¹Hadrien A.R. Devillepoix et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13142]
¹School of Earth and Planetary Sciences, Curtin UniversityBentley, WA, Australia
Published by arrangement with John Wiley & Sons

We describe the fall of the Dingle Dell (L/LL 5) meteorite near Morawa in Western Australia on October 31, 2016. The fireball was observed by six observatories of the Desert Fireball Network (DFN), a continental‐scale facility optimized to recover meteorites and calculate their pre‐entry orbits. The 30 cm meteoroid entered at 15.44 km s−1, followed a moderately steep trajectory of 51° to the horizon from 81 km down to 19 km altitude, where the luminous flight ended at a speed of 3.2 km s−1. Deceleration data indicated one large fragment had made it to the ground. The four person search team recovered a 1.15 kg meteorite within 130 m of the predicted fall line, after 8 h of searching, 6 days after the fall. Dingle Dell is the fourth meteorite recovered by the DFN in Australia, but the first before any rain had contaminated the sample. By numerical integration over 1 Ma, we show that Dingle Dell was most likely ejected from the Main Belt by the 3:1 mean motion resonance with Jupiter, with only a marginal chance that it came from the ν6 resonance. This makes the connection of Dingle Dell to the Flora family (currently thought to be the origin of LL chondrites) unlikely.

¹Arya Udry, ²James M.D.Day
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.07.006]
¹Department of Geoscience, University of Nevada Las Vegas, Las Vegas NV 89154, USA
²Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0244, USA
Copyright Elsevier

Nakhlite and chassignite martian meteorites have similar crystallization (1340 ± 40 Ma) and ejection (∼11 Ma) ages, and 87Rb-87Sr and 143Sm-144Nd compositions. Using a near-comprehensive suite of these rocks, we place further constraints on nakhlite and chassignite petrogenesis, utilizing bulk rock and mineral major- and trace-element compositions, and quantitative textural data for 17 samples, including three recent finds (Northwest Africa [NWA] 10153, NWA 10645, and NWA 11013). Bulk rock and mineral compositions indicate that nakhlites and chassignites originated from <5% partial melting of a highly depleted source, in the presence of residual garnet. Significant fractionation of olivine and pyroxene from parental magmas led to formation of cumulate dunites (chassignites), and augite-rich cumulates with relatively low abundances of interstitial material (nakhlites). We show that two nakhlite groups exist with high and low absolute trace-element abundances, which are consistent with groupings from previous studies based on mesostasis content and volatile element contents. The discrepancy between the parental melt and cumulate bulk rock compositions indicates that a missing fractionated melt composition complementary to nakhlites and chassignites should exist on Mars. Quantitative textural analyses of both nakhlites and chassignites are consistent with emplacement as distinct lava flows and/or magmatic bodies close to the martian surface, rather than from a single sill or lava flow sequence. Although originating from the same parental melt to nakhlites, chassignites likely represent cumulates that were either erupted as xenoliths, or occurred as crystal settling pods within dikes or sills and thus represent a different batch of flow/magma from the nakhlites. Determination of an ancient 207Pb-206Pb age (3.95 ± 0.16 Ga) for an apatite grain in NWA 998 is consistent with hydrothermal alteration of nakhlites by ancient crustal-derived fluids immediately following their emplacement. We interpret the apatite age, which is highly distinct from the crystallization age of nakhlites, to indicate addition of Cl-rich fluids driven by hydrothermal circulation of martian crustal brines during emplacement of the nakhlites and chassignites. Although the spatial location of nakhlites and chassignites at the martian surface remains unconstrained, our results indicate similar emplacement features to those observed in terrestrial volcano-magmatic systems.

¹Tomomi Omura, ¹Akiko M. Nakamura
The Astrophysical Journal 860, 123 Link to Article [https://doi.org/10.3847/1538-4357/aabe81]
¹Department of Planetology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo, 657-8501, Japan

The porosity structure of a granular body is an important characteristic that affects evolutionary changes in the body. We conducted compression experiments using fluffy granular samples with various particle sizes, shapes, and compositions. We approximated the pressure-filling factor relationship of each sample with a power law (a modified polytropic relationship). We also fit our previous data and literature data for fluffy granular samples using a power-law equation. The fitting with a power-law form was as good as that achieved with the equations used for powders in previous studies. The polytropic indices obtained in the current study ranged from ~0.01 to ~0.3 and tended to decrease with increasing particle size for samples of similar porosities. We calculated the radial porosity structure and bulk porosity of granular bodies with various radii using the Lane–Emden equation. The results provide the initial, most porous structures of accreted primordial bodies, or re-accumulated rubble-pile bodies consisting of particles that have compression properties similar to those of the assumed granular materials. A range of porosity structures is allowed for a body of given size and macroporosity, depending on the compression properties of the constituent granular material.

