¹Kared, R.,²Moine, B.N.,¹Seddiki, A.,²Cottin, J.Y.,³Greenwood, R.C.,³Franchi, I.A.
Arabian Journal of Earth Sciences 12, 442 Link to Article [DOI: 10.1007/s12517-019-4604-9]
¹Laboratoire Géoressources et Risques Naturels (GEOREN); Oran2 University, BP: 1510, Oran, 31000, Algeria
²Magmas & Volcanoes Laboratory UMR6524 CNRS, Lyon University, UJM, Saint-Etienne, France
³Planetary and Space Sciences, Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom

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¹E. V. Petrova,¹V. I. Grokhovsky,²T. Kohout,¹R. F. Muftakhetdinova,¹G. A. Yakovlev
Geochemistry International 57, 923-930 Link to Article [DOI https://doi.org/10.1134/S0016702919080081]
¹Ural Federal University, Institute of Physics and Technology, Yekaterinburg, Russia
²University of Helsinki, Faculty of Science, Helsinki, Finland

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¹C.Lorenz,¹M.Ivanova,²A.Krot,³V.Shuvalov
Geochemistry (Chemie der Erde) (In Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.07.005]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin St. 19, Moscow, 119991, Russia
²University of Hawai‘i at Mānoa, 1680 East-West Road, Honolulu, HI, 96822, USA
³Institute for Dynamics of Geosphere, Russian Academy of Sciences, Moscow, Russia
Copyright Elsevier

Calcium-aluminum-rich inclusions (CAIs) are the oldest Solar System solids dated that formed by evaporation, condensation, aggregation and, sometimes, melting processes near the protoSun, and were subsequently dispersed throughout the protoplanetary disk by still poorly-understood mechanism(s). Here we report on the discovery of disk- and bowl-shaped centimeter-sized igneous CAIs in CV (Vigarano type) carbonaceous chondrites. Igneous CAIs of these shapes are not expected for crystallization of melt droplets in a low gravity field of the protoplanetary disk. We have tested several models for the formation of disk- and bowl-shaped igneous CAIs including: collision, aerodynamic deformation and shock flattening. We conclude that these CAIs resulted from aerodynamic deformation of CAI-like melt droplets and propose the following multistage formation scenario: (1) nearly complete melting and acceleration of CAIs at <30 km/s in the CAI-forming region having approximately solar dust/gas ratio; (2) aerodynamic deformation, ablation, deceleration, solidification at ˜30–40 K/min, Wark-Lovering rims formation, and deceleration of the CAIs entering a dust-rich inner disk wall; (3) radial drift of the solidified deformed CAIs towards the Sun; (4) heating and partial melting of the deformed CAIs by solar radiation that preserve their morphology; (5) cooling and crystallization of CAIs at ˜2 K/h; (5) radial transport of CAIs from their formation region to the outer disk.

^1,2,3Alexander N.Krot,¹Kazuhide Nagashima,⁴Steven B.Simon,⁵Chi Ma,⁶Harold C.Connolly Jr.,¹Gary R.Huss,^7,8,9Andrew M.Davis,³MartinBizzarro
Geochemistry (Chemie der Erde)(In Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.08.001]
¹School of Ocean, Earth Science and Technology, Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, USA
²Geoscience Institute/Mineralogy, Goethe University Frankfurt, Germany
³Centre for Star and Planet Formation, University of Copenhagen, Denmark
⁴Institute of Meteoritics, University of New Mexico, USA
⁵Division of Geological and Planetary Sciences, California Institute of Technology, USA
⁶Department of Geology, School of Earth and Environment, Rowan University, USA
⁷Department of the Geophysical Sciences, The University of Chicago, USA
⁸Enrico Fermi Institute, The University of Chicago, USA
⁹Chicago Center for Cosmochemistry, USA
Copyright Elsevier

