¹Chi Ma,²Oliver Tschauner,¹John R. Beckett,¹George R. Rossman,³Clemens Prescher,³Vitali B. Prakapenka,⁴Hans A. Bechtel,⁴Alastair MacDowell
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13000]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²High Pressure Science and Engineering Center and Department of Geoscience, University of Nevada, Las Vegas, Nevada, USA
³Center of Advanced Radiation Sources, GSECARS, The University of Chicago, Chicago, Illinois, USA
⁴Advanced Light Source, ESG, Lawrence Berkeley National Laboratory, Berkeley, California, USA
Published by arrangement with John Wiley & Sons

In this paper, we discuss the occurrence of liebermannite (IMA 2013-128), KAlSi3O8, a new, shock-generated, high-pressure tetragonal hollandite-type structure silicate mineral, in the Zagami basaltic shergottite meteorite. Liebermannite crystallizes in space group I4/m with Z = 2, cell dimensions of a = 9.15 ± 0.14 (1σ) Å, c = 2.74 ± 0.13 Å, and a cell volume of 229 ± 19 Å3 (for the type material), as revealed by synchrotron diffraction. In Zagami, liebermannite likely formed via solid-state transformation of primary igneous K-feldspar during an impact event that achieved pressures of ~20 GPa or more. The mineral name is in honor of Robert C. Liebermann, a high-pressure mineral physicist at Stony Brook University, New York, USA.

¹Carl Palk,¹Rasmus Andreasen,¹Mark Rehkämper,¹Alison Stunt,¹Katharina Kreissig,¹Barry Coles,²Maria Schönbächler,³Caroline Smith
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12989]
¹Department of Earth Science & Engineering, Imperial College London, London, UK
²Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
³Department of Mineralogy, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

New Tl, Pb, and Cd concentration and Tl, Pb isotope data are presented for enstatite as well as L- and LL-type ordinary chondrites, with additional Cd stable isotope results for the former. All three chondrite suites have Tl and Cd contents that vary by more than 1–2 orders of magnitude but Pb concentrations are more uniform, as a result of terrestrial Pb contamination. Model calculations based on Pb isotope compositions indicate that for more than half of the samples, more than 50% of the measured Pb contents are due to addition of modern terrestrial Pb. In part, this is responsible for the relatively young and imprecise Pb-Pb ages determined for EH, L, and LL chondrites, which are hence only of limited chronological utility. In contrast, four particularly pristine EL chondrites define a precise Pb-Pb cooling age of 4559 ± 6 Ma. The enstatite chondrites (ECs) have highly variable ε114/110Cd of between about +3 and +70 due to stable isotope fractionation from thermal and shock metamorphism. Furthermore, nearly all enstatite meteorites display ε205Tl values from −3.3 to +0.8, while a single anomalous sample is highly fractionated in both Tl and Cd isotopes. The majority of the ECs thereby define a correlation of ε205Tl with ε114/110Cd, which suggests that at least some of the Tl isotope variability reflects stable isotope fractionation rather than radiogenic ingrowth of 205Tl from 205Pb decay. Considering L chondrites, most ε205Tl values range between −4 and +1, while two outliers with ε205Tl ≤ −10 are indicative of stable isotope fractionation. Considering only those L chondrites which are least likely to feature Pb contamination or stable Tl isotope effects, the results are in accord with the former presence of live 205Pb on the parent body, with an initial 205Pb/204Pb = (1.5 ± 1.4) × 10−4, which suggests late equilibration of the Pb-Tl system 26–113 Ma after carbonaceous chondrites (CCs). The LL chondrites display highly variable ε205Tl values from −12.5 to +14.9, also indicative of stable isotope effects. However, the data for three pristine LL3/LL4 chondrites display an excellent correlation between ε205Tl and 204Pb/203Tl. This defines an initial 205Pb/204Pb of (1.4 ± 0.3) × 10−4, equivalent to a 205Pb-205Tl cooling age of 55 + 12/−24 Ma (31–67 Ma) after CCs.

