Petrogenesis of main group pallasite meteorites based on relationships among texture, mineralogy, and geochemistry

1,5,6Seann J. MCKIBBIN,1,7Lidia PITTARELLO,1Christina MAKARONA,2,3
Christopher HAMANN,2,3Lutz HECHT,4,8Stepan M. CHERNONOZHKIN,1Steven GODERIS,1Philippe CLAEYS
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13392]
1Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium
2Museum fur Naturkunde, Leibniz-Institut fur Evolutions- und Biodiversitatsforschung, Invalidenstraße 43,
10115 Berlin, Germany
3Institut fur Geologische Wissenschaften, Freie Universitat Berlin, Malteserstraße 74-100, 12249 Berlin, Germany
4GeoRessources, Faculte des Sciences et Technologies, Universite de Lorraine, Rue Jacques Callot, BP 70239, 54506,
Vandoeuvre-les-Nancy CEDEX, France
5Present address: Institut f€ur Erd- und Umweltwissenschaften, Universitat Potsdam, Haus 27, Karl-Liebknecht-Straße 24-25,
Potsdam-Golm 14476, Germany
6Present address: Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Georg-August-Universitat Göttingen,
Goldschmidtstraße 1, Göttingen 37073, Germany
7Present address: Department of Lithospheric Research, Universit€at Wien, UZA 2, Althanstraße 14, Vienna A-1090,Austria
8Department of Chemistry, Universiteit Gent, Krijgslaan 281-S12, Ghent 9000, BelgiumPresent address: Department of Chemistry, Universiteit Gent, Krijgslaan 281-S12, Ghent 9000, Belgium
Published by arrangement with John Wiley & Sons

Main group pallasite meteorites are samples of a single early magmatic planetesimal, dominated by metal and olivine but containing accessory chromite, sulfide, phosphide, phosphates, and rare phosphoran olivine. They represent mixtures of core and mantle materials, but the environment of formation is poorly understood, with a quiescent core–mantle boundary, violent core–mantle mixture, or surface mixture all recently suggested. Here, we review main group pallasite data sets and petrologic characteristics, and present new observations on the low‐MnO pallasite Brahin that contains abundant fragmental olivine, but also rounded and angular olivine and potential evidence of sulfide–phosphide liquid immiscibility. A reassessment of the literature shows that low‐MnO and high‐FeO subgroups preferentially host rounded olivine and low‐temperature P2O5‐rich phases such as the Mg‐phosphate farringtonite and phosphoran olivine. These phases form after metal and silicate reservoirs back‐react during decreasing temperature after initial separation, resulting in oxidation of phosphorus and chromium. Farringtonite and phosphoran olivine have not been found in the common subgroup PMG, which are mechanical mixtures of olivine, chromite with moderate Al2O3 contents, primitive solid metal, and evolved liquid metal. Lower concentrations of Mn in olivine of the low‐MnO PMG subgroup, and high concentrations of Mn in low‐Al2O3 chromites, trace the development and escape of sulfide‐rich melt in pallasites and the partially chalcophile behavior for Mn in this environment. Pallasites with rounded olivine indicate that the core–mantle boundary of their planetesimal may not be a simple interface but rather a volume in which interactions between metal, silicate, and other components occur.

Presolar SiC Grains of Type AB with Isotopically Light Nitrogen: Contributions from Supernovae?

1Hoppe, P.,2,4,5,6Pignatari, M.,3Amari, S.
Springer Proceedings in Physics 219, 373-376 Link to Article [DOI: 10.1007/978-3-030-13876-9_68]
1Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, Mainz, 55128, Germany
2E. A. Milne Centre for Astrophysics, University of Hull, Hull, HU6 7RX, United Kingdom
3McDonnell Center for the Space Sciences and Physics Department, Washington University, St. Louis, MO 63130, United States
4NuGrid Collaboration, East Lansing, United States
5JINA-CEE, East Lansing, United States
6Konkoly Observatory, Konkoly Thege Miklos ut 15-17, Budapest, 1121, Hungary

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Hyperspectral imaging of drill core from the Steen River impact structure, Canada: Implications for hydrothermal activity and formation of suevite‐like breccias

1E. A. MacLagan,1,2E. L. Walton,1C. D. K. Herd,1B. Rivard
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13388]
1Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta T6G 2E3, Canada
2Department of Physical Sciences, MacEwan University, City Centre Campus, 10700 104 Ave, Edmonton, Alberta T5J 4S2, Canada
Published by Arrangement with John Wiley and Sons

