Ma,¹Svetlana N. Teplyakova,⁴Ian A. Franchi,¹Alexander V. Korochantsev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13786]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, 119991 Russia
²National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, 1800 E. Paul Dirac Drive, Tallahassee, Florida, 32310 USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125 USA
⁴Planetary and Space Sciences Research Institute, Open University, Milton Keynes, MK7 6AA UK
Published by arrangement with John Wiley & Sons

The new metal-enriched anomalous chondrite Sierra Gorda 013 (SG 013) contains two different lithologies. Lithology 1 (L1) is represented by anomalous CBa-like chondrite material containing ~80 vol% of Fe,Ni-metal particles and globules up to 6 mm in size; chondrules and clasts of types POP, BO, and SO (up to 5 mm in diameter); rare sulfides; and shock melted silicate–metal areas. It does not contain any fine-grained matrix. Several chondrules contain chromite–pyroxene symplectites. Lithology 2 (L2) has a recrystallized texture with evenly distributed olivine, pyroxene and plagioclase. L2 does not have any chondrules or sulfides, and contains less Fe,Ni- metal (~25 vol%) than L1. Both lithologies contain reduced olivine (Fa2–4) and pyroxene (Fs3.5), similar to CBa chondrites. Similar to CBa, there is no Ni-Co correlation in the SG 013 metal. Rare sulfides in L1 are enriched in V. Chromite was observed in both lithologies. Oxygen isotope compositions of both lithologies are different but in the range of CBa chondrites. Bulk major and trace element geochemistry of nonporphyritic chondrules and bulk siderophile compositions in metal globules of L1 indicate elemental fractionation during formation of metallic and silicate objects with records of the evaporation process: depletion in moderate and volatile elements with the exception of Cr. Bulk geochemistry of porphyritic chondrules of L1 and the silicate portion of L2 is similar and also indicates evaporation processes. The rare Earth element (REE) distribution of L1 chondrules records a very fractionated signature corresponding to possible differentiated precursor material, while the REE pattern of L2 is primitive chondritic. The formation of SG 013 could be explained by collisions of planetesimals producing an impact plume, the precursor material of which could be chondritic and possibly differentiated. Both lithologies were affected by secondary processes: L1 preserved the traces of shock events and partial melting resulting in formation of symplectites in chondrules, melt pockets, and metal–silicate melt between the metal globules; L2 was affected by shock thermal metamorphism (up to 900 °C) resulting in recrystallization.

¹Romain Tartèse,¹Stanley Endley,¹Katherine H. Joy
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13798]
¹Department of Earth and Environmental Sciences, The University of Manchester, Manchester, M13 9PL UK
Published by arrangement with John Wiley & Sons

Impact crater central peaks and peak ring complexes are important exploration targets for future missions to other planetary bodies, because they provide access to material uplifted from lower crustal levels. Material exposed there could also provide chronological constraints on crater formation events. Therefore, it is essential to understand if uplifted peak material preserves the chronological records of igneous and metamorphic protolith crustal rocks, or if such records are reset during impact events. To investigate this issue, we collected shocked gneiss and granite samples from uplifted crystalline basement megablocks in the 24 km diameter Ries impact crater in Germany, which is dated at ~14.8 Ma. Petrographic observations, electron beam imaging, and Raman spectroscopy suggest that these samples record the peak pressures of ~10–15 GPa. In situ U-Pb dating shows that monazite U-Pb systematics have not been affected by the Ries impact, as gneisses and granites yielded monazite U-Pb dates of ~370 and 330 Ma, consistent with known Variscan metamorphic and magmatic events. The U-Pb systematics of some zircon grains yielded U-Pb dates of approximately 5–10 Ma, which is younger than the age of the Ries impact event. These young dates correspond to U-rich metamict domains and may reflect recent Pb loss and/or U-gain during postimpact hydrothermal alteration or weathering. These observations indicate that dating uplifted crystalline material in impact craters on other bodies might provide useful petrological and chronological constraints on the underlying target rocks rather than directly dating impact events, for which sampling impact melt and impact melt-bearing lithologies should remain the primary target.

