^1,2,3Gunther Kletetschka
Earth and Planetary Science Letters 487, 1-8 Link to Article [https://doi.org/10.1016/j.epsl.2018.01.020]
¹Institute of Geology, Academy of Sciences of the Czech Republic, Czech Republic
²Faculty of Science, Charles University, Czech Republic
³Department of Geology and Geophysics, University of Alaska Fairbanks, USA
Copyright Elsevier

The origin of magnetization in Allende may have significant implications for our understanding of core formation/differentiation/dynamo processes in chondrite parent bodies. The magnetic Allende data may contain information that could constrain the magnetic history of Allende. The measurements on Allende chondrules reveal an existence of magnetization component that was likely acquired during the meteorite transit to terrestrial conditions. Both the pyrrhotite carrying magnetic remanence intensity and direction of the chondrules change erratically when subjecting the Allende meteorite’s chondrules to temperatures near 77 K and back to room temperature. Chondrules with more intense original magnetization are denser and contain larger inverse thermoremanent magnetization (ITRM). Temperature dependent monitoring of ITRM revealed that magnetization was acquired at temperature near 270 K. Such temperature is consistent with the condition when, in addition to temperature increase, the atmospheric uniaxial pressure applied during the meteorite entry on the porous material was responsible for meteorite break up in the atmosphere. During this process, collapse of the pore space in the matrix and some chondrules would generate crystalline anisotropy energy accumulation within pyrrhotite grains in form of parasitic magnetic transition.

¹Maurizio Gemelli,¹Tommaso Di Rocco,¹Luigi Folco,¹Massimo D’Orazio
Geostandards and Geoanalytical Research 41, 613-632 Link to Article [DOI: 10.1111/ggr.12179]
¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy

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¹Tomoaki Kubo, ²Mari Kono, ^1,2Masahiro Imamur, ¹Takumi Kato, ¹Seiichiro Uehara, ³Tadashi Kondo, ⁴Yuji Higo, ⁴Yoshinori Tange, ⁵Takumi Kikegawa
Physics of the Earth and Planetary Interiors 272, 50-57 Link to Article [https://doi.org/10.1016/j.pepi.2017.09.006]
¹Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan
²Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, Fukuoka 819-0395, Japan
³Department of Earth Space Science, Osaka University, Osaka 560-0043, Japan
⁴Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan
⁵Photon Factory, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan

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^1,2Albert Jambon
Journal of Archaeological Science 88, 47-53 Link to Article [https://doi.org/10.1016/j.jas.2017.09.008]
¹Université Côte D’Azur, UPMC, CNRS, OCA, IRD, Géoazur, Sophia Antipolis, France
²Sorbonne Universités, UPMC Univ Paris 06, MNHN and IMPMC, France

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¹Patrick H. Donohue, ¹Clive R. Neal
American Mineralogist 103, 284-297 Link to Article [DOI: https://doi.org/10.2138/am-2018-6173]
¹Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, U.S.A.
Copyright: The Mineralogical Society of America

Basalt fragment 71597 is the sole high-titanium mare basalt showing evidence for olivine accumulation during formation. The petrogenesis of this unique sample was investigated using quantitative textural analysis and major- and trace-element mineral geochemistry. Crystal size distribution analysis identified two size populations of olivine, which we separate into cumulate and matrix olivine. The spatial distribution of olivine also supports clustering of olivine crystals, likely during accumulation. Observed mineral chemistry was consistent with an origin through olivine accumulation, although where this occurred cannot be discerned (e.g., in ponded melts at the base of or in the lunar crust, or within a thick high-Ti basalt flow). Attempts to place 71597 within a geochemical group were inconclusive both using subtraction of cumulate olivine from bulk composition, and by modal recombination of major phases. However, equilibrium liquid compositions of augite and plagioclase are determined to be consistent with an origin by fractionation from the Type B2 chemical suite of Apollo 17 high-Ti basalts. This method of classification has potential for placing other Type U (“Unclassified”) basalts into chemical suites.

