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SIMS Analysis of Lead Isotopes in the Primary Ore Body of the Koongarra Deposit, Australia: Behavior of Lead in the Alteration of Uranium Minerals

Published online by Cambridge University Press:  10 February 2011

H. Isobe ,
H. Hidaka  and
T. Ohnuki
H. Isobe
Affiliation:
Dept. of Environ. Safety Res., JAERI, Tokai, Ibaraki 319-11, Japan
H. Hidaka
Affiliation:
Dept. of Earth Planet. Sys. Sci., Hiroshima Univ., Higashi-Hiroshima 739, Japan
T. Ohnuki
Affiliation:
Dept. of Environ. Safety Res., JAERI, Tokai, Ibaraki 319-11, Japan
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Abstract

Lead, the final decay product of uranium, is found in natural uranium ore deposits. The isotope composition of lead in uranium-bearing minerals reflects their age and the migration behavior of lead. Secondary Ion Mass Spectroscopy (SIMS) can be used to analyze the isotopic composition of minerals. SIMS analysis of lead contained in the Koongarra uranium deposit, Australia, revealed that uraninite and uranyl minerals with different chemical composition in the primary ore region have homogeneous lead isotope, from the highest grade area to a uranyl silicate zone at a distance of 6.1m. Uranyl minerals, which have good crystallinity and retain stoichiometric composition, have “old” lead isotope composition identical to that of uraninite. Uranyl minerals keep exchanging lead with ground water in the primary ore region through metamictization and recrystallization by alpha-decay damage. Sulfide minerals just outside the primary ore body contain only radiogenic lead with an isotopic composition different from that of uranium minerals. Lead that migrated from the primary ore body formed sulfide minerals in a specific geological event. Since then, lead produced from uranium decay has been retained in the primary ore body, in spite of recrystallization of uranyl minerals and exchange and homogenization of lead isotopes. Uranium minerals may retain minor elements despite intense alpha-decay dose.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 506: Symposium – Scientific Basis for Nuclear Waste Management XXI , 1997 , 687
Copyright
Copyright © Materials Research Society 1998

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References

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