¹Scott A.Wipperfurth, ^1,2Meng Guo, ³Ondřej Šrámek, ^1,4William F.McDonough
Earth and Planetary Science Letters (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2018.06.029]
¹Department of Geology, University of Maryland, College Park, MD 20742, USA
²Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
³Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
⁴Research Center for Neutrino Science and Department of Earth Sciences, Tohoku University, Sendai 980-8578, Japan
Copyright Elsevier

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹W.Rapin et al. (>10)
Journal of Geophysical Research Planets (in Press) Link to Article [https://doi.org/10.1029/2017JE005483]
¹Division of Geological and Planetary Sciences, California Institute of TechnologyPasadena, CA, USA
Published by arrangement with John Wiley & Sons

Silica enrichments resulting in up to ~90 wt% SiO2 have been observed by the Curiosity rover’s instruments in Gale crater, Mars within the Murray and Stimson formations. Samples acquired by the rover drill revealed a significant abundance of an X‐ray amorphous silica phase. Laser induced breakdown spectroscopy (LIBS) highlights an overall correlation of the hydrogen signal with silica content for these Si‐enriched targets. The increased hydration of the high‐silica rocks compared to the surrounding bedrock is also confirmed by active neutron spectroscopy. Laboratory LIBS experiments have been performed to calibrate the hydrogen signal and show that the correlation observed on Mars is consistent with a silica phase containing on average 6.3 ± 1.4 wt% water. X‐ray diffraction and LIBS measurements indicate that opal‐A, amorphous hydrated silica, is the most likely phase containing this water in the rocks. Pyrolysis experiments were also performed on drilled samples by the Sample Analysis at Mars (SAM) instrument to measure volatile content, but the data suggests that most of the water was released during handling prior to pyrolysis. The inferred low‐temperature release of water helps constrain the nature of the opal. Given the geological context and the spatial association with other phases such as calcium sulfates, the opal was likely formed from multiple diagenetic fluid events and possibly represents the latest significant water‐rock interaction in these sedimentary rocks.

^1,2Christopher Hamann, ^1,2Saskia Bläsing, ^1,2Lutz Hecht, ⁴³Sebastian Schäffer, ⁴Alex Deutsch, ³Jens Osterholz, ³Bernd Lexow
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13133]
¹Museum für Naturkunde, Leibnitz‐Institut für Evolutions‐ und Biodiversitätsforschung, Berlin, Germany
²Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany
³Fraunhofer‐Institut für Kurzzeitdynamik, Ernst‐Mach‐Institut, Freiburg, Germany
⁴Institut für Planetologie, Westfälische Wilhelms‐Universität Münster, Münster, Germany
Published by arrangement with John Wiley & Sons

We simulated entrainment of carbonates (calcite, dolomite) in silicate impact melts by 1‐bar laser melting of silicate–carbonate composite targets, using sandstone, basalt, calcite marble, limestone, dolomite marble, and iron meteorite as starting materials. We demonstrate that carbonate assimilation by silicate melts of variable composition is extremely fast (seconds to minutes), resulting in contamination of silicate melts with carbonate‐derived CaO and MgO and release of CO₂ at the silicate melt–carbonate interface. We identify several processes, i.e., (1) decomposition of carbonates releases CO₂ and produces residual oxides (CaO, MgO); (2) incorporation of residual oxides from proximally dissociating carbonates into silicate melts; (3) rapid back‐reactions between residual CaO and CO₂ produce idiomorphic calcite crystallites and porous carbonate quench products; (4) high‐temperature reactions between Ca‐contaminated silicate melts and carbonates yield typical skarn minerals and residual oxide melts; (5) mixing and mingling between Ca‐ or Ca,Mg‐contaminated and Ca‐ or Ca,Mg‐normal silicate melts; (6) precipitation of Ca‐ or Ca,Mg‐rich silicates from contaminated silicate melts upon quenching. Our experiments reproduce many textural and compositional features of typical impact melts originating from silicate–carbonate targets. They reinforce hypotheses that thermal decomposition of carbonates, rapid back‐reactions between decomposition products, and incorporation of residual oxides into silicate impact melts are prevailing processes during impact melting of mixed silicate–carbonate targets. However, by comparing our results with previous studies and thermodynamic considerations on the phase diagrams of calcite and quartz, we envisage that carbonate impact melts are readily produced during adiabatic decompression from high shock pressure, but subsequently decompose due to heat influx from coexisting silicate impact melts or hot breccia components. Under certain circumstances, postshock conditions may favor production and conservation of carbonate impact melts. We conclude that the response of mixed carbonate–silicate targets to impact might involve melting anddecomposition of carbonates, the dominant response being governed by a complex variety of factors.

