¹Yong Xiong,^1,2Ai‐Cheng Zhang,³Noriyuki Kawasaki,⁴Chi Ma, ⁵Naoya Sakamoto,⁵Jia‐Ni Chen,⁶Li‐Xin Gu,^3,5Hisayoshi Yurimoto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13575]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³Department of Natural History Sciences, Hokkaido University, Sapporo, 060‐0810 Japan
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125 USA
⁵Isotope Imaging Laboratory, Creative Research Institution Sousei, Hokkaido University, Sapporo, 001‐0021 Japan
⁶Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
Published by arrangement with John Wiley & Sons

Calcium‐aluminum‐rich inclusions (CAIs) are the first solid materials formed in the solar nebula. Among them, ultrarefractory inclusions are very rare. In this study, we report on the mineralogical features and oxygen isotopic compositions of minerals in a new ultrarefractory inclusion CAI 007 from the CV3 chondrite Northwest Africa (NWA) 3118. The CAI 007 inclusion is porous and has a layered (core–mantle–rim) texture. The core is dominant in area and mainly consists of Y‐rich perovskite and Zr‐rich davisite, with minor refractory metal nuggets, Zr,Sc‐rich oxide minerals (calzirtite and tazheranite), and Fe‐rich spinel. The calzirtite and tazheranite are closely intergrown, probably derived from a precursor phase due to thermal metamorphism on the parent body. The refractory metal nuggets either exhibit thin exsolution lamellae of Fe,Ni‐dominant alloy in Os,Ir‐dominant alloy or are composed of Os,Ir,Ru,Fe‐alloy and Fe,Ni,Ir‐alloy with troilite, scheelite, gypsum, and molybdenite. The later four phases are apparently secondary minerals. The Zr,Sc,Y‐rich core is surrounded by a discontinuous layer of closely intergrown hibonite and spinel. The CAIs are rimmed by Fe‐rich spinel and Al‐rich diopside. Perovskite has high concentrations of the most refractory rare earth elements (REEs) but is relatively depleted in the moderately refractory and volatile REEs, consistent with the ultrarefractory REE pattern. Based on this unusual Zr,Sc,Y‐rich mineral assemblage, the layered distribution in CAI 007, and the REE concentrations in perovskite, we suggest that CAI 007 is an ultrarefractory inclusion of condensation origin. In CAI 007, hibonite, spinel, and probably Al‐rich diopside are ¹⁶O‐rich (Δ¹⁷O ~–22‰) whereas perovskite and davisite are ¹⁶O‐poor (Δ¹⁷O ~–3‰). Such oxygen isotope heterogeneity suggests that the UR inclusion formed in the various degrees of ¹⁶O‐rich nebular setting or was originally ¹⁶O‐rich and then experienced oxygen isotope exchange with ¹⁶O‐poor fluid on the CV3 chondrite parent body.

¹Aleksandra N. Stojic et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114162]
¹Institut für Planetologie, Westfälische Wilhelms Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
Copyright Elsevier

We conducted classic dynamic high – pressure experiments on porous San Carlos (SC) olivine powder to examine if and how different shock stages modify corresponding reflectance mid – infrared (MIR) spectra. Microscopic investigation of the thin sections produced of our shocked samples indicates local peak pressures of >60 GPa along with all lower grade shock stages. Spectral analyses of optically identified shock areas were documented and compared in terms of Christiansen Feature (CF) and the position of olivine – diagnostic Reststrahlenbands (RBs). We found that one RB (fundamental vibrations of the orthosilicate – ion) of olivine occurring at 980 cm−1 (corresponding to ≈ 10.2 μm) shows the least energetic shift in the investigated MIR spectra and could therefore serve as a proxy for the presence of olivine in remote sensing application. Furthermore, a peak located at ≈ 1060 cm−1 (≈ 9.4 μm) shows a significant intensity change probably related to the degree of shock exposure or grain orientation effects, as we observe a decline in intensity of this band from our averaged reference olivine spectra of our IRIS database (diffuse reflectance measurement) down to spectra of grains showing mosaicism and recrystallized areas. We also report the presence of a weak band in some of the olivine spectra located at ≈ 1100 cm−1 (9.1 μm) that has an influence on the position of the CF when spectral data of olivine are averaged.

