Journal: Meteoritics & Planetary Science

Abbreviation

Meteorit Planet Sci.

Publisher

Allen Press

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ISSN

1086-9379
0026-1114
1945-5100

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Publications1 - 8 of 8
  • Experimental reproduction of tectonic deformation lamellae in quartz and comparison to shock-induced planar deformation features
    Item type: Journal Article
    Vernooij, Martine G.C.; Langenhorst, Falko (2005)
    Meteoritics & Planetary Science
    Planar features can develop in quartz during comparatively slow tectonic deformation and during very fast dynamic shock metamorphism. Despite their very different structural nature, tectonically induced deformation lamellae have sometimes been mistaken as shock-induced planar deformation features (PDFs). To understand the formation of deformation lamellae and to address the substantial differences between them and PDFs, we have conducted deformation experiments on single crystals of quartz in a Griggs-type apparatus, at a temperature of 800 °C, a confining pressure of 12 kbar, and a strain rate of 0.7–1.1 · 10−6. The deformed samples were analyzed with transmission electron microscopy (TEM) and compared to natural PDFs from the Ries Crater, Germany. TEM revealed that tectonic deformation lamellae are associated with numerous sub-parallel curved subgrain walls, across which the orientation of the crystal changes slightly. The formation of deformation lamellae is due to glide- and climb-controlled deformation in the exponential creep regime. In contrast, the PDFs in shocked quartz from the Ries are perfectly planar, crystallographically controlled features that originally represented amorphous lamellae. Due to post-shock annealing and hydrothermal activity they are recrystallized and decorated with fluid inclusions.
  • 3He, 20,21,22Ne, 14C, 10Be, 26Al, and 36Cl in magnetic fractions of cosmic dust from Greenland and Antarctica
    Item type: Journal Article
    Jull, A.J. Timothy; Lal, Devendra; Taylor, Susan; et al. (2007)
    Meteoritics & Planetary Science
    We report on studies of the concentrations of cosmogenic nuclides in the magnetic fraction of cosmic dust particles recovered from the South Pole Water Well (SPWW) and from Greenland. Our results confirm that cosmic dust material from these locations contains measurable amounts of cosmogenic nuclides. The Antarctic particles (and possibly those from Greenland as well) also contain minor amounts of solar Ne. Concentrations of cosmogenic nuclides are consistent with irradiation of this material as small objects in space, with exposure ages similar to the expected Poynting-Robertson (P-R) lifetimes of 50–200 kyr for particles 25–100 μm in size.
  • Palladium-Silver Isotope Systematics of the Ordinary Chondrite Allegan (H5) and the Acapulcoite Dhofar 125
    Item type: Other Conference Item
    Theis, Karen J.; Schönbächler, Maria (2012)
    Meteoritics & Planetary Science
  • He and Ne in individual chromite grains from the regolith breccia Ghubara (L5): Exploring the history of the L chondrite parent body regolith
    Item type: Journal Article
    Meier, Matthias M.M.; Schmitz, Birger; Alwmark, Carl; et al. (2014)
    Meteoritics & Planetary Science
    We analyzed He and Ne in chromite grains from the regolith breccia Ghubara (L5), to compare it with He and Ne in sediment-dispersed extraterrestrial chromite (SEC) grains from mid-Ordovician sediments. These SEC grains arrived on Earth as micrometeorites in the aftermath of the L chondrite parent body (LCPB) breakup event, 470 Ma ago. A significant fraction of them show prolonged exposure to galactic cosmic rays for up to several 10 Ma. The majority of the cosmogenic noble gases in these grains were probably acquired in the regolith of the LCPB (Meier et al. 2010). Ghubara, an L chondritic regolith breccia with an Ar-Ar shock age of 470 Ma, is a sample of that regolith. We find cosmic-ray exposure ages of up to several 10 Ma in some Ghubara chromite grains, confirming for the first time that individual chromite grains with such high exposure ages indeed existed in the LCPB regolith, and that the >10 Ma cosmic-ray exposure ages found in recent micrometeorites are thus not necessarily indicative of an origin in the Kuiper Belt. Some Ghubara chromite grains show much lower concentrations of cosmogenic He and Ne, indicating that the 4π (last-stage) exposure age of the Ghubara meteoroid lasted only 4–6 Ma. This exposure age is considerably shorter than the 15–20 Ma suggested before from bulk analyses, indicating that bulk samples have seen regolith pre-exposure as well. The shorter last-stage exposure age probably links Ghubara to a small peak of 40Ar-poor L5 chondrites of the same exposure age. Furthermore, and quite unexpectedly, we find a Ne component similar to presolar Ne-HL in the chromite grains, perhaps indicating that some presolar Ne can be preserved even in meteorites of petrologic type 5.
  • Making the Moon from the Earth's Mantle - The Geochemical Perspective
    Item type: Other Conference Item
    Meier, Matthias M.M.; Reufer, Andreas; Benz, W.; et al. (2011)
    Meteoritics & Planetary Science
  • Zirconium-Hafnium Evidence for Separate Synthesis of Light Neutron-Rich Nuclei
    Item type: Other Conference Item
    Akram, Waqas M.; Schönbächler, Maria; Sprung, Peter; et al. (2011)
    Meteoritics & Planetary Science
  • Potential Nucleosynthetic sources of the titanium isotope variations in solar system materials
    Item type: Other Conference Item
    Williams, N.H.; Fehr, Manuela; Akram, W.M.; et al. (2012)
    Meteoritics & Planetary Science
  • Micro-XCT chondrule classification for subsequent isotope analysis
    Item type: Journal Article
    Jäggi, Noah; Roth, Antoine S.G.; Rüfenacht, Miriam; et al. (2023)
    Meteoritics & Planetary Science
    Chondrules are microscopic, recrystallized melt droplets found in chondritic meteorites. High-resolution isotope analyses of minor elements require large enough element quantities which are obtained by dissolving entire chondrules. This work emphasizes the importance of X-ray computed tomography (XCT) to detect features that can significantly affect the bulk chondrule isotope composition. It thereby expands on other works by looking into chondrules from a wide range of chondrites including CR, CV, CB, CM, L, and EL samples before turning toward complex and time-consuming chemical processing. The features considered are metal and igneous rims, compound chondrules, matrix remnants, and metal contents. In addition to the identification of these features, computed tomography prevents the inclusion of non-chondrule samples (pure matrix or metal) as well as samples where two different chondrule fragments with potentially different isotope compositions are held together by matrix. Matrix surrounding chondrules is also easily detected and the affected chondrules can be omitted or reprocessed. The results strongly encourage to perform XCT before dissolution of chondrules for isotope analysis as a non-invasive method.
Publications1 - 8 of 8