^1,2Yuan Li,^1,2Yan-Xiang,^1,2LiZhengXu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.027]
¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China
Copyright Elsevier

Geochemical and cosmochemical reservoirs show Cu/Ag variations from 500 to 40000. To understand magmatic Cu–Ag fractionation and origins of such large Cu/Ag variations, we have measured the partition coefficients of Cu and Ag between minerals and silicate melts () relevant for partial melting of the silicate mantles of Earth, Mars, and the Moon. The experiments were conducted at 1–3 GPa, 1300–1600 °C, and oxygen fugacity ∼2–5 log units below the FMQ buffer. The results show that are 0.034–0.109 for olivine, 0.011–0.044 for orthopyroxene, and 0.046–0.092 for clinopyroxene; are 0.003–0.012 for orthopyroxene and 0.037–0.093 for clinopyroxene. These values increase mainly with increasing pressure and are oxygen fugacity-independent. are 0.0005–0.0017 for olivine, which do not show measurable dependence on P–T, oxygen fugacity, or silicate composition. One pair of values are 0.0037 and 0.0004 for garnet, respectively; 0.15 and 0.005 for spinel, respectively. These results indicate that Ag is more incompatible than Cu in all mantle minerals. Our combined with previous sulfide–silicate melt partition coefficients of Cu and Ag imply that although sulfides host large fractions of planetary mantle Cu and Ag, silicate minerals can be also important Cu and Ag reservoirs, particularly when sulfides occur as monosulfide solid solutions. The application of our to various melting models demonstrates that Cu–Ag fractionation occurs during partial melting of the silicate mantles of Earth, Mars, and the Moon; however, the modeled Cu/Ag ratios in basalts agree with their mantle source Cu/Ag ratios within 50% relative. Therefore, the superchondritic but similar Cu/Ag ratios of ∼3000–4000 in mid-ocean ridge basalts, arc basalts, mantle plume-related oceanic island basalts and plateau basalts, and the bulk silicate Earth (BSE) reflect homogeneous distribution of Cu/Ag in Earth’s mantle and limited Cu–Ag fractionation during slab dehydration/melting in subduction zones. However, components with chondritic Cu/Ag ratios (∼600–2300) may exist in the mantle sources of Hawaii oceanic island lavas. The Cu/Ag ratios (∼500–1100) in the Martian basalts and bulk silicate Mars (BSMars) are chondritic, but the Cu/Ag ratio (∼15000–40000) in the bulk silicate Moon (BSMoon) is strongly superchondritic. Such largely different Cu/Ag ratios in different planetary reservoirs cannot be explained by magmatic Cu–Ag fractionation, solar nebular process, or core-formation process. We propose that different degrees of planetary melting and evaporation provide a solution because Ag is more volatile than Cu during silicate melt evaporation. The chondritic Cu/Ag ratios in the BSMars could be explained by limited evaporation of planetesimals that delivered Mars’ moderately volatile elements, and the superchondritic Cu/Ag ratios in the BSE may be due to Earth’s accretion of planetesimals with partial evaporative loss of Cu and Ag. However, high degrees of evaporative Cu and Ag loss during the Moon-formation are required to explain the strongly superchondritic Cu/Ag ratios in the BSMoon. Accordingly, Cu/Ag ratios in the bulk silicate planets may provide new insights into the nature of their building blocks.