^1,2Fan Wang, ³Brenda B. Bowen, ⁴Ji-Hye Seo, ^2,4Greg Michalski
American Mineralogist 103, 197-206 Link to Article [DOI: https://doi.org/10.2138/am-2018-6141]
¹School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen, Guangdong 518055, China
²Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, U.S.A.
³Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, U.S.A.
⁴Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, U.S.A.
Copyright: The Mineralogical Society of America

Large amounts of nitrate salts occur in very specific environments and somewhat rare hyper-arid conditions, which may provide clues to fundamentally different nitrogen cycling and life survival mechanisms. Remote detection of ancient and modern nitrates on Earth and on other planetary bodies where they may occur requires a detailed understanding of their visible to near infrared (VNIR) spectral signatures. This study explores the VNIR spectral characteristics of several synthetic nitrate salts, sulfate minerals, and nitrate-bearing field samples from the Atacama Desert, Chile, to identify diagnostic spectral features of nitrate and possible interferences from other coexisting minerals. Results indicated that most of the nitrate salts have characteristic absorptions around 1.81, 1.94, 2.06, 2.21, and 2.42 μm. A significant positive correlation exists between the continuum-removed band depths of the 2.42 μm absorption and nitrate contents for the Atacama regolith samples, especially for samples with >10 wt% nitrate. The five absorption features of nitrate in the field spectra collected from multiple nitrate-rich regions in the Atacama Desert were then evaluated to determine the variabilities in these features in natural settings, while the band depths of 2.42 μm absorption were further calculated on the continuum-removed field spectra to estimate the nitrate abundances at the study sites. This work will supplement spectral libraries where nitrate spectra are lacking and have implications for future comparisons to planetary spectra to search for potentially life-related nitrate on Mars.

¹James W. Dottin III, ¹James Farquhar, ²Jabrane Labidi
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.01.013]
¹Department of Geology, University of Maryland, College Park, MD 20742, USA
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
Copyright Elsevier

This study reports the quadruple sulfur isotope composition of troilite nodules from Main Group Pallasites. Values range from -0.23‰ to 0.34‰ (average = 0.03±0.17‰ S.D.) in δ34S and 0.008‰ to 0.025‰ (average = 0.018± 0.006‰ S.D.) in Δ33S and -0.38 to -0.01 (average = -0.17±0.11‰ S.D.) in Δ36S. The variance of these analyses is comparable to estimates of analytical uncertainty (±0.3‰, ± 0.008‰, and ±0.3‰, for δ34S, Δ33S, and Δ36S, respectively) and the average of these values is taken as a constraint on the composition of sulfur in the MG Pallasite parent body. The different Δ33S value compared to CDT and IAB iron meteorites at a similar δ34S value is interpreted as a mass-independent signature. This signature is similar in magnitude and direction to previously published values observed in IIIAB iron meteorites, further supporting a genetic relationship between the two groups of meteorites.

¹Nancy N. Elewa, ¹J. M. Cadogan
Hyperfine Interactions 238, 4 Link to Article [https://doi.org/10.1007/s10751-016-1350-1]
¹School of Physical, Environmental and Mathematical Sciences The University of New South Wales at the Australian Defence Force Academy Canberra Australia

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¹J. Galazka-Friedman, ²M. Woźniak, ¹P. Duda, ¹P. Rzepecka, ¹M. Jakubowska, ³Ł. Karwowski
Hyperfine Interactions 238, 67 Link to Article [https://doi.org/10.1007/s10751-017-1439-1]
¹Faculty of Physics Warsaw University of Technology Warsaw Poland
²Faculty of Biology University of Warsaw Warsaw Poland
³Faculty of Earth Sciences University of Silesia Sosnowiec Poland

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¹Nao Nakanishi,¹Tetsuya Yokoyama,¹Satoki Okabayashi,²Tomohiro Usui,^1,3Hikaru Iwamori
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13050]
¹Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, Japan
²Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo, Japan
³Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
Published by arrangement with John Wiley & Sons

We report Os isotope compositions of metal grains in two CBa chondrites (Bencubbin and Gujba) determined using a micromilling sampling coupled with thermal ionization mass spectrometry, together with the abundances of major and trace siderophile elements obtained by electron probe microanalysis and femtosecond laser ablation inductively coupled plasma–mass spectrometry. The CBa metal grains presented 187Os/188Os ratios akin to carbonaceous chondrites with limited variations (0.1257–0.1270). Most of the CBa metal grains were scattered along a 187Re-187Os reference isochron of IIIAB iron meteorites, indicating that the CBa metals experienced limited Re-Os fractionation at the time of their formation. The Re/Os ratios of sampling spots for the CBa metals, recast from the observed 187Os/188Os ratios, had a positive correlation with their Os/Ir ratios. In addition, the metal grains showed a positive correlation in a Pd/Fe versus Ni/Fe diagram. These correlations suggest that the CBa metal grains have formed via equilibrium condensation or evaporation from a gaseous reservoir at ~10−4 bar with enhanced metal abundances. Compared to the Bencubbin metals, the Gujba metals are characterized by having systematically lower Pd/Fe and Ni/Fe ratios that span subchondritic values. Such a difference was most likely induced by the compositionally heterogeneous impact plume from which the metals were condensed.