Fe2+ partitioning between the M1 and M2 sites in silicate crystals in some stony and stony-iron meteorites studied using X-ray diffraction and Mössbauer spectroscopy

1Maksimova, A.A.,1Petrova, E.V.,1Chukin, A.V.,1Oshtrakh, M.I.
Journal of Molecular Structure 1216, 128391 Link to Article [DOI: 10.1016/j.molstruc.2020.128391]
1Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation

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Iron-nickel metallic components bearing silicate-melts and coesite from Ramgarh impact structure, west-central India: Possible identification of the impactor

1Ray, D.,2Misra, S.,3Upadhyay, D.,4Newsom, H.E.,4Peterson, E.J.,5Dube, A.,6Satyanaryanan, M.
Journal of Earth Science 129, 118 Link to Article [DOI: 10.1007/s12040-020-1371-7]
1Planetary Sciences Division, Physical Research Laboratory, Ahmedabad, 380 009, India
2Discipline of Geological Sciences, SAEES, University of KwaZulu-Natal, Durban, 4000, South Africa
3Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, 721 302, India
4Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States
58A-264, Salt Lake, Kolkata, 700 091, India
fCSIR-National Geophysical Research Institute, Hyderabad, 500 007, India

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The Cr-Zr-Ca armalcolite in lunar rocks is loveringite: Constraints from electron backscatter diffraction measurements

1,2Ai-Cheng Zhang,1Run-Lian Pang,3Naoya Sakamoto,3,4,5Hisayoshi Yurimoto
American Mineralogist 105, 1021–1029 Link to Article [http://www.minsocam.org/MSA/AmMin/TOC/2020/index.html?issue_number=07]
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, China
33Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan
4Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
5Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 252-5210, Japan
Copyright: The Mineralogical Society of America

“Cr-Zr-Ca armalcolite” is a mineral originally found in Apollo samples five decades ago. However, no structural information has been obtained for this mineral. In this study, we report a new occurrence of “Cr-Zr-Ca armalcolite” and its associated mineral assemblage in an Mg-suite lithic clast (Clast-20) from the brecciated lunar meteorite Northwest Africa 8182. In this lithic clast, plagioclase (An = 88–91), pyroxene (Mg#[Mg/(Mg+Fe)] = 0.87–0.91) and olivine (Mg# = 0.86–0.87) are the major rock-forming minerals. Armalcolite and “Cr-Zr-Ca armalcolite” are observed with other minor phases including ilmenite, chromite, rutile, fluorapatite, merrillite, monazite, FeNi metal, and Fe-sulfide. Based on 38 oxygen atoms, the chemical formula of “Cr-Zr-Ca armalcolite” is (Ca0.99Na0.01)S1.00(Ti14.22Fe2.06Cr2.01 Mg1.20Zr0.54Al0.49Ca0.21Y0.05Mn0.04Ce0.03Si0.03La0.01Nd0.01Dy0.01)S20.91O38. Electron backscatter diffraction (EBSD) results reveal that the “Cr-Zr-Ca armalcolite” has a loveringite R3 structure, differing from the armalcolite Bbmm structure. The estimated hexagonal cell parameters a and c of “Cr-Zr-Ca ar- malcolite” are 10.55 and 20.85 Å, respectively. These structural and compositional features indicate that “Cr-Zr-Ca armalcolite” is loveringite, not belonging to the armalcolite family. Comparison with “Cr-Zr-Ca armalcolite” and loveringite of other occurrences implies that loveringite might be an important carrier of rare earth elements in lunar Mg-suite rocks. The compositional features of pla- gioclase and mafic silicate minerals in Clast-20 differ from those in other Mg-suite lithic clasts from Apollo samples and lunar meteorites, indicating that Clast-20 represents a new example of diverse lunar Mg-suite lithic clasts.

First synthesis of a unique icosahedral phase from the Khatyrka meteorite by shock-recovery experiment

1Hu, J.,1Asimow, P.D.,1Ma, C.,2,3Bindi, L.
IUCrJ 7, 434-444 Link to Article [DOI: 10.1107/S2052252520002729]
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
2Dipartimento di Scienze della Terra, Università Degli Studi di Firenze, Firenze, I-50121, Italy
3Istituto di Geoscienze e Georisorse, Consiglio Nazionale Delle Ricerche, Firenze, I-50121, Italy

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Calibration of Raman wavenumber in large Raman images using a mercury-argon lamp

1Jakubek, R.S.,2Fries, M.D.
Journal of Raman Spectroscopy (in Press) Link to Article [DOI: 10.1002/jrs.5887]
1Astromaterials Research and Exploration Science (ARES) Division, Jacobs JETS Contract, NASA-JSC, Houston, TX, United States
2NASA Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston, TX, United States

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Shock tests and some considerations

1Aydan, Ö.,1Ito,1T.,1Tokashiki, N.,1Kodate, S.
Rock Mechanics for Natural Resources and Infrastructure Development- Proceedings of the 14th International Congress on Rock Mechanics and Rock Engineering, ISRM 2019, 1085-1092 Link to Article [ISBN: 978-036742284-4]
1Department. Of Civil Engineering, University of the Ryukyus, Okinawa, Nishihara, Japan

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Silica‐rich objects in the Acfer 182 CH chondrite: A new view

1Maria Eugenia Varela
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.1353]
1Instituto de Ciencias Astronómicas de la Tierra y del Espacio (ICATE)‐CONICET, Avenida España 1512 sur, J5402DSP San Juan, Argentina
Published by arrangement with John Wiley & Sons

