『Abstract
Uranium ore is an essential material in the preparation of nuclear
fuel for civilian as well as military uses. Uranium is first extracted
from uranium-bearing minerals using a variety of reagents, and
is precipitated from solutions as yellow cake prior to isotope
enrichment processes. The disintegration of the former Eastern
Bloc in the 1990s and frequent unrest in the Middle East have
underscored the need for better characteriziing source uranium
ores for forensic and attribution purposes.
The world's major deposits of U occur in several distinctly different
geological environments. Fourteen principal types of U deposits
and rocks with elevated uranium contents are recognized with more
than 40 subtypes. Combining our own analysis and literature data,
we have amassed over 250 oxygen isotope data from 13 major U-producing
countries, which vary widely from -32 to +11‰. However, interpreting
the oxygen isotopic composition of uraninite in terms of the composition
of the fluid from which it precipitated, or interacted with, requires
knowledge of the fractionation factor and temperature of interactions,
which are not always available. Since each deposit type occurs
within a unique geologic setting and is generally formed from
chemically distinct fluids, the chemical compositions of the uranium
ores are also distinct: uranium deposits that form in igneous
rocks have higher trace element compositions relative to sandstone-hosted
deposits. Our data shows that one of the most useful techniques
for distinguishing between uranium ore is to use a combination
of δ18O values and rare-earth elements (e.g., La/Yb
ratios). These methods may allow investigators to trace uranium
ore back to the source.
Keywords: Uranium ore; Oxygen isotope; Global distribution; Rare
earth element; Forensic and attribution』
Contents
1. Introduction
2. Uranium deposits
2.1. Uranium geochemistry and mineralogy
2.1.1. Uranium geochemistry
2.1.2. Uranium mineralogy
2.2. Classification of uranium deposits in the world
3. The isotopic composition of fluids and isotope fractionation
factors
3.1. Potential sources of fluids involved in he formation
of uranium deposits
3.2. Isotopic fractionation factors for the assessment of fluids
involved in the formation of uranium-rich ore deposits
4. Methods of isotopic analysis
4.1. Conventional BrF5 analysis
4.2. SIMS analysis
4.3. TIMS
5. Distribution of oxygen isotopes of uranium ores
5.1. Geographical location
5.2. Deposit type
5.3. Uranium minerals
6. Nuclear forensics and uranium deposits: oxygen isotopes and
trace elements
7. Conclusions
Acknowledgments
References