¹Katherine H. Joy, ²Ian A. Crawford, ¹Natalie M. Curran, ^3,4Michael Zolensky, ⁵Amy F. Fagan, ³David A. Kring
Earth, Moon, and Planets (in Press) Link to Article [DOI: 10.1007/s11038-016-9495-0]
¹School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
²Department of Earth and Planetary Sciences, Birkbeck College, University of London, London, UK
³Center for Lunar Science and Exploration, The Lunar and Planetary Institute – USRA, Houston, USA
⁴ARES, NASA Johnson Space Center, Houston, USA
⁵Geosciences and Natural Resources Department, 331 Stillwell Building, Western Carolina University, Cullowhee, USA

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¹Yuhei Umeda, ¹Atsushi Takase, ¹Nao Fukunaga ^1,2Toshimori Sekine, ³Takamichi Kobayashi, ⁴Yoshihiro Furukawa, ⁴Takeshi Kakegawa
Physics and Chemistry of Minerals (in Press) Link to Article [doi:10.1007/s00269-016-0849-y]
¹Department of Earth and Planetary Systems Science Hiroshima University Higashi-Hiroshima Japan
²Center for High Pressure Science and Technology Advanced Research Pudong People’s Republic of China
³National Institute for Materials Science Tsukuba Japan
⁴Department of Earth and Planetary Materials Science Tohoku University Sendai Japan

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^1,2,3Jangmi Han, ¹Adrian J. Brearley
Geochmica et Cosmochimica Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.10.014]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA
²Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA
³NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, USA
Copyright Elsevier

We have studied four melilite-rich calcium-aluminum-rich inclusions (CAIs) from the Allan Hills A77307 CO3.0 chondrite using transmission electron microscopy with the focused ion beam sample preparation technique. This type of CAI represents one of the dominant types of refractory inclusions in CO3 chondrites. Individual melilite-rich CAIs 04 to 07 record complex formational histories involving high-temperature gas-solid condensation that occurred under both equilibrium and disequilibrium conditions. CAI 04 contains two texturally- and compositionally-distinct occurrences of perovskite: fine-grained perovskite within a melilite-rich core and aggregates of perovskite grains that surround the core. The textural and compositional differences suggest that the perovskite aggregates condensed after core formation under different conditions. CAI 05 consists of a compact melilite-rich core surrounded by a porous mantle, and likely formed by at least two different condensation events under different conditions. In CAI 06, complex intergrowth layers surrounding a melilite-rich core indicate reaction of spinel and melilite with a nebular gas to form Al-Ti-rich diopside following core formation. CAI 07 is dominated by melilite with a narrow compositional range and equilibrated textures, suggesting its formation by condensation over a limited temperature range. Collectively, we infer that the melilite-rich inclusions formed by a generalized sequence of high-temperature gas-solid condensation that involved: (1) formation of CAI cores by aggregation of primary equilibrium condensate grains (i.e., perovskite, spinel, and melilite), (2) back-reactions of the primary core minerals with a nebular gas under disequilibrium conditions, forming diopside that evolves in composition from Al-Ti-rich at the interface with the inclusion core to Al-Ti-poor on the exterior of the inclusions. The change in formation conditions may have been achieved by transport and injection of the core materials into a region of a partially-condensed gas that still contained refractory elements in the gas phase.

¹Patrick N. Peplowski
Planetary and Space Science (in Press) Link to Article [http://dx.doi.org/10.1016/j.pss.2016.10.006]
¹The Johns Hopkins University Applied Physics Laboratory, Laurel MD 20723

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^1,2Timothy Gregory,¹Katherine Helen Joy,³Stanislav Strekopytov,¹Natalie Mary Curran
Meteoritics & Planetary Science (in Press) Link to Article [10.1111/maps.12782]
¹School of Earth and Environmental Science, University of Manchester, Manchester, UK
²School of Earth Sciences, University of Bristol, Bristol, UK
³Imaging and Analysis Centre, The Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The howardite-eucrite-diogenite (HED) clan of meteorites, which most likely originate from the asteroid Vesta, provide an opportunity to combine in-depth sample analysis with the comprehensive remote-sensing data set from NASA’s recent Dawn mission. Miller Range (MIL) 11100, an Antarctic howardite, contains diverse rock and mineral fragments from common HED lithologies (diogenites, cumulate eucrites, and basaltic eucrites). It also contains a rare pyroxferroite-bearing lithology—not recognized in HED until recently—and rare Mg-rich (Fo86-91) olivine crystals that possibly represent material excavated from the Vestan mantle. Clast components underwent different histories of thermal and impact metamorphism before being incorporated into this sample, reflecting the diversity in geological histories experienced by different parts of Vesta. The bulk chemical composition and petrography of MIL 11100 suggest that it is akin to the fragmental howardite meteorites. The strong lithological heterogeneity across this sample suggests that at least some parts of the Vestan regolith show heterogeneity on the mm-scale. We combine the outcomes of this study with data from NASA’s Dawn mission and hypothesize on possible source regions for this meteorite on the surface of Vesta.