¹E. A. Pilles,^1,2G. R. Osinski,¹R. A. F. Grieve,³D. A. Smith,³J. M. Bailey
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12986]
¹Department of Earth Sciences/Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada
²Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada
³Wallbridge Mining Company Limited, Sudbury, Ontario, Canada
Published by arrangement with John Wiley & Sons

Offset dikes are found concentrically around—and extending radially outward from—the Sudbury Igneous Complex (SIC), which represents an ~3 km thick differentiated impact melt sheet. The dikes are typically composed of an inclusion-rich, so-called quartz diorite (IQD) in the center of the dike, and an inclusion-poor quartz diorite (QD) along the margins of the dike. New exposures of the intersection between the concentric Hess and radial Foy offset dikes provide an excellent opportunity to understand the relationship between the radial and concentric offset dikes and their internal phases. The goal was to constrain the timing of the dike emplacements relative to the impact and formation of the SIC. Results herein suggest that (1) the timing between the emplacement of the QD and IQD melts was geologically short, (2) the Hess and Foy dikes coexisted as melts at the same time and the intersection between them represents a mixture of the two, (3) the Foy dike has a slightly more evolved chemical composition than the Hess dike, and (4) the IQD melt from the Foy dike underwent some degree of chemical fractionation after its initial emplacement.

^1,2Yuto Kidokoro, ²Koichiro Umemoto, ²Kei Hirose, ³Yasuo Ohishi
American Mineralogist 102, 2230-2234 Link to Article [DOI
https://doi.org/10.2138/am-2017-6033]
¹Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
²Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
³Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
Copyright: The Mineralogical Society of America

We have investigated the phase transition in SiC between the zinc-blende and rock-salt structures at high pressure and temperature in a laser-heated diamond-anvil cell. Results demonstrate that the transition occurs at 74 GPa and 2100 K with a 21% density increase, reflecting the coordination number rising from four to six. In addition, our ab initio calculations show that the boundary has a negative Clapeyron slope of −4.0 MPa/K at 2000 K. The experimentally determined phase boundary is located between those predicted by GGA and B3LYP functional. This transition may take place inside carbon-rich extrasolar planets, forming a boundary with a large density jump. Since SiC is rigid and highly thermally conductive, thermal convection in an SiC-dominant layer is not likely to occur. Nevertheless, the convection may be possible if planet interiors include both silicon carbide and silicate, and in this case the phase transition could affect the style of thermal convection.

^1,2Carsten Münker, ²Raúl O. C. Fonseca, ³Toni Schulz
Nature Geoscience 10, 822-826 Link to Article [doi:10.1038/ngeo3048]
¹Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Strasse 49b, 50674 Köln, Germany
²Steinmann Institut, Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, German
³Department für Lithosphärenforschung, Universität Wien, Althanstrasse 14, 1090 Wien, Austria

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

¹M. I. F. Barth,¹D. Harries,¹F. Langenhorst,²P. Hoppe
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12992]
¹Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, Jena, Germany
²Max-Planck-Institut für Chemie, Mainz, Germany
Published by arrangement with John Wiley & Sons

The ungrouped carbonaceous chondrite Acfer 094 is among the least altered samples of the early solar system. We have studied concentric sulfide–oxide aggregates from this meteorite by transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS). The main minerals present are magnetite, pentlandite, and pyrrhotite/troilite. The outer parts of the aggregates include μm-sized olivine and pyroxenes with variable Mg/Fe ratios. One aggregate contains taenite (56.7 wt% Ni) within its central part that is surrounded by pentlandite and magnetite. We conclude that both phases have formed by oxidation and sulfidization of metal and, based on the metal and sulfide Fe/Ni ratio, a (sulfide)-formation temperature of 400–550 °C can be constrained. This temperature is higher than any temperature that could be expected to have occurred on the Acfer 094 parent body, and also textural evidence indicates that the aggregates formed before parent-body accretion. We therefore conclude that the formation of the sulfide–oxide aggregates occurred most likely in the solar nebular at highly variable H2O and H2S fugacities. Oxygen-isotopic compositions of magnetite within these assemblages show that they are indistinguishable from the meteorite’s matrix (δ17OSMOW ≈ 4 ± 8‰, δ18OSMOW ≈ 10 ± 6‰, and ∆17OSMOW ≈ −1 ± 5‰). An enrichment of 17,18O relative to chondrules of Acfer 094 suggests a link between the formation of the sulfide–oxide aggregates and the preaccretionary processing of matrix grains in a volatile-enriched nebular environment.