¹Naoki Hirakawa,¹Yoko Kebukawa,¹Kensei Kobayashi,²Hideyuki Nakano
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114167]
¹Graduate School of Engineering Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
²Faculty of Culture and Sport Policy, Toin University of Yokohama, 1614 Kurogane-cho, Aoba-ku, Yokohama 225-8503, Japan
Copyright Elsevier

Molecular structures and chemical compositions of organic matter in primitive meteorites reflect the conditions of the parent bodies, as well as the preaccretional history. During the parent body processing, co-existing minerals could have effects on structural changes of organics, in addition to temperature and redox state. Here, we performed heating experiments of a primordial organic matter analog with and without minerals to understand the effects of minerals on organic matter in conditions simulating metamorphism in thermally metamorphosed type 3 chondrites. The primordial analog materials were heated up to 400 °C, and the experimental products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS). Montmorillonite and olivine, particularly montmorillonite, enhanced decomposition of oxygen containing species due to decarboxylation and/or cracking, while olivine enhanced esterification at lower temperature. Our results further imply that the variations of insoluble organic matter in CV, CO, and type 3 ordinary chondrites could be partially due to different mineral compositions. We also tested the effects of pressure on the degradation of the organic matter at 400 °C up to 268 atm, however no significant pressure effects were observed by FTIR and GC/MS.

^1,2J.Pape,¹Å.V.Rosén,¹K.Mezger,³M.Guillong
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.10.019]
¹Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland
Copyright Elsevier

Chondrules from unequilibrated ordinary chondrites are among the oldest Solar system materials and preserve mineralogical, chemical and isotopic signatures that link them to their primary formation mechanisms and environments in the early Solar System. Some chondrules record features indicating modifications by high- to low-temperature processes throughout their residence time in the protoplanetary disk. Chondrules that were partially modified after their primary formation record chemical, isotopic and textural information on their initial formation conditions and subsequent reprocessing that are essential to reconstruct their formation environments and interpret the ages recorded by individual chondrules correctly.

The detailed textural and major, minor and trace element analyses of two type-I chondrules from the low petrologic type ordinary chondrites MET 00526 and MET 00452 (L/LL3.05) reveal complex chemical and textural systematics bearing testimony of their multi-stage high temperature evolution, including reheating and partial remelting, in the evolving protoplanetary disk prior to accretion into their parent bodies. During primary crystallization of chondrule MET00526_Ch43, mineral growth, including incipient formation of feldspar in the outer parts of the chondrule, led to the fractionation of melt, eventually resulting in a chemical gradient in the mesostasis. During a later punctuated reheating that ultimately led to partial remelting of the outer parts of the chondrule, mesostasis and low-Ca pyroxene remelted partially. This partial remelting enhanced the chemical differences within the mesostasis and led to the formation of two chemically distinct mesostases in the inner and the outer zone of the chondrule with almost complementary abundances of Rb, Na, K, Ba, Sr and Eu. The calculated bulk mesostasis composition reveals chondritic relative abundances of these elements in the bulk chondrule with a slight depletion of the most volatile elements. Chemical and textural observations further indicate that this disequilibrium remelting occurred under more reducing conditions than the primary melting event preserved in the chondrule centre, allowing for the crystallization of a second generation of low-Ca pyroxene in the outer parts of the chondrule. Very similar processes are also recorded in chondrule MET00452_Ch22 with the degree of remelting being more extensive.

A previously determined young 26Al-26Mg age of ∼3 Ma after CAIs determined for chondrule MET00452_Ch22 dates the time of the chondrule remelting rather than its primary formation. This is evidence for a late thermal event in the protoplanetary disk and generally indicates that multiple, distinct thermal pulses occurred in the chondrule forming region of the protoplanetary disk throughout the time of chondrule formation. The nonconcentric secondary outer zone around a spherical inner zone may indicate a directed heat source as the cause of partial remelting and reprocessing of primary chondrules.

¹Zuriñe Yoldi,¹Antoine Pommerol,^1,2Olivier Poch,¹Nicolas Thomas
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114169]
¹Physikalisches Institut, Universität Bern and NCCR PlanetS, Sidlerstrasse 5, 3012 Bern, Switzerland
²Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
Copyright Elsevier

The reflectance of water ice and dust mixtures depends, amongst other parameters, on how the components are mixed (e.g. intimate mixture, areal mixture or coating) (Clark, 1999). Therefore, when inverting the reflectance spectra measured from planetary surfaces to derive the amount of water ice present at the surface, it is critical to distinguish between different mixing modes of ice and dust. However, the distinction between mixing modes from reflectance spectra remains ambiguous. Here we show how to identify some water ice/soil mixing modes from the study of defined spectral criteria and colour analysis of laboratory mixtures. We have recreated ice and dust mixtures and found that the appearance of frost on a surface increases its reflectance and flattens its spectral slopes, whereas the increasing presence of water ice in intimate mixtures mainly impacts the absorption bands. In particular, we provide laboratory data and a spectral anal

