¹Neyda M. Abreu
Geochmica et Cosmochimica Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.08.031]
¹Earth Science Program, The Pennsylvania State University – Du Bois Campus, Du Bois, PA 15801, USA
Copyright Elsevier

A number of different classification schemes have been proposed for the CR chondrites; this study aims at reconciling these different classification schemes. Mineralogy-based classification has proved particularly challenging for weakly to moderately altered CRs because incipient mineral replacement and elemental mobilization arising from aqueous alteration only affected the most susceptible primary phases, which are generally located in the matrix. Secondary matrix phases are extremely fine-grained (generally sub-micron) and heterogeneously mixed with primary nebular materials. Compositional and isotopic classification parameters are fraught with confounding factors, such as terrestrial weathering, impact processes, and variable abundance of clasts from different regions of the CR parent body or from altogether different planetary bodies. Here, detailed TEM observations from eighteen FIB sections retrieved from the matrices of nine Antarctic CR chondrites (EET 96259, GRA 95229, GRO 95577, GRO 03116, LAP 02342, LAP 04516, LAP 04720, MIL 07525, and MIL 090001) are presented, representing a range of petrologic types. Amorphous Fe-Mg silicates are found to be the dominant phase in all but the most altered CR chondrite matrices, which still retain significant amounts of these amorphous materials. Amorphous Fe-Mg silicates are mixed with phyllosilicates at the nanometer scale. The ratio of amorphous Fe-Mg silicates to phyllosilicates decreases as: (1) the size of phyllosilicates, (2) abundance of magnetite, and (3) replacement of Fe-Ni sulfides increase. Carbonates are only abundant in the most altered CR chondrite, GRO 95577. Nanophase Fe-Ni metal and tochilinite are present small abundances in most CR matrices. Based on the presence, abundance and size of phyllosilicates with respect to amorphous Fe-Mg silicates, the sub-micron features of CR chondrites have been linked to existing classification sequences, and possible reasons for inconsistencies among classification schemes are discussed.

¹Pizzarello, S.
Israel Journal of Chemistry (in Press)  Link to Article [DOI: 10.1002/ijch.201600039]
¹Arizona State University School of Molecular Sciences Tempe AZ 85018-1604 USA

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^1,2J. Kempl, ¹P.Z. Vroon, ¹B. van der Wagt, ³E. Zinngrebe, ⁴D.J. Frost, ¹W. van Westrenen
Netherlands Journal of Geosciences 95, 113-129  Link to Article [DOI: http://dx.doi.org/10.1017/njg.2015.34]
¹Faculty of Earth and Life Sciences, Vrije Universiteit University Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
²Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628CN Delft, the Netherlands
³Ceramics Research Center, Tata Steel IJmuiden, Building Code 3J-22, P.O. Box 1000, 1970 CA IJmuiden, the Netherlands
⁴Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany

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^1,2,3Valiev, R.R., ⁴Berezhnoy, A.A., ^1,5Minaev, B.F., ⁶Chernov, V.E., ¹Cherepanov, V.N.
Russian Physics Journal, Augus1 2016, 1-8 Link to Article [DOI: 10.1007/s11182-016-0803-y]
¹National Research Tomsk State University, Tomsk, Russian Federation
²National Research Tomsk Polytechnic University, Tomsk, Federation
³V. D. Kuznetsov Siberian Physical-Technical Institute at Tomsk State University, Tomsk, Russian Federation
⁴P. K. Sternberg Astronomical Institute at Moscow State University, Moscow, Russian Federation
⁵Bogdan Khmel’nitskii National University, Cherkassy, Ukraine
⁶Voronezh State University, Voronezh, Russian Federation

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¹Nicola Ferralis,²Emily D. Matys,³Andrew H. Knoll,²Christian Hallmann,²Roger E. Summons
Carbon 108, 440-449 Link to Article [http://dx.doi.org/10.1016/j.carbon.2016.07.039]
¹Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
²Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
³Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA

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¹Mark S. Bentley et al. (>10)*
Nature 537, 73-75 Link to Article [doi:10.1038/nature19091]
¹Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
*Find the extensive, full author and affiliation list on the publishers website

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¹Leitzke, F.P., ¹Fonseca, R.O.C., ¹Michely, L.T., ²Sprung, P., ²Münker, C., ^1,3Heuser, A., ¹Blanchard, H.
Chemical Geology 440, 219-238 Link to Article [10.1016/j.chemgeo.2016.07.011]
¹Steinmann-Institut für Geologie, Mineralogie un Paläontologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
²Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany
³GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Wischhofstraße 1-3, Kielz, Germany

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¹P. Boehnke, ¹T. Mark Harrison, ²M.T. Heizler, ¹P.H. Warren
Earth and Planetary Science Letters (in Press) Link to Article [http://dx.doi.org/10.1016/j.epsl.2016.07.014]
¹Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA 90095, United States
¹New Mexico Bureau of Geology and Mineral Resources, Socorro, NM 87801, United States
Copyright Elsevier

Results of whole-rock 40Ar/39Ar step-heating analyses of extra-terrestrial materials have been used to constrain the timing of impacts in the inner solar system, solidification of the lunar magma ocean, and development of planetary magnetic fields. Despite the importance of understanding these events, the samples we have in hand are non-ideal due to mixed provenance, isotopic disturbances from potentially multiple heating episodes, and laboratory artifacts such as nuclear recoil. Although models to quantitatively assess multi-domain, diffusive 40Ar⁎ loss have long been applied to terrestrial samples, their use on extra-terrestrial materials has been limited. Here we introduce a multi-activation energy, multi-diffusion domain model and apply it to 40Ar/39Ar temperature-cycling, step-heating data for meteoritic and lunar samples. We show that age spectra of extra-terrestrial materials, the Jilin chondrite (K-4) and Apollo 16 lunar breccia (67514,43)(67514,43), yielding seemingly non-ideal behavior commonly interpreted as either laboratory artifacts or localized shock heating of pyroxene, are meaningful and can be understood in context of the presence of multi-diffusion domains containing multiple activation energies. Internally consistent results from both the meteoritic and lunar samples reveal high-temperature/short duration thermal episodes we interpret as due to moderate shock heating.

¹Piero D Incecco, ¹Jörn Helbert, ¹Mario D Amore, ¹Sabrina Ferrari, ²James W. Head, ¹Alessandro Maturilli,³Harald Hiesinger
Planetary and Space Science (in Press) Link to Article [http://dx.doi.org/10.1016/j.pss.2016.08.004]
¹Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, D-12489 Berlin, Germany
²Department of Geological Sciences, Brown University, Providence, RI 02912, USA
³Westfälische Wilhelms-Universität Münster, Institut für Planetologie, Wilhelm-Klemm Str. 10, D-48149 Münster, Germany

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¹J.P. Pabari
Planetary and Space Science (in Press)   Link to Article [http://dx.doi.org/10.1016/j.pss.2016.08.008]
¹Physical Research Laboratory, Ahmedabad

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