^1,2Naoya Imae,³Yoshihiro Nakamuta
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12996]
¹Antarctic Meteorite Research Center, National Institute of Polar Research, Tachikawa, Tokyo, Japan
²Department of Polar Science, School of Multidisciplinary Sciences, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo, Japan
³Kyushu University Museum, Kyushu University, Fukuoka, Japan
Published by arrangement with John Wiley & Sons

Using the in-plane rotation of polished thin section, the X-ray diffraction patterns exhibiting a high degree of randomness similar to powder pattern were obtained for 10 CO3 chondrites, which distinguished 130 reflections of olivine in the chondrules from that in the matrix, and showed systematic differences among subtypes based on the full width at half maximum intensity of two olivine 130 peaks. A lower petrologic subtype is characterized by sharp and strong peaks for forsteritic olivines in type I chondrules and by a weak and broad peak for ferroan matrices, and the higher petrologic subtypes are characterized by sharp and strong peaks for recrystallized matrices and a weakened or absent peak of magnesian olivines. The systematic change in the split peak of olivine 130 was linked with the mean diffusion length of Mg-Fe in olivine phenocrysts in type I chondrules. Fe-Ni diffusion in metals was considered to estimate the peak temperature of CO3.0, near the surface on the parent body. The peak metamorphic temperatures were estimated to be ~600–910 K using the onion-shell model when the cooling time was 106–108 yr on the parent body. A weak peak for ferroan olivine of CO3.0 suggests the amorphous silicate in matrices. The modal abundance of the amorphous Fe-silicate for subtype 3.0 (15% for Allan Hills [ALH] 77307 and 9% for Yamato [Y]-81020) was also evaluated from the deviation in trend of the relative peak ratios of the Fe-rich (≥Fa25) and Mg-rich (<Fa25) olivines for subtypes. The existence of martensites was suggested for ALH 77307. Amorphous silicate in matrices is a more resistant primordial component that produced the CO3 chondrites than martensite.

¹Chizu Kato, ^1,2Frédéric Moynier
Earth and Planetary Science Letters 479, 330-339 Link to Article [https://doi.org/10.1016/j.epsl.2017.09.028]
¹Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR 7154, Paris, France
²Institut Universitaire de France, 75005, Paris, France
Copyright Elsevier

The abundance of moderately volatile elements, such as Zn and Ga, show variable depletion relative to CI between the Earth and primitive meteorite (chondrites) parent bodies. Furthermore, the first solar system solids, the calcium–aluminum-rich inclusions (CAIs), are surprisingly rich in volatile element considering that they formed under high temperatures. Here, we report the Ga elemental and isotopic composition of a wide variety of chondrites along with five individual CAIs to understand the origin of the volatile elements and to further characterize the enrichment of the volatile elements in high temperature condensates. The δ71Ga (permil deviation of the 71Ga/69Ga ratio from the Ga IPGP standard) of carbonaceous chondrites decreases in the order of CI>CM>CO>CV and is inversely correlated with the Al/Ga ratio. This implies that the Ga budget of the carbonaceous chondrites parent bodies were inherited from a two component mixing of a volatile rich reservoir enriched in heavy isotope of Ga and a volatile poor reservoir enriched in light isotope of Ga. Calcium–aluminum-rich inclusions are enriched in Ga and Zn compared to the bulk meteorite and are both highly isotopically fractionated with δ71Ga down to −3.56‰ and δ66Zn down to −0.74‰. The large enrichment in the light isotopes of Ga and Zn in the CAIs implies that the moderately volatile elements were introduced in the CAIs during condensation in the solar nebula as opposed to secondary processing in the meteorite parent body and supports a change in gas composition in which CAIs were formed.