^1,2Kohei Fukuda,¹Hajime Hiyagon,³Wataru Fujiya,^4,7Takanori Kagoshima,^1,6Keita Itano,¹Tsuyoshi Iizuka,²Noriko T.Kita,^4,5Yuji Sano
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.10.011]
¹Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
²WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706, USA
³Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
⁴Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
⁵Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, People’s Republic of China
⁶Present address: College of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
⁷Present address: Department of Environmental Biology and Chemistry, School of Science, University of Toyama, Toyama 930-8555, Japan
Copyright Elsevier

We have performed in situ analyses of Li-Be-B and Al-Mg isotope systematics, and abundances of rare earth elements (REEs) in two Ca-Al-rich inclusions (CAIs) from the Ornans-like carbonaceous chondrite Yamato-81020 (CO3.05). The present CO CAIs are depleted in ultra-refractory heavy REEs (group II REE pattern), suggesting condensation of these CAIs or their precursors from the solar nebula. Initial 26Al/27Al ratios, (26Al/27Al)0, of these CO CAIs are found to be (4.8 ± 0.5) × 10–5 and (4.9 ± 0.3) × 10–5 (2σ), indicating their contemporaneous formation with a majority of CAIs from CV chondrites. Melilite grains in the present CO CAIs show clear excesses in 10B, ranging from ∼370 to ∼4300‰ relative to the chondritic B isotopic composition, which are correlated well with 9Be/11B ratios. The correlation indicates in situ decay of 10Be in the present CO CAIs and yields initial 10Be/9Be ratios, (10Be/9Be)0, for the individual CAIs of (2.9 ± 0.6) × 10–3 and (2.2 ± 1.0) × 10–3 (2σ), which are significantly greater than the average (10Be/9Be)0 = ∼0.7 × 10–3 recorded in CAIs from Vigarano-like carbonaceous (CV) chondrites. The apparent variation in (10Be/9Be)0 between the CO and CV CAIs, despite having indistinguishable (26Al/27Al)0 of ∼5 × 10–5, provides evidence for heterogeneous distribution of 10Be in the CAI forming-regions at the very beginning of the Solar System. The elevated (10Be/9Be)0 and group II REE patterns in the CO CAIs may reflect that compared with the CV CAIs having unfractionated REEs the present CO CAIs have formed closer to the Sun where 10Be was produced more efficiently through solar cosmic ray irradiation caused by solar flares. Alternatively, if the present CO CAIs and CV CAIs formed in the same region, and 26Al was distributed homogeneously at the CAI-forming region, our results indicate that solar cosmic ray fluxes at the forming region have fluctuated by a factor of six within a short duration (∼0.2 million years) inferred from the Al-Mg chronology.

¹Badyukov, D.D.
Solar System Research 54, 263-274 Link to Article [DOI: 10.1134/S0038094620040024]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991, Russian Federation

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¹Kimura, M.,¹Imae, N.,²Komatsu, M.,³Barrat, J.A.,⁴Greenwood, R.C.,¹Yamaguchi, A.,⁵Noguchi, T.
Polar Science (in Press)  Link to Article [DOI: 10.1016/j.polar.2020.100565]
¹National Institute of Polar Research, Tokyo, 190-8518, Japan
²SOKENDAI, Kanagawa, 240-0193, Japan
³Université de Bretagne Occidentale, Institut Universitaire Europé en de La Mer, CNRS UMR 6538, Place Nicolas Copernic, Plouzané 29280, France
⁴Planetary and Space Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom
⁵Kyushu University, Fukuoka, 819-0395, Japan

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¹Krishnamurthy, P.
Journal of the Geological Society of India 96, 111-147 Link to Article [DOI: 10.1007/s12594-020-1521-1]
¹Department of Atomic Energy, Begumpet, Formerly Atomic Minerals Directorate for Exploration and Research (AMD), Hyderabad, 500 016, India

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¹Blukis, R.,²Pfau, B.,³Günther, C.M.,²Hessing, P.,^2,4Eisebitt, S., Einsle,⁵J.,⁶Harrison, R.J.
Geochemistry, Geophysics, Geosystems 21, e2020GC009044 Link to Article [DOI: 10.1029/2020GC009044]
¹GFZ German Centre for Geosciences, Potsdam, Germany
²Max-Born-Institut, Berlin, Germany
³Center for Electron Microscopy (ZELMI), Technische Universität Berlin, Berlin, Germany
⁴Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin, Germany
⁵School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom
⁶Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom

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