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  • 1
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    Heavy nitrogen in carbonatites of the kola peninsula: A possible signature of the deep mantle (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2000-01-05
    Beschreibung: Nitrogen and argon isotopes were measured in carbonatites and associated rocks from the Kola Peninsula in Russia. The Kola mantle source, which is thought to be located in the deep mantle, is enriched in heavy nitrogen (+3 per mil relative to air) as compared to Earth's surface (atmosphere and crust, +2 per mil) and the shallow mantle (-4 per mil). Recycling of oceanic crust (+6 per mil) or metal-silicate partitioning may account for the nitrogen isotopic composition of the deep mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dauphas -- Marty -- New York, N.Y. -- Science. 1999 Dec 24;286(5449):2488-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre de Recherches Petrographiques et Geochimiques, CNRS UPR 9046, 15 rue Notre-Dame des Pauvres, Boite Postale 20, 54501 Vandoeuvre-les-Nancy Cedex, France. Ecole Nationale Superieure de Geologie, rue du doyen Marcel Roubault, Boit.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10617459" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 2
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    Iron isotope fractionation during magmatic differentiation in Kilauea Iki lava lake (2008)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2008-06-21
    Beschreibung: Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stagemeltveins are 0.2 permil (per thousand) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2 per thousand lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Teng, Fang-Zhen -- Dauphas, Nicolas -- Helz, Rosalind T -- New York, N.Y. -- Science. 2008 Jun 20;320(5883):1620-2. doi: 10.1126/science.1157166.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA. fteng@uark.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18566283" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 3
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    Clues from Fe isotope variations on the origin of early Archean BIFs from Greenland (2004)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2004-12-18
    Beschreibung: Archean rocks may provide a record of early Earth environments. However, such rocks have often been metamorphosed by high pressure and temperature, which can overprint the signatures of their original formation. Here, we show that the early Archean banded rocks from Isua, Akilia, and Innersuartuut, Greenland, are enriched in heavy iron isotopes by 0.1 to 0.5 per mil per atomic mass unit relative to igneous rocks worldwide. The observed enrichments are compatible with the transport, oxidation, and subsequent precipitation of ferrous iron emanating from hydrothermal vents and thus suggest that the original rocks were banded iron formations (BIFs). These variations therefore support a sedimentary origin for the Akilia banded rocks, which represent one of the oldest known occurrences of water-laid deposits on Earth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dauphas, Nicolas -- van Zuilen, Mark -- Wadhwa, Meenakshi -- Davis, Andrew M -- Marty, Bernard -- Janney, Philip E -- New York, N.Y. -- Science. 2004 Dec 17;306(5704):2077-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Origins Laboratory, Department of the Geophysical Sciences, and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA. dauphas@uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15604404" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 4
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    Low pCO2 in the pore water, not in the Archean air (2011)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2011-06-04
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dauphas, N -- Kasting, J F -- England -- Nature. 2011 Jun 2;474(7349):E2-3; discussion E4-5. doi: 10.1038/nature09960.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637, USA. dauphas@uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21637211" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere/*chemistry ; Carbon Dioxide/chemistry ; Earth (Planet) ; Environmental Microbiology ; Geologic Sediments/chemistry
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 5
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    Geochemistry: Sulphur from heaven and hell (2013)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2013-09-06
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dauphas, Nicolas -- England -- Nature. 2013 Sep 12;501(7466):175-6. doi: 10.1038/nature12554. Epub 2013 Sep 4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24005322" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 6
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    Hf-W-Th evidence for rapid growth of Mars and its status as a planetary embryo (2011)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2011-05-27
    Beschreibung: Terrestrial planets are thought to have formed through collisions between large planetary embryos of diameter approximately 1,000-5,000 km. For Earth, the last of these collisions involved an impact by a Mars-size embryo that formed the Moon 50-150 million years (Myr) after the birth of the Solar System. Although model simulations of the growth of terrestrial planets can reproduce the mass and dynamical parameters of the Earth and Venus, they fall short of explaining the small size of Mars. One possibility is that Mars was a planetary embryo that escaped collision and merging with other embryos. To assess this idea, it is crucial to know Mars' accretion timescale, which can be investigated using the (182)Hf-(182)W decay system in shergottite-nakhlite-chassignite meteorites. Nevertheless, this timescale remains poorly constrained owing to a large uncertainty associated with the Hf/W ratio of the Martian mantle and as a result, contradicting timescales have been reported that range between 0 and 15 Myr (refs 6-10). Here we show that Mars accreted very rapidly and reached about half of its present size in only 1.8(+0.9)(-1.0) Myr or less, which is consistent with a stranded planetary embryo origin. We have found a well-defined correlation between the Th/Hf and (176)Hf/(177)Hf ratios in chondrites that reflects remobilization of Lu and Th during parent-body processes. Using this relationship, we estimate the Hf/W ratio in Mars' mantle to be 3.51 +/- 0.45. This value is much more precise than previous estimates, which ranged between 2.6 and 5.0 (ref. 6), and lifts the large uncertainty that plagued previous estimates of the age of Mars. Our results also demonstrate that Mars grew before dissipation of the nebular gas when approximately 100-km planetesimals, such as the parent bodies of chondrites, were still being formed. Mars' accretion occurred early enough to allow establishment of a magma ocean powered by decay of (26)Al.