Grossite (CaAl₄O₇) is one of the one of the first minerals predicted to condense from a gas of solar composition, and therefore could have recorded isotopic compositions of reservoirs during the earliest stages of the Solar System evolution. Grossite-bearing Ca,Al-rich inclusions (CAIs) are a relatively rare type of refractory inclusions in most carbonaceous chondrite groups, except CHs, where they are dominant. We report new and summarize the existing data on the mineralogy, petrography, oxygen and aluminum-magnesium isotope systematics of grossite-bearing CAIs from the CR, CH, CB, CM, CO, and CV carbonaceous chondrites. Grossite-bearing CAIs from unmetamorphosed (petrologic type 2―3.0) carbonaceous chondrites preserved evidence for heterogeneous distribution of ²⁶Al in the protoplanetary disk. The inferred initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] in grossite-bearing CAIs is generally bimodal, ˜0 and ˜5×10^‒5; the intermediate values are rare. CH and CB chondrites are the only groups where vast majority of grossite-bearing CAIs lacks resolvable excess of radiogenic ²⁶Mg. Grossite-bearing CAIs with approximately the canonical (²⁶Al/²⁷Al)₀ of ˜5×10^‒5 are dominant in other chondrite groups. Most grossite-bearing CAIs in type 2‒3.0 carbonaceous chondrites have uniform solar-like O-isotope compositions (Δ¹⁷O ˜ ‒24±2‰). Grossite-bearing CAIs surrounded by Wark-Lovering rims in CH chondrites are also isotopically uniform, but show a large range of Δ¹⁷O, from ˜ ‒40‰ to ˜ ‒5‰, suggesting an early generation of gaseous reservoirs with different oxygen-isotope compositions in the protoplanetary disk. Igneous grossite-bearing CAIs surrounded by igneous rims of ±melilite, Al-diopside, and Ca-rich forsterite, found only in CB and CH chondrites, have uniform ¹⁶O-depleted compositions (Δ¹⁷O ˜ ‒14‰ to ‒5‰). These CAIs appear to have experienced complete melting and incomplete O-isotope exchange with a ¹⁶O-poor (Δ¹⁷O ˜ ‒2‰) gas in the CB impact plume generated about 5 Ma after CV CAIs. Grossite-bearing CAIs in metamorphosed (petrologic type >3.0) CO and CV chondrites have heterogeneous Δ¹⁷O resulted from mineralogically-controlled isotope exchange with a ¹⁶O-poor (Δ¹⁷O ˜ ‒2 to 0‰) aqueous fluid on the CO and CV parent asteroids 3‒5 Ma after CV CAIs. This exchange affected grossite, krotite, melilite, and perovskite; corundum, hibonite, spinel, diopside, forsterite, and enstatite preserved their initial O-isotope compositions. The internal ²⁶Al-²⁶Mg isochrons in grossite-bearing CAIs from weakly-metamorphosed CO and CV chondrites were not disturbed during this oxygen-isotope exchange.

HCCJr is grateful to Klaus Keil for all his sound profession counsel and collegial friendship over the years. He has always been willing to talk and has the generous nature of listening and sharing his thoughts freely and constructively. Professor Klaus Keil has been a mentor to and played a key role in the careers of three of the authors of this paper (ANK, KN, and GRH). He has also influenced the careers of the other authors and most of the people who have worked on meteorites over the past 50+ years. We therefore dedicate this paper to Professor Keil and present it in this Special Issue of Geochemistry.

^1,2A.N.Krot,²C.Ma,¹K.Nagashima,^4,5,6A.M.Davis,³J.R.Beckett,⁷S.B.Simon,⁸M.Komatsu,⁹T.J.Fagan,²F.Brenker,¹⁰M.A.Ivanova,¹¹A.Bischoff
Geochemistry (Chemie der Erde) (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.07.001]
¹Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, 1680 East-West Road, Honolulu, HI 96822, USA
²Geoscience Institute, Goethe University, 60438 Frankfurt am Main, Germany
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena CA 91125, USA
⁴Department of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637, USA
⁵Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, USA
⁶Chicago Center for Cosmochemistry, Chicago, IL 60637, USA
⁷Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, USA
⁸The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193 Japan
⁹Earth Sciences Department, Waseda University, Shinjuku-ku, Tokyo 169-8050, Japan
¹⁰Vernadsky Institute of Geochemistry of Russian Academy of Sciences, Kosygin St. 19, Moscow 119991, Russia
¹¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
Copyright Elsevier