^1,2Beda A. Hofmann et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13132]
¹Natural History Museum Bern, Bern, Switzerland
²Institute for Geological Sciences, University of Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

Meteorite searches in Saudi Arabia between 2008 and 2014 yielded 46 meteorites from the Yabrin area (23°N 49°E), 35 meteorites from the Rub’ al‐Khali sand desert (19°–20°N, 48°–51°E), and 1 meteorite from Al Haddar. No meteorites were found near Hafar al Batin (29°N 45°E). The 82 new meteorites represent ~57 falls comprising 43 ordinary chondrites, 4 carbonaceous chondrites, 2 enstatite chondrites, 3 ureilites, 3 eucrites, 1 acapulcoite, and 1 lunar meteorite. The median of 31 14C terrestrial ages is 6.2 ka, significantly younger than the Oman population (19.5 ka, n = 128). A further assessment of terrestrial 14C contamination is advised by a 11–15 ka 14C terrestrial age of heavily weathered meteorite Khawr al Fazra 014, geology indicating a terrestrial age >100 ka. Find densities of 0.4–2.8 km−2 for Yabrin and the western Rub’ al‐Khali are similar to ~0.5 km−2 observed in Oman. Higher find densities of ~135 km−2 (29 km−2 for masses >10 g) exist on small Pleistocene outcrops in blowouts in the south‐central Rub’ al‐Khali: 21 unpaired meteorites (four >10 g) were found in 11 blowouts with a combined area of 0.14 km2. The Rub’ al‐Khali meteorites show a relatively high degree of weathering (median W 3.6; 2.5 for Yabrin), low median mass (4.3/138 g), and a high H/L ratio (2.3/1.1). The high density of small meteorites is explained by prolonged sand protection and recent deflation. The high meteorite density and relatively high proportion of rare meteorite types render the Rub’ al‐Khali blowouts an interesting target for future exploration.

¹Stig M. Bergström, ²Birger Schmitz,³Huaibao P. Liu, ¹Fredrik Terfelt, ³Robert M. McKay
Lethaia (in Press) Link to Article [https://doi.org/10.1111/let.12269]
¹School of Earth Sciences, The Ohio State University, Columbus, OH, USA
²Division of Nuclear Physics, Department of Physics, Lund University, Lund, Sweden
³Iowa Geological Survey, IIHR‐Hydroscience & Engineering, University of Iowa, Iowa City, IA, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

^1,2Luca Bindi, ^3,4Xiande Xie
european Journal of Mineralogy 30, 165-169 Link to Article [https://doi.org/10.1127/ejm/2017/0029-2684]
¹Dipartimento di Science de la Terra, Università degli Studi di Firenze, Via G. La Pira, 4, 50121Firenze, Italy
²CNR – Istituto di Geoscienze e Georisorse, Sezione di Firenze, Via G. La Pira 4, 50121Firenze, Italy
³Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou510640, China
⁴Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou510640, China

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

^1,2Tatyana G. Shumilova, ¹Sergey I. Isaenko, ¹Vasily V. Ulyashev, ³Valery A. Kazakov, ¹Boris A. Makeev
European Journal of Mineralogy 30, 61-76 Link to Article [https://doi.org/10.1127/ejm/2018/0030-2715]
¹Institute of Geology, Komi Scientific Center of Ural Division of Russian Academy of Sciences, Pervomayskaya st. 54, Syktyvkar167982,
Russia
²Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, 1680 East-West Road, Honolulu, HI96822,
USA
³SSC FSUE Keldysh Research Centre, Onezhskaya, 8, Moscow125438,
Russia

We currently do not have a copyright agreement with this publisher and cannot display the abstract here