Hyperspectral imaging can be used to rapidly identify and map the spatial
distributions of many minerals. Here, hyperspectral mapping in three wavelength regions(visible and near-infrared, shortwave infrared, and thermal infrared) was applied to drill cores (ST001, ST002, and ST003) penetrating a continuous sequence of crater-fill breccias from the Steen River impact structure in Alberta, Canada. The combined data sets reveal distinct mineralogical layering, with breccias derived predominantly from sedimentary rocks overlying those derived from granitic basement. This stratigraphy demonstrates that the
breccias were not appreciably disturbed following deposition, which is inconsistent with formation models of similar breccias (suevites) by explosive impact melt–fluid interaction. At Steen River, volatiles from sedimentary target rocks were an inherent part of forming these enigmatic breccias. Approximately three quarters of terrestrial impact structures contain sedimentary target rocks; therefore, the role of volatiles in producing so-called
suevitic breccias may be more widespread than previously realized. The hyperspectral maps, specifically within the SWIR wavelength region, also delineate minerals associated with postimpact hydrothermal activity, including ammoniated clay and feldspar minerals not detectable using traditional techniques. These nitrogen-bearing minerals may have originated from microbial processes, associated with oil- and gas-producing units in the
crater vicinity. Such minerals may have important implications for the production of habitable environments by impact-induced hydrothermal activity on Earth and Mars.

Attenuation of Ultraviolet Radiation in Rocks & Minerals: Implications for Mars Science

1B.L. Carrier,1W.J. Abbey,1L.W. Beegle,1R. Bhartia,1Y. Liu
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005758]
1Jet Propulsion Laboratory, California Institute of Technology
Published by arrangement with John Wiley & Sons

The effects of radiation on the survivability of key biosignatures are a driving factor in exploration strategies throughout the solar system. Ultraviolet (UV) radiation, especially shorter wavelength UVC radiation, is known to be damaging to organisms and to potential organic biosignatures; however the interaction of UV radiation with minerals and rocks is not well understood. Constraining the survivability of organics and generation of habitable zones requires assessment of physical parameters such as penetration depth of UV photons. This type of information helps to identify to what extent rocks and minerals can provide effective shielding against UV radiation and is especially important on Mars where the surface chemistry is more oxidizing and the radiation environment is more extreme than on Earth. Using pressed pellets of natural gypsum, kaolinite, Mars simulant basalt and welded tuff, we measured the spectral transmittance of each in the wavelength range of 220‐400 nm. Although transmittance drops off quickly with depth, detectable levels of UV can penetrate >500 μm in each material. Each substrate allowed higher transmittance of UVC radiation than of longer wavelength UVA/B radiation, possibly as a result of surface reflectance and internal scattering properties. This could result in increased subsurface photolysis of organic compounds and biosignatures. We have used the transmittance data collected herein to constrain the lifetimes of several organic molecules in the Martian subsurface. These results will also have implications for organic analyses to be conducted by Mars 2020, and could be used to better constrain the SHERLOC/Mars 2020 interrogation volume.

Determination of major to trace elements in metallic materials based on the solid mixing calibration method using multiple spot-laser ablation-ICP-MS

1Makino, Y.,2Kuroki, Y.,1Hirata, T.
Journal of Analytical Atomic Spectroscopy 34, 1794-1799 Link to Article [DOI: 10.1039/c9ja00181f]
1Geochemistry Research Center, School of Science, University of Tokyo Hongo, Tokyo, 113-0033, Japan
2Thermo Fisher Scientific K.K., Tokyo, 108-0023, Japan

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Critically testing olivine-hosted putative martian biosignatures in the Yamato 000593 meteorite—Geobiological implications

1McLoughlin, N.,1Grosch, E.G.,2,3Vullum, P.E., 4Guagliardo, P.,4,5Saunders, M.,4Wacey, D.
Geobiology (in Press) Link to Article [DOI: 10.1111/gbi.12361]
1Department of Geology, Rhodes University, Grahamstown, South Africa
2SINTEF Materials and Chemistry, Trondheim, Norway
3Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
4Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth, WA, Australia
5School of Molecular Sciences, The University of Western Australia, Perth, WA, Australia

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