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dauphas, N -- Pourmand, A -- England -- Nature. 2011 May 26;473(7348):489-92. doi: 10.1038/nature10077.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA. dauphas@uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21614076" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 7
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    A nucleosynthetic origin for the Earth’s anomalous 142Nd composition (2016)
    Springer Nature
    In: Nature
    Details
    Publikationsdatum: 2016-09-15
    Beschreibung: A nucleosynthetic origin for the Earth’s anomalous 142Nd composition Nature 537, 7620 (2016). doi:10.1038/nature18956 Authors: C. Burkhardt, L. E. Borg, G. A. Brennecka, Q. R. Shollenberger, N. Dauphas & T. Kleine A long-standing paradigm assumes that the chemical and isotopic compositions of many elements in the bulk silicate Earth are the same as in chondrites. However, the accessible Earth has a greater 142Nd/144Nd ratio than do chondrites. Because 142Nd is the decay product of the now-extinct 146Sm (which has a half-life of 103 million years), this 142Nd difference seems to require a higher-than-chondritic Sm/Nd ratio for the accessible Earth. This must have been acquired during global silicate differentiation within the first 30 million years of Solar System formation and implies the formation of a complementary 142Nd-depleted reservoir that either is hidden in the deep Earth, or lost to space by impact erosion. Whether this complementary reservoir existed, and whether or not it has been lost from Earth, is a matter of debate, and has implications for determining the bulk composition of Earth, its heat content and structure, as well as for constraining the modes and timescales of its geodynamical evolution. Here we show that, compared with chondrites, Earth’s precursor bodies were enriched in neodymium that was produced by the slow neutron capture process (s-process) of nucleosynthesis. This s-process excess leads to higher 142Nd/144Nd ratios; after correction for this effect, the 142Nd/144Nd ratios of chondrites and the accessible Earth are indistinguishable within five parts per million. The 142Nd offset between the accessible silicate Earth and chondrites therefore reflects a higher proportion of s-process neodymium in the Earth, and not early differentiation processes. As such, our results obviate the need for hidden-reservoir or super-chondritic Earth models and imply a chondritic Sm/Nd ratio for the bulk Earth. Although chondrites formed at greater heliocentric distances and contain a different mix of presolar components than Earth, they nevertheless are suitable proxies for Earth’s bulk chemical composition.
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Springer Nature
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  • 8
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    Evidence of presolar SiC in the Allende Curious Marie calcium–aluminium-rich inclusion (2020)
    Springer Nature
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    Publikationsdatum: 2020
    Digitale ISSN: 2397-3366
    Thema: Physik
    Publiziert von Springer Nature
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  • 9
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    Origin of uranium isotope variations in early solar nebula condensates (2016)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2016-03-06
    Beschreibung: High-temperature condensates found in meteorites display uranium isotopic variations ( 235 U/ 238 U), which complicate dating the solar system’s formation, the origin of which remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide 247 Cm ( t 1/2 = 15.6 My) into 235 U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of 235 U reaching ~6% relative to average solar system composition, which can only be due to the decay of 247 Cm. This allows us to constrain the 247 Cm/ 235 U ratio at solar system formation to (1.1 ± 0.3) x 10 –4 . This value provides new clues on the universality of the rapid neutron capture r -process of nucleosynthesis.
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
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    Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2017-09-22
    Beschreibung: Earth exhibits a dichotomy in elevation and chemical composition between the continents and ocean floor. Reconstructing when this dichotomy arose is important for understanding when plate tectonics started and how the supply of nutrients to the oceans changed through time. We measured the titanium isotopic composition of shales to constrain the chemical composition of the continental crust exposed to weathering and found that shales of all ages have a uniform isotopic composition. This can only be explained if the emerged crust was predominantly felsic (silica-rich) since 3.5 billion years ago, requiring an early initiation of plate tectonics. We also observed a change in the abundance of biologically important nutrients phosphorus and nickel across the Archean-Proterozoic boundary, which might have helped trigger the rise in atmospheric oxygen.
    Schlagwort(e): Geochemistry, Geophysics
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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