We report on the mineralogy, petrography, and in situ oxygen isotopic composition of twenty-five ultrarefractory calcium-aluminum-rich inclusions (UR CAIs) in CM2, CR2, CH3.0, CV3.1―3.6, CO3.0―3.6, MAC 88107 (CO3.1-like), and Acfer 094 (C3.0 ungrouped) carbonaceous chondrites. The UR CAIs studied are typically small, < 100 µm in size, and contain, sometimes dominated by, Zr-, Sc-, and Y-rich minerals, including allendeite (Sc4Zr3O12), and an unnamed ((Ti,Mg,Sc,Al)3O5) mineral, davisite (CaScAlSiO6), eringaite (Ca3(Sc,Y,Ti)2Si3O12), kangite ((Sc,Ti,Al,Zr,Mg,Ca,□)2O3), lakargiite (CaZrO3), warkite (Ca2Sc6Al6O20), panguite ((Ti,Al,Sc,Mg,Zr,Ca)1.8O3), Y-rich perovskite ((Ca,Y)TiO3), tazheranite ((Zr,Ti,Ca)O2―x), thortveitite (Sc2Si2O7), zirconolite (orthorhombic CaZrTi2O7), and zirkelite (cubic CaZrTi2O7). These minerals are often associated with 50―200 nm-sized nuggets of platinum group elements. The UR CAIs occur as: (i) individual irregularly-shaped, nodular-like inclusions; (ii) constituents of unmelted refractory inclusions – amoeboid olivine aggregates (AOAs) and Fluffy Type A CAIs; (iii) relict inclusions in coarse-grained igneous CAIs (forsterite-bearing Type Bs and compact Type As); and (iv) relict inclusions in chondrules. Most UR CAIs, except for relict inclusions, are surrounded by single or multilayered Wark-Lovering rims composed of Sc-rich clinopyroxene, ±eringaite, Al-diopside, and ±forsterite. Most of UR CAIs in carbonaceous chondrites of petrologic types 2―3.0 are uniformly 16O-rich (Δ17O ˜ ―23‰), except for one CH UR CAI, which is uniformly 16O-depleted (Δ 17O ˜ ―5‰). Two UR CAIs in Murchison have heterogeneous Δ17O. These include: an intergrowth of corundum (˜ ‒24‰) and (Ti,Mg,Sc,Al)3O5 (˜ 0‰), and a thortveitite-bearing CAI (˜ ‒20 to ˜ ‒5‰); the latter apparently experienced incomplete melting during chondrule formation. In contrast, most UR CAIs in metamorphosed chondrites are isotopically heterogeneous (Δ17O ranges from ˜ ―23‰ to ˜ ―2‰), with Zr- and Sc-rich oxides and silicates, melilite and perovskite being 16O-depleted to various degrees relative to uniformly 16O-rich (Δ17O ˜ ―23‰) hibonite, spinel, Al-diopside, and forsterite. We conclude that UR CAIs formed by evaporation/condensation, aggregation and, in some cases, melting processes in a 16O-rich gas of approximately solar composition in the CAI-forming region(s), most likely near the protoSun, and were subsequently dispersed throughout the protoplanetary disk. One of the CH UR CAIs formed in an 16O-depleted gaseous reservoir providing an evidence for large variations in Δ17O of the nebular gas in the CH CAIs-forming region. Subsequently some UR CAIs experienced oxygen isotopic exchange during melting in 16O-depleted regions of the disk, most likely during the epoch of chondrule formation. In addition, UR CAIs in metamorphosed CO and CV chondrites, and, possibly, the corundum-(Ti,Mg,Sc,Al)3O5 intergrowth in Murchison experienced O-isotope exchange with aqueous fluids on the CO, CV, and CM chondrite parent asteroids. Thus, both nebular and planetary exchange with 16O-depleted reservoirs occurred.

¹Nadia Vogel,^1,2Veronika S.Heber,³Peter Bochsler,⁴Donald S.Burnett,¹Colin Maden,¹Rainer Wieler
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.08.007]
¹ETH Zürich, Institute for Geochemistry and Petrology, Department of Earth Sciences, Clausiusstrasse 25, CH-8092 Zürich, Switzerland
²Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
³Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
⁴California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA 91125, USA
Copyright Elsevier