¹Anna Barbaro,^2,3Fabrizio Nestola,⁴Lidia Pittarello,⁴Ludovic Ferrière,⁵Mara Murri,⁶Konstantin D. Litasov,²Oliver Christ,¹Matteo Alvaro,¹M. Chiara Domeneghetti
American Mineralogist 107, 377-384 Link to Article [DOI: https://doi.org/10.2138/am-2021-7856]
¹Department of Earth and Environmental Sciences, University of Pavia, Via A. Ferrata 1, I-27100 Pavia, Italy
²Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova, Italy
³Geoscience Institute, Goethe-University Frankfurt, Altenhöferallee 1, 60323 Frankfurt, Germany
⁴Department of Mineralogy and Petrography, Natural History Museum, Burgring 7, 1010 Vienna, Austria
⁵Department of Earth and Environmental Sciences, University of Milano-Bicocca, I-20126 Milano, Italy
⁶Vereshchagin Institute for High Pressure Physics RAS, Troitsk, Moscow, 108840 Russia
Copyright: The Mineralogical Society of America

The formation and shock history of ureilite meteorites, a relatively abundant type of primitive
achondrites, has been debated for decades. For this purpose, the characterization of carbon phases
can provide further information on diamond and graphite formation in ureilites, shedding light on the
origin and history of this meteorite group. In this work, we present X‑ray diffraction and micro‑Raman
spectroscopy analyses performed on diamond and graphite occurring in the ureilite Yamato 74123
(Y-74123). The results show that nano- and microdiamonds coexist with nanographite aggregates.
This, together with the shock-deformation features observed in olivine, such as mosaicism and planar
fractures, suggest that diamond grains formed by a shock event (≥15 GPa) on the ureilitic parent
body (UPB). Our results on Y-74123 are consistent with those obtained on the NWA 7983 ureilite and
further support the hypothesis that the simultaneous formation of nano- and microdiamonds with the
assistance of a Fe-Ni melt catalysis may be related to the heterogeneous propagation and local scat –
tering of the shock wave. Graphite geothermometry revealed an average recorded temperature (Tmax)
of 1314 °C (±120 °C) in agreement with previously estimated crystallization temperatures reported
for graphite in Almahata Sitta ureilite.

^1,2,4Tomohiro Usui,^2,4Kevin Righter,^3,4Charles K. Shearer,⁴John H. Jones
American Mineralogist 107, 357–368 Link to Article [DOI: https://doi.org/10.2138/am-2021-7743]
¹Institute of Space and Astronautical Sciences, Japan Aerospace Exploration Agency, Kanagawa, 252-5210, Japan
²NASA Johnson Space Center, Mailcode XI2, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
³Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A.
⁴Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Society of America

Ni and Co variations in primary martian magmas exhibit anomalous incompatible behavior, which
has remained an unexplained conundrum. Because martian magmas are S-rich, and some trace metals
are reported to have enhanced solubility in S-bearing magmas, we have carried out a series of experi–
ments to evaluate the effect of high-S melts on the olivine/melt partitioning of Ni, Co, Mn, V, and Cr.
Near-liquidus experiments on a synthetic primary martian mantle melt (Yamato-980459 [Y98]) were
completed in a piston-cylinder apparatus at 0.75GPa. Previous studies in S-free systems illustrate that
the partition coefficients for these elements are dependent chiefly on DMg(Ol/melt) (the partition coefficient
defined as wt% Mg in olivine/wt% Mg in melt, a proxy for temperature), and were used to calibrate a
predictive expression that includes the effects of temperature [i.e., DMg(Ol/melt)], melt composition, and
oxygen fugacity. These predictive expressions are then used to isolate any effect in DM olivine/melt
due to dissolved sulfur. The results show that S might have a small effect for Co, but not enough to
change Co partitioning from compatible to incompatible in our experiments. The addition of a sulfur
term to the DCo predictive expressions shows that nearly 8000 ppm of sulfur would be required in the
melt (at liquidus temperature of Y98) for DCo to become <1. These S contents are two times higher
than those of a sulfide-saturated melt at the P–T conditions of a martian mantle source region. Therefore,
the anomalous incompatible behavior observed in these primary magma suites must be due to another
mechanism. High temperature, oxygen fugacity, and diffusion are not viable mechanisms, but magma
mixing, assimilation, or kinetic crystallization effects remain possibilities.