¹Jan Leitner,¹Peter Hoppe,²Jutta Zipfel
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12994]
¹Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
²Sektion Meteoritenforschung, Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt, Germany
Published by arrangement with John Wiley & Sons

We report on the investigation of presolar grain inventories of hydrated lithic clasts in three metal-rich carbonaceous chondrites from the CR clan, Acfer 182 (CH3), Isheyevo (CH3/CBb3), and Lewis Cliff (LEW) 85332 (C3-un), as well as the carbon- and nitrogen-isotopic compositions of the fine-grained clast material. Eleven presolar silicate grains as well as nine presolar silicon carbide (SiC) grains were identified in the clasts. Presolar silicate abundances range from 4 to 22 parts per million (ppm), significantly lower than in pristine meteorites and interplanetary dust particles (IDP), and comparable to recent findings for CM2s and CR2 interchondrule matrix. SiC concentrations lie between 9 and 23 ppm, and are comparable to the values for CI, CM, and CR chondrites. The results of our investigation suggest similar alteration pathways for the clast material, the interchondrule matrix of the CR2 chondrites, and the fine-grained fraction of CM2 chondrites. Fine-grained matter of all three meteorites contains moderate to high 15N-enrichments (~50‰ ≤ δ15N ≤ ~1600‰) compared to the terrestrial value, indicating the presence of primitive organic material. We observed no correlation between 15N-enrichments and presolar dust concentrations in the clasts. This is in contrast to the findings from a suite of primitive IDPs, which display in several cases enhanced bulk 15N/14N ratios and high presolar grain abundances of several hundred or even thousand ppm. The bulk 15N/14N ratios of the clasts are comparable to the range for primitive IDPs, suggesting a nitrogen carrier less susceptible to destruction by aqueous alteration than silicate stardust.

^1,2,3Surya S. Rout,^1,2,4Philipp R. Heck,⁵Dieter Isheim,^1,2,4Thomas Stephan,⁶Nestor J. Zaluzec,⁷Dean J. Miller,^1,2,4,8Andrew M. Davis,⁴David N. Seidman
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12988]
¹Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, Illinois, USA
²Chicago Center for Cosmochemistry, Chicago, Illinois, USA
³Physikalisches Institut, Space Research and Planetary Sciences, Universität Bern, Bern, Switzerland
⁴Department of the Geophysical Sciences, The University of Chicago, Chicago, Illinois, USA
⁵Department of Material Science & Engineering, Northwestern University Center for Atom-Probe Tomography, Northwestern University, Evanston, Illinois, USA
⁶Photon Science Division, Argonne National Laboratory, Argonne, Illinois, USA
⁷Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, USA
⁸Enrico Fermi Institute, The University of Chicago, Chicago, Illinois, USA
Published by arrangement with John Wiley & Sons

We report the first combined atom-probe tomography (APT) and transmission electron microscopy (TEM) study of a kamacite–tetrataenite (K–T) interface region within an iron meteorite, Bristol (IVA). Ten APT nanotips were prepared from the K–T interface with focused ion beam scanning electron microscopy (FIB-SEM) and then studied using TEM followed by APT. Near the K-T interface, we found 3.8 ± 0.5 wt% Ni in kamacite and 53.4 ± 0.5 wt% Ni in tetrataenite. High-Ni precipitate regions of the cloudy zone (CZ) have 50.4 ± 0.8 wt% Ni. A region near the CZ and martensite interface has <10 nm sized Ni-rich precipitates with 38.4 ± 0.7 wt% Ni present within a low-Ni matrix having 25.5 ± 0.6 wt% Ni. We found that Cu is predominantly concentrated in tetrataenite, whereas Co, P, and Cr are concentrated in kamacite. Phosphorus is preferentially concentrated along the K-T interface. This study is the first precise measurement of the phase composition at high spatial resolution and in 3-D of the K-T interface region in a IVA iron meteorite and furthers our knowledge of the phase composition changes in a fast-cooled iron meteorite below 400 °C. We demonstrate that APT in conjunction with TEM is a useful approach to study the major, minor, and trace elemental composition of nanoscale features within fast-cooled iron meteorites.