We discuss elemental abundances of noble gases in targets exposed to the solar wind (SW) onboard the “Genesis” mission during the three different SW “regimes”: “Slow” (interstream, IS) wind, “Fast” (coronal hole, CH) wind and solar wind related to coronal mass ejections (CME). To this end we first present new Ar, Kr, and Xe elemental abundance data in Si targets sampling the different regimes. We also discuss He, Ne, and Ar elemental and isotopic abundances obtained on Genesis regime targets partly published previously. Average Kr/Ar ratios for all three regimes are identical to each other within their uncertainties of about 1% with one exception: the Fast SW has a 12% lower Xe/Ar ratio than do the other two regimes. In contrast, the He/Ar and Ne/Ar ratios in the CME targets are higher by more than 20% and 10%, respectively, than the corresponding Fast and Slow SW values, which among themselves vary by no more than 2-4%.
Earlier observations on lunar samples and Genesis targets sampling bulk SW wind had shown that Xe, with a first ionisation potential (FIP) of ∼12 eV, is enriched by about a factor of two in the bulk solar wind over Ar and Kr compared to photospheric abundances, similar to many “low FIP” elements with a FIP less than ∼10 eV. This behaviour of the “high FIP” element Xe was not easily explained, also because it has a Coulomb drag factor suggesting a relatively inefficient feeding into the SW acceleration region and hence a depletion relative to other high FIP elements such as Kr and Ar. The about 12% lower enrichment of Xe in Genesis’ Fast SW regime observed here is, however, in line with the hypothesis that the depletion of Xe in the SW due to the Coulomb drag effect is overcompensated as a result of the relatively short ionisation time of Xe in the ion-neutral separation region in the solar chromosphere. We will also discuss the rather surprising fact that He and Ne in CME targets are quite substantially enriched (by 20% and 10%, respectively) relative to the other solar wind regimes, but that this enrichment is not accompanied by an isotopic fractionation. The Ne isotopic data in CMEs are consistent with a previous hypothesis that isotopic fractionation in the solar wind is mass-dependent.

¹Michael Schindler,¹Sophie Michel,²Daniel Batcheldor,^3,4Michael F.Hochella
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.08.008]
¹Department of Earth Sciences, 935 Ramsey Lake Road, Laurentian University, Sudbury, ON, Canada, P3E2C6
²Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL, 32901, USA
³Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA
⁴Subsurface Science and Technology Group, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
Copyright Elsevier

Iron(hydr)oxides are one of the most important constituents of regoliths and soils derived from volcanic rocks both on Earth and Mars, often giving them their characteristic red color. This study deciphers for the first time an underlying mechanism for the formation of Fe-(hydr)oxides in a regolith which can occur during the weathering of basaltic glass; Fe-(hydr)oxides are prominent alteration products of regoliths under low water/rock ratios. An excellent example of these conditions is the early stage of basaltic glass weathering in the Martian regolith simulant JSC MARS-1A. In this study, a combination of focused ion beam technology and analytic transmission electron microscopy is employed in order to characterize basaltic glass weathering down to the nanometer level. Our results show that the formation of Fe-(hydr)oxide phases such as ferrihydrite, magnetite/maghemite and hematite during alteration of basaltic glass is based on complex and formerly unknown sequences of dissolution-precipitation reactions and pressure induced coalescence, segregation, aggregation, densification and growth processes. The weathering of the glass starts with its dissolution and subsequent precipitation of hydrous amorphous silica-bearing pockets rimmed by nano-size domains of ferrihydrite. An increase in molar volume during this process leads to an overall volume expansion, which promotes (a) growth of the hydrous silica through coalescence of individual pockets, (b) agglomeration of ferrihydrite domains to larger and denser aggregates in between layers or along the surfaces of plagioclase, hydrous amorphous silica and amorphous Al-(hydr)oxides, (c) formation of hematite within dense aggregates of ferrihydrite or as larger nanoparticles within an hydrous amorphous Si-Al-rich phase and (d) the break-up of plagioclase crystals and the replacement of these fragments by an hydrous amorphous Fe-Al-Si-bearing phase. At a later weathering stage, ferrihydrite nano-domains can also transform into magnetite/maghemite nanoparticles, which occur as layers around and on the surface of larger plagioclase crystals. This study also indicates the presence of past nano-environments in close proximity to each other, as for example layers of imogolite and ferrihydrite/hydrous amorphous silica occur only nanometers apart from each other on the opposite sides of unaltered glass. In accord with previous mineralogical studies of JSC MARS-1, the observed bulk and nano-mineralogical composition indicate that early alteration processes of basaltic glass under dry and cold conditions are mainly controlled by the formation of Fe-(hydr)oxides and minor imogolite and kaolinite. Recent mineralogical studies indicate that alteration processes at these conditions may have been the dominant weathering processes over long time periods on the Martian surface.