¹N. G. Rudraswami,¹K. Reshma,¹M. Shyam Prasad
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12783]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, India
Published by arrangement with John Wiley & Sons

Micrometeorites provide a large range of samples sourced from a wide variety of planetary materials, thereby providing a scope for expanding the known inventory of solar system materials. Here we report the micrometeorite AAS62-34-P117 having the assemblage of corundum, hibonite, unknown Al-rich phases, FeNi metal blebs, sulfide, and phosphate embedded in Al-rich silicate composition, and Pt-group element nuggets dispersed throughout the micrometeorite. Here, we report the presence of corundum in micrometeorites as a major refractory phase with sizes greater than ~10 μm. The Al-rich phases have Al2O3 ~50–70%, such high Al phases are not known from meteoritic components either in chondrules or refractory inclusions. In addition, the Ca content is extremely poor to relate it directly to known refractory inclusions, but is very high in Al. The presence of corundum in Al-rich phases indicates the micrometeorite to be early condensate from solar nebula that later got incorporated into Si-rich materials leading to a transformation that produced the unusual Al-rich and Ca-poor phases different from the average solar composition. The observed texture and mineralogy of the micrometeorite appears to have evolved in a nebular setting that has compositional reservoirs different from those of any known components of meteorites.

¹Anatolii V. Fisenko,²Sasha B. Verchovsky,^3,4Andrei A. Shiryaev,¹Luba F. Semjonova
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12743]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Moscow, Russia
²Department of Physical Sciences, The Open University, Milton Keynes, UK
³Institute of Physical Chemistry and Electrochemistry RAS, Moscow, Russia
⁴Institute of Geology of Ore Deposit, Petrography, Geochemistry and Mineralogy RAS s, Moscow, Russia
Published by arrangement with John Wiley & Sons

A nanodiamond-rich fraction (NDF) separated from the Orgueil meteorite was subjected to a high-intensity ultrasonic treatment in a weakly acidic aqueous solution. After sedimentation by centrifugation, two fractions of grains (suspension, designated as OD7C and sediment, designated as OD7D) with different properties have been obtained. The following effects of the sonication were revealed from comparison of the contents and isotope compositions of C, N, and Xe released during stepped pyrolysis and combustion of the fractions OD7C and OD7D, the initial NDF and two grain-size fractions (OD10 and OD15) produced without sonication (a) surface layer of the sonicated diamond grains is modified to different extent in comparison with nontreated ones, (b) in some grains concentrations of the bulk N and Xe a reduced significantly, and (c) nondiamond nitrogen containing phases (e.g., Si3N4) have been destroyed. It is suggested that combined effects of the sonication and centrifugation observed for the fractions OD7C and OD7D are due to differences in surface chemistry of the nanodiamond grains, which statistically influences behavior of nanoparticles during the sonication resulting in their preferential modification in the different reaction zones of the cavitating fluid.

¹Nicholas Castle, ¹Christopher D. K. Herd
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12739]
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
Published by arrangement with John Wiley & Sons

