Hydrogen isotope analysis of micro-scale apatite inclusions in Archaean zircon grains

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Abstract

<p>A novel study of <i>in situ</i> hydrogen isotope composition (δD) measurements of micron-scale apatite inclusions hosted in zircon crystals was carried out by lateral high-resolution secondary ion mass spectrometry. The host rock of zircon is a tonalite belonging to the Nuvvuagittuq Supracrustal belt, Canada, which is considered to be one of the oldest supracrustal belts of Hadean-Archean age. Uranium-lead dating of host zircon crystals yielded an age of 3636 ± 20 Ma, which is consistent with previously reported ages of this unit. The δD values were measured for seven apatite inclusions, and range from –225 to +65‰ (vs. SMOW). A negative correlation was observed between δD values and the <sup>18</sup>O<sup>−</sup>/<sup>1</sup>H<sup>−</sup> ratios of the examined apatite inclusions. This relationship can be explained by a mixing trend between the original hydrogen in the apatite inclusions and contamination from the analytical environment. The pristine δD value estimated for the apatite inclusion is +53 ± 60‰, which was clearly distinct from the δD value resulting from bulk rock analysis, –49 ± 2‰. The pristine δD value of the tonalitic magma source may provide new constraints on the formation of the primitive crust and/or the ocean of the early Earth.</p>

Journal

  • GEOCHEMICAL JOURNAL

    GEOCHEMICAL JOURNAL 52(6), 457-466, 2018

    GEOCHEMICAL SOCIETY OF JAPAN

Codes

  • NII Article ID (NAID)
    130007534754
  • NII NACSIS-CAT ID (NCID)
    AA00654975
  • Text Lang
    ENG
  • ISSN
    0016-7002
  • NDL Article ID
    029526139
  • NDL Call No.
    Z53-R488
  • Data Source
    NDL  J-STAGE 
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