The Entre-Sambre-et-Meuse (hereafter abbreviated to ESEM) Miocene cryptokarsts area (Southern Belgium) is regarded as a natural analogue of the Belgian project for geological disposal of high-level radioactive waste. Indeed, the host sediment of the Belgian project is clay and the ESEM natural analogue contains clay as a sedimentary infilling and as neoformed mineral phases (kaolinite and its hydrous counterpart, halloysite). The study focuses on two aspects involving clay and its isolation capacity.
a.- Argillaceous sediments bearing organic matter in the ESEM karsts contain well-preserved Miocene wood fragments; the potential role of overlying clay beds in this preservation is considered;
b.- Significant anomalies in rare earth elements (REE) - which are analogues of several actinides present in the high-level waste - provide relevant information on the mobilization and trapping of those elements, with relation to clay mineralogy and neoformation processes.
The study has a twofold scope. First, it is intended to demonstrate the efficiency of the long-term (ca 10 m.y.) isolation capacity of clay, with regard to easily hydrolysable wood components. Secondly, it focuses on the role played by clay minerals in "dynamic" processes, such as the mobilization of trace elements (including REE) during palaeoweathering.
1. Field work
2. Evaluation of the preservation state of organic matter
3. Geochemical and mineralogical study of clay and other relevant mineral phases
Funding SchemeCSC - Cost-sharing contracts