Five silica‐rich objects (SRO) from Acfer 182 were studied. They have cryptocrystalline textures characterized by micro‐emulsion and amoeboid patterns that point toward the coexistence of pyroxene‐ and silica‐normative liquids that were quenched. Both objects have variable contents of refractory lithophile elements. Their positive Yb versus La correlation around primordial values suggests a cosmochemical process (e.g., a gas/liquid condensation) as responsible for SRO formation. The bulk trace element abundances of amoeboid‐ and emulsion‐type SRO as well as their fractionation do not support an origin through high temperature processes. Conversely, their formation might have taken place while cooling of the nebular gas in two different chondrule‐forming regions characterized by having different evolution paths. Cooling of these dust‐enriched regions might lead to the condensation of pyroxene‐rich liquids first, followed by formation of Mg‐rich and SiO2‐rich liquids, provided irradiation and annealing were active in these regions. Irradiation could be the process involved both in the formation of cristobalite (with annealing ~1200 K) and in triggering a spinoidal decomposition causing unmixing of the enstatite liquid into two coexisting phases, such as Mg‐rich and SiO2‐rich liquids, the precursors of the SRO in Acfer 182. Formation of emulsion‐ and amoeboid‐type objects may be the result of exposing those chondrule‐forming regions to different degrees of radiation.

Laboratory studies on the 3 μm spectral features of Mg-rich phyllosilicates with temperature variations in support of the interpretation of small asteroid surface spectra

Earth and Planetary Science Letters 546, 116424 Link to Article [https://doi.org/10.1016/j.epsl.2020.116424]
1Institute for Planetary Research, German Aerospace Center DLR, Rutherfordstr. 2, 12489 Berlin, Germany
Copyright Elsevier

Recent orbital data revealed the presence of hydrated minerals on the surfaces of asteroids, mainly through the identification and the study of the 3-μm spectral absorption band (Hamilton et al., 2019; Kitazato et al., 2019). The presence of an absorption feature around 3-μm on planetary bodies’ surfaces is indicative of the presence of OH-bearing minerals. This band has been widely detected on carbonaceous chondrites but its appearance and its shape are diverse indicating different composition and/or the occurrence of subsequent alteration events. In this work, we present the results of laboratory experiments performed at the Planetary Spectroscopy Laboratory (PSL) of the German Aerospace Center (DLR) to study the spectral behaviour of the 3-μm spectral features in the Mg-OH minerals with thermal variation. It has been suggested that thermal alteration processes, can darken the surfaces of carbonaceous chondrites, thus decreasing the appearance and visibility of the spectral features around 3 μm. Thermal alteration processes are consistent with the scenario currently proposed to explain the formation of 162173 Ryugu asteroid (Sugita et al., 2019). The Near Infrared Spectrometer (NIRS3) on the Hayabusa2 mission detected a weak and narrow absorption feature centred at 2.72 μm across the entire observed surface of the C-type asteroid (Kitazato et al., 2019). However, the collected spectra from the Ryugu surface show no other absorption features in the 3-μm region. To investigate this point further and analyze the variation of the spectral features around 3-μm with thermal alteration, we studied the Mg-rich phyllosilicates serpentine and saponite in two different situations: 1) thermal alteration at increasing temperature – the samples were heated at steps of 100 °C, starting from 100 °C up to 700 °C, for 4 hours each; 2) long time heating at constant temperature – samples were kept constantly at ∼250 °C for 1 month (1st step), then cooled down and measured in reflectance. This long heating process has been repeated at the same temperature of 250 °C for 2 months (2nd step). The results obtained show an important variation of phyllosilicates spectral bands with temperature and provide useful data for the interpretation of past and future mission small bodies collected surface spectra.

The sulfurization recorded in tridymite in the monomict eucrite Northwest Africa 11591

1,2Li‐Lin Huang,1,2Bing‐Kui Miao,1,2Guo‐Zhu Chen,1,2Hui‐Min Shao,3Zi‐Yuan Ouyang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13495]
1Institution of Meteorites and Planetary Materials Research, Guilin University of Technology, Guilin, 541004 China

2Key Laboratory of Planetary Geological Evolution, Guilin University of Technology, Guilin, 541004 China
3Key Laboratory of Lunar and Deep Space Exporation, CAS, Beijing, 100101 China
Published by arrangement with John Wiley & Sons

Some of the tridymite in the monomict Northwest Africa (NWA) 11591 eucrite are found to have sulfide‐rich replacement textures (SRTs) to varying degrees. The SRTs of tridymite in NWA 11591 are characterized by the distribution of loose porous regions with aggregates of quartz and minor troilite grains along the rims and fractures of the tridymite, and we propose a new mechanism for the origin of this texture. According to the volume and density conversion relationship, the quartz in the SRT of tridymite with a hackle fracture pattern was transformed from tridymite. We suggest that the primary tridymite grains are affected by the S‐rich vapors along the rims and fractures, leading to the transformation of tridymite into quartz. In addition, the S‐rich vapors reacted with Fe2+, which was transported from the relict tridymite and/or the adjacent Fe‐rich minerals, and/or the S‐rich vapors react with the exotic metallic Fe to form troilite grains. The sulfurization in NWA 11591 most likely occurred during the prolonged subsolidus thermal metamorphism in the shallow crust of Vesta and might be an open, relatively high temperature (>800 °C) process. Sulfur would be an important component of the metasomatic fluid on Vesta.