¹Wood, B.J.,¹Smythe, D.J.,¹Harrison, T.
American Mineralogist 104, 844-856 Link to Article [DOI: 10.2138/am-2019-6852CCBY]
¹Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, United Kingdom
Copyright: The Mineralogical Society of America

As part of a project to investigate the volatilities of so-called “moderately volatile elements” such as Zn, In, Tl, Ga, Ag, Sb, Pb, and Cl during planetary formation, we began by re-calculating the condensation temperatures of these elements from a solar gas at 10-4 bar. Our calculations highlighted three areas where currently available estimates of condensation temperature could be improved. One of these is the nature of mixing behavior of many important trace elements when dissolved in major condensates such as silicates, Fe-rich metals, and sulfides. Nonideal solution of the trace elements can alter (generally lower) condensation temperatures by up to 500 K. Second, recent measurements of the halogen contents of CI chondrites (Clay et al. 2017) indicate that the solar system abundance of chlorine is significantly overestimated, and this affects the stabilities of gaseous complexes of many elements of interest. Finally, we have attempted to improve on previous estimates of the free energies of chlorine-bearing solids since the temperature of chlorine condensation has an important control on the condensation temperatures of many trace elements. Our result for the 50% condensation temperature of chlorine, 472 K is nearly 500 K lower than the result of Lodders (2003), and this means that the HCl content of the solar gas at temperatures <900 K is higher than previously estimated. We based our calculations on the program PHEQ (Wood and Hashimoto 1993), which we modified to perform condensation calculations for the elements H, O, C, S, Na, Ca, Mg, Al, Si, Fe, F, Cl, P, N, Ni, and K by free energy minimization. Condensation calculations for minor elements were then performed using the output from PHEQ in conjunction with relevant thermodynamic data. We made explicit provision for nonidealities using information from phase diagrams, heat of solution measurements, partitioning data and by using the lattice strain model for FeS and ionic solids and the Miedema model for solutions in solid Fe. We computed the relative stabilities of gaseous chloride, sulfide, oxide, and hydroxide species of the trace elements of interest and used these, as appropriate in our condensation calculations. In general, our new 50% condensation temperatures are similar to or, because of the modifications noted above, lower than those of Lodders (2003).

¹María Isabel Varas-Reus,¹Stephan König,¹Aierken Yierpan,²Jean-Pierre Lorand,¹Ronny Schoenberg
Nature Geoscience (in Press) Link to Article [DOI
https://doi.org/10.1038/s41561-019-0414-7]
¹Isotope Geochemistry, Department of Geosciences, University of Tuebingen, Tuebingen, Germany
²Laboratoire de Planétologie et Géodynamique à Nantes, CNRS UMR 6112, Université de Nantes, Nantes, France

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¹P.G.Brown et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13368]
¹Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 Canada
²Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

The Hamburg (H4) meteorite fell on 17 January 2018 at 01:08 UT approximately 10 km north of Ann Arbor, Michigan. More than two dozen fragments totaling under 1 kg were recovered, primarily from frozen lake surfaces. The fireball initial velocity was 15.83 ± 0.05 km s⁻¹, based on four independent records showing the fireball above 50 km altitude. The radiant had a zenith angle of 66.14 ± 0.29° and an azimuth of 121.56 ± 1.2°. The resulting low inclination (<1°) Apollo‐type orbit has a large aphelion distance and Tisserand value relative to Jupiter (T_j) of ~3. Two major flares dominate the energy deposition profile, centered at 24.1 and 21.7 km altitude, respectively, under dynamic pressures of 5–7 MPa. The Geostationary Lightning Mapper on the Geostationary Operational Environmental Satellite‐16 also detected the two main flares and their relative timing and peak flux agree with the video‐derived brightness profile. Our preferred total energy for the Hamburg fireball is 2–7 T TNT (8.4–28 × 10⁹ J), which corresponds to a likely initial mass in the range of 60–225 kg or diameter between 0.3 and 0.5 m. Based on the model of Granvik et al. (2018), the meteorite originated in an escape route from the mid to outer asteroid belt. Hamburg is the 14th known H chondrite with an instrumentally derived preatmospheric orbit, half of which have small (<5°) inclinations making connection with (6) Hebe problematic. A definitive parent body consistent with all 14 known H chondrite orbits remains elusive.