¹B. J. Tkalcec,²P. Tack,²E. De Pauw,²B. Vekemans,³T. Nakamura,⁴J. Garrevoet,⁴G. Falkenberg,²L. Vincze,¹F. E. Brenker
Meteoritics & Planetary Society (in Press) Link to Article [https://doi.org/10.1111/maps.13797]
¹Department of Geosciences, Goethe University Frankfurt, Altenhoeferallee 1, Frankfurt am Main, 60438 Germany
²Department of Chemistry, XMI Research Group, Ghent University, Krijgslaan 281 S12, Ghent, 9000 Belgium
³Department of Earth Science, Tohoku University, Sendai, Miyagi, 980-8578 Japan
⁴Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, Hamburg, 22607 Germany
Published by arrangement with John Wiley & Sons

Reliable identification of chondrules, calcium-aluminum-rich inclusions (CAIs), carbonate grains, and Ca-phosphate grains at depth within untouched, unprepared chondritic samples by a nondestructive analytical method, such as synchrotron X-ray fluorescence (SXRF) computed tomography (CT), is an essential first step before intrusive analytical and sample preparation methods are performed. The detection of a local Ca-enrichment could indicate the presence of such a component, all of which contain Ca as major element and/or Ca-bearing minerals, allowing it to be precisely located at depth within a sample. However, the depth limitation from which Ca-K fluorescence can travel through a chondrite sample (e.g., ∼115 µm through material of 1.5 g cm⁻³) to XRF detectors leaves many Ca-bearing components undetected at deeper depths. In comparison, Sr-K lines travel much greater distances (∼1700 µm) through the same sample density and are, thus, detected from much greater depths. Here, we demonstrate a clear, positive, and preferential correlation between Ca and Sr and conclude that Sr-detection can be used as proxy for the presence of Ca (and, thus, Ca-bearing components) throughout mm-sized samples of carbonaceous chondritic material. This has valuable implications, especially for sample return missions from carbonaceous C-type asteroids, such as Ryugu or Bennu. Reliable localization, identification, and targeted analysis by SXRF of Ca-bearing chondrules, CAIs, and carbonates at depth within untouched, unprepared samples in the initial stages of a multianalysis investigation insures the valuable information they hold of pre- and post-accretion processes in the early solar system is neither corrupted nor destroyed in subsequent processing and analyses.

¹J.N.Connelly,²A.A.Nemchin,³R.E.Merle,⁴J.F.Snape,³M.J.Whitehouse,¹M.Bizzarro
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.026]
¹Centre for Star and Planet Formation, GLOBE Institute, University of Copenhagen, Øster Voldgade, 5-7, DK-1350, Copenhagen, Denmark
²School of Earth and Planetary Sciences (EPS), Curtin University, GPO Box U1987, Perth, WA 6845, Australia
³Department of Earth Sciences, Natural Resources and Sustainable Development, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden
⁴Faculty of Earth and Life Sciences, VU Amsterdam, De Boelelaan 1085,1081 HV Amsterdam, the Netherlands
Copyright Elsevier