Tissint is an olivine-phyric shergottite from an incompatible element depleted Martian mantle source. Oxythermobarometry applied to Tissint mineral phases demonstrates that the Tissint magma underwent an increase in oxygen fugacity, from ~3.5 log units below the quarz-fayalite-magnetite (QFM) buffer during the early stages of crystallization, to QFM−1.4 during the latter stages. This is the first time that such an oxidation event has been observed in a depleted shergottite. The reason for the oxidation event is unclear; however, calculations using the MELTS thermodynamic model suggest that auto-oxidation is insufficient to cause more than ~1 log unit of oxidation, and therefore an external oxidation mechanism—such as oxidation by degassing—is required. If volatiles are responsible for the oxidation, then it indicates that volatiles are not exclusively tied to the enriched Martian mantle reservoir. A series of experiments using the Tissint parental magma were carried out under fixed (isothermal) or variable (cooling rate) temperature control, and at either reducing (QFM−3.2) or oxidizing (QFM−1) redox conditions. The observed liquid line of descent supports a potential genetic relationship between basaltic shergottites and olivine-phyric shergottites. A peritectic relation where olivine is resorbed to form pyroxene is favored by increased oxygen fugacity; if oxidation during crystallization is more common than presently believed, it may explain why olivine is typically anhedral in olivine-phyric shergottites. Results from a cooling-rate experiment in which the oxygen fugacity was changed during the latter stages of crystallization resulted in olivine with a Cr compositional profile consistent with oxidized isothermal experiments, despite forming primarily under reducing conditions. A similar profile is observed in Tissint olivines, consistent with its redox history. Our results provide insights into the potential influence of oxidation events on the compositional zoning of minor or trace elements in olivine in olivine-phyric basalts.

¹Dwijesh Ray,¹S. Ghosh,¹S.V.S. Murty
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12742]
¹Planetary Sciences Division, Physical Research Laboratory, Ahmedabad, India
Published by arrangement with John Wiley & Sons

Microtextural study of a single troilite-metal nodule (TMN) from the Katol L6-7 chondrite, a recent fall (May, 2012) in India suggests that the TMN is primarily an aggregate of submicron-scale intergrowth of troilite and kamacite (mean Ni: 6.18 wt%) juxtaposed with intensely fractured silicates, mainly olivine (Fa: 25 mole%), low-Ca pyroxene (Fs: 21.2 mole%), and a large volume of maskelynite. Evidence of shock textures in the TMN indicates a high degree of shock metamorphism that involves plagioclase-maskelynite and olivine-wadsleyite/ringwoodite transformations and formation of quenched metal-sulfide melt textures due to localized shear-induced frictional melting. It is inferred that the TMN formation is an independent, localized event by a high energy impact and its subsequent incorporation in the ejected chondritic fragment of the parent body. Katol chondrite has been calibrated with a peak shock pressure of S5 (~45 GPa) after Stöffler et al. (1991), whereas peak shock pressure within the TMN exceeds the shock facies S6 (>45 GPa) following Bennett and McSween (1996) and Stöffler et al. (1991). Overall, the shock-thermal history of the Katol TMN is dissimilar as compared to the host chondrite.

^1,2A. Calzada-Diaz,³K. H. Joy,^1,2I. A. Crawford,⁴S. Strekopytov
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12737]
¹Department of Earth and Planetary Sciences, Birkbeck College, London WC1E 7HX, UK
²Centre for Planetary Sciences UCL/Birkbeck, London WC1E 7HX, UK
³School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
⁴Imaging and Analysis Centre, Natural History Museum, London SW7 5BD, UK
Published by arrangement with John Wiley & Sons

Meteorites ejected from the surface of the Moon as a result of impact events are an important source of lunar material in addition to Apollo and Luna samples. Here, we report bulk element composition, mineral chemistry, age, and petrography of Miller Range (MIL) 090036 and 090070 lunar meteorites. MIL 090036 and 090070 are both anorthositic regolith breccias consisting of mineral fragments and lithic clasts in a glassy matrix. They are not paired and represent sampling of two distinct regions of the lunar crust that have protoliths similar to ferroan anorthosites. 40Ar-39Ar chronology performed on two subsplits of MIL 090070,33 (a pale clast impact melt and a dark glassy melt component) shows that the sample underwent two main degassing events, one at ~3.88 Ga and another at ~3.65 Ga. The cosmic ray exposure data obtained from MIL 090070 are consistent with a short (~8–9 Ma) exposure close to the lunar surface. Bulk-rock FeO, TiO2, and Th concentrations in both samples were compared with 2-degree Lunar Prospector Gamma Ray Spectrometer (LP-GRS) data sets to determine areas of the lunar surface where the regolith matches the abundances observed on the sample. We find that MIL 090036 bulk rock is compositionally most similar to regolith surrounding the Procellarum KREEP Terrane, whereas MIL 090070 best matches regolith in the feldspathic highlands terrane on the lunar farside. Our results suggest that some areas of the lunar farside crust are composed of ferroan anorthosite, and that the samples shed light on the evolution and impact bombardment history of the ancient lunar highlands.