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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

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1945-3027
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Volume 88, Issue 10

Issues

Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon

Mostafa Fayek
  • Corresponding author
  • Geological Sciences, University of Tennessee, Knoxville, Tennessee 37996, U.S.A.
  • Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, Tennessee 37831, U.S.A.
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/ Satoshi Utsunomiya
  • Nuclear Engineering and Radiological Sciences and Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104, U.S.A.
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/ Rodney C. Ewing
  • Nuclear Engineering and Radiological Sciences and Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104, U.S.A.
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/ Lee R. Riciputi
  • Geological Sciences, University of Tennessee, Knoxville, Tennessee 37996, U.S.A.
  • Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, Tennessee 37831, U.S.A.
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/ Keld A. Jensen
  • Nuclear Engineering and Radiological Sciences and Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104, U.S.A.
  • National Institute of Occupational Health, Denmark, DK-2100 Copenhagen
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Published Online: 2015-03-31 | DOI: https://doi.org/10.2138/am-2003-1021

Abstract

High spatial resolution (10-30 μm), in situ oxygen isotopic analyses by secondary ion mass spectrometry (SIMS), coupled with high-resolution transmission electron microscopy (HRTEM), were used to show that uraninite from the Oklo-Okélobondo natural fission reactors that occur in near surface environments, have low δ18O values and nanotextures that are consistent with interaction with ground water. These low δ18O values (-14.4 to -8.5‰) suggest that the minerals exchanged with meteoric groundwater. In contrast, reactor zones that occur at depth have largely retained their original O isotopic composition (-10.2 to -5.6‰) and uraninites are well-crystallized and essentially defect-free. These observations clearly demonstrate that by combining both HRTEM and in situ O isotopic analyses by SIMS, it is possible to characterize the nano-scale porosity and postdepositional alteration of U-bearing phases.

About the article

Received: 2003-01-13

Accepted: 2003-06-08

Published Online: 2015-03-31

Published in Print: 2003-10-01


Citation Information: American Mineralogist, Volume 88, Issue 10, Pages 1583–1590, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2003-1021.

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© 2015 by Walter de Gruyter Berlin/Boston.

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