Uranium (U) concentration and the activities of ²³⁸U, ²³⁴U, and ²³⁰Th were determined for groundwaters, spring waters, and lake water collected from the Shihongtan sandstone-hosted U ore district and in the surrounding area, NW China. The results show that the groundwaters from the oxidizing aquifer with high dissolved oxygen concentration (O₂) and oxidation-reduction potential (Eh) are enriched in U. The high U concentration of groundwaters may be due to the interaction between these oxidizing groundwaters and U ore bodies, which would result in U that is not in secular equilibrium. Uranium is re-precipitated as uraninite on weathered surfaces and organic material, forming localized ore bodies in the sandstone-hosted aquifer. The ²³⁴U/²³⁸U, ²³⁰Th/²³⁴U, and ²³⁰Th/²³⁸U activity ratios (ARs) for most water samples show obvious deviations from secular equilibrium (0.27–2.86), indicating the presence of water-rock/ore interactions during the last 1.7 Ma and probably longer. The ²³⁴U/²³⁸U AR generally increases with decreasing U concentrations in the groundwaters, suggesting that mixing of two water sources may occur in the aquifer. This is consistent with the fact that most of the U ore bodies in the deposit have a tabular shape originati from mixing between a relatively saline fluid and a more rapidly flowing U-bearing meteoric water.

The Chisel Lake deposit, in the Flin Flon – Snow Lake Mineral Belt in northern Manitoba, is characterized by an ore mineral assemblage dominated by pyrite and sphalerite, with minor chalcopyrite, galena, and pyrrhotite and trace amounts of other Cu-, Fe-, Sb-, Sn-, As-, Ni-, and Ag-bearing sulfides. Silver is hosted in a variety of Ag-bearing sulfides (chalcopyrite and freibergite–argentotennantite series) and its own sulfide (acanthite). The major elements chemical compositions of the ore sulfides define two populations of sphalerite (Fe-rich and Fe-poor), three populations of chalcopyrite (pure, Ag-rich, and Ag- and Sb-rich), and a typical galena, in addition to pyrite and pyrrhotite. Trace elements are dominated by Mn and Cd for sphalerite; Sn, Zn, and Ge for chalcopyrite; Se and Ni for pyrrhotite; and As and Co for pyrite. Formation temperature was best estimated, from the Fe and trace elements (Ga, Ge, Mn, and In) concentrations in sphalerite, at approximately 340 °C, with other methods giving less reliable temperature and pressure estimates.

Projects involving deep geological disposal of nuclear waste are unique in that predictive models of long-term safety often involve geological timeframes. This manuscript provides a review of natural and anthropogenic analogues for high-level nuclear waste disposal in a deep geological repository. We also occasionally highlight analogues that have been used for low- and intermediate-level waste. Most studies define natural analogues as either naturally occurring or anthropogenic systems. In this paper, we distinguish between natural analogues and anthropogenic analogues because the latter generally provide non-technical (anecdotal) illustrations of concepts and processes for the safety case, whereas the former can provide technical and quantitative information. In addition, natural analogues can provide information over geological time scales (millions of years) and spatial scales (kilometers), whereas anthropogenic analogues provide information over a much more limited time scale (hundreds or thousands of years). Regardless of the definition, analogue studies provide one of the multiple lines of evidence intended to increase confidence in the safe geological disposal of high-level nuclear waste. They are deemed necessary because they complement the experiments that are carried out over a period of months or years. They also provide a way to validate numerical long-term safety assessment models with information and data covering geological time scales and spatial scales. The first part of this review describes the analogue concept. The second and third parts provide examples of natural and anthropogenic analogues for engineered barrier systems and natural barriers. Part four describes analogues for complex coupled transport processes. Finally, we discuss general and specific areas of future research. A concerted effort should be made to ensure that there is a transfer of data from the complex, natural analogue field studies to simplistic models which, by necessity, are used to evaluate the long-term safety of deep geological repositories. Field analogue studies should be planned to interface with laboratory experiments and, ultimately, with in situ field experiments, when the final repository site is selected. This will involve using natural analogue data in a quantitative way to support the deep geological repository safety case.