Previous isotope studies of lunar samples have demonstrated that volatile loss was an important part of the early history of the Moon. The radiogenic U-Pb system, where Pb has a significantly lower T_50% condensation temperature than U, has the capacity to both recognize and calibrate the extent of volatile loss but this approach has been hindered by terrestrial Pb contamination of samples. We employ a novel method that integrates analyses of individual samples by Ion Microprobe and Thermal Ionization mass spectrometry to correct for ubiquitous common Pb contamination, a method that results in significantly higher estimates for µ-values (²³⁸U/²⁰⁴Pb) than previously reported. Using this method, six of seven samples of low-Ti basaltic meteorites return µ-values between 1900 and 9600, values that are consistent with a re-evaluation of published results that return µ-values of 510-2900 for both low- and high-Ti basalts. While some degree of fractionation during partial melting may increase µ-values, we infer that the source region(s) for the basalts must also have had elevated µ-values by the time the lunar magma ocean solidified. Models to account for the available initial Pb isotopic compositions of lunar basalts in light of timing constraints from thermal modelling imply that their source regions had a µ-value of at least 280, consistent with the elevated µ-values of lunar basalts and that inferred for their sources. Such high µ-values are attributed to the preferential loss of more than 99% of the Pb over U relative to a precursor with a Mars-like composition in the aftermath of the giant impact. Such an extensive loss of Pb is consistent with previously reported losses of other elements with comparable volatility, namely Zn, Rb, Ga and CrO₂. Finally, our modelling of highly-radiogenic lunar Pb isotopes assuming crystallization of the lunar magma ocean over 10’s of millions of years shows that the elevated µ-values allows for, but does not require, a young Moon formation age.

¹Adrian P.Broz,²Joanna Clark,³Brad Sutter,⁴Doug W.Ming,³ValerieTu,⁵Briony Horgan,⁶Lucas C.R.Silva
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114965]
¹Department of Earth Sciences, University of Oregon, Eugene, OR 97405, United States of America
²Geocontrols Systems – Jacobs JETS Contract, NASA Johnson Space Center, Houston, TX 77058, United States of America
³Jacobs JETS Contract, NASA Johnson Space Center, Houston, TX 77058, United States of America
⁴NASA Johnson Space Center, Houston, TX 77058, United States of America
⁵Department of Earth, Atmospheric and Planetary Science, Purdue University, IN, 47907, United States of America
⁶Environmental Studies Program, Department of Geography, University of Oregon, Eugene, OR 97405, United States of America
Copyright Elsevier

Ancient (4.1–3.7-billion-year-old) layered sedimentary rocks on Mars are rich in clay minerals which formed from aqueous alteration of the Martian surface. Many of these sedimentary rocks appear to be composed of vertical sequences of Fe/Mg clay minerals overlain by Al clay minerals that resemble paleosols (ancient, buried soils) from Earth. The types and properties of minerals in paleosols can be used to constrain the environmental conditions during formation to better understand weathering and diagenesis on Mars. This work examines the mineralogy and diagenetic alteration of volcaniclastic paleosols from the Eocene-Oligocene (43–28 Ma) Clarno and John Day Formations in eastern Oregon as a Mars-analog site. Here, paleosols rich in Al phyllosilicates and amorphous colloids overlie paleosols with Fe/Mg smectites that altogether span a sequence of ~ 500 individual profiles across hundreds of meters of vertical stratigraphy. Samples collected from three of these paleosol profiles were analyzed with visible/near-infrared (VNIR) spectroscopy, X-ray diffraction (XRD), and evolved gas analysis (EGA) configured to operate like the SAM-EGA instrument onboard Curiosity Mars Rover. Strongly crystalline Al/Fe dioctahedral phyllosilicates (montmorillonite and nontronite) were the major phases identified in all samples with all methods. Minor phases included the zeolite mineral clinoptilolite, as well as andesine, cristobalite, opal-CT and gypsum. Evolved H₂O was detected in all samples and was consistent with adsorbed water and the dehydroxylation of a dioctahedral phyllosilicate, and differences in H₂O evolutions between montmorillonite and nontronite were readily observable. Detections of hematite and zeolites suggested paleosols were affected by burial reddening and zeolitization, but absence of illite and chlorite suggest that potash metasomatism and other, more severe diagenetic alterations had not occurred. The high clay mineral content of the observed paleosols (up to 95 wt%) may have minimized diagenetic alteration over geological time scales. Martian paleosols rich in Al and Fe smectites may have also resisted severe diagenetic alteration, which is favorable for future in-situ examination. Results from this work can help differentiate paleosols and weathering profiles from other types of sedimentary rocks in the geological record of Mars.