Tetravalent uranium in calcite
X-ray absorption spectroscopy and x-ray fluorescence microprobe studies of 35-million-year-old calcite from a Mississippi Valley-type zinc ore deposit indicate substitution of tetravalent uranium for divalent calcium. Thus, tetravalent uranium has a stable location in calcite deposited under reducing conditions. This result validates uranium-series dating methods (including uranium/lead dating) for ancient calcite and shows that calcite provides a sink for uranium in deep groundwater aquifers and anoxic lacustrine and marine basins.
N. C. Sturchio, M. R. Antonio, L. Soderholm, Argonne National Laboratory, Argonne, IL 60439, USA. S. R. Sutton, Consortium for Advanced Radiation Sources and Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA.
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Sturchio
MR
Antonio
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Soderholm
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Sutton
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Brannon