Spatial Stability and Integrity of Montmorillonite for Robust Assessment of Long-Term Climate Driven Scenarios (MORO)

Introduction

In this project, we aim to increase the robustness of montmorillonite stability assessment at disposal site by increasing the spatial understanding of smectite occurrence across Finland. The central research question is: are there regional controls for late-stage alteration, or is it primarily controlled by local factors?

To address this question, we require more information on:
• How much and where we have smectites? (fracture fillings vs. pervasive alteration)
• How old are they (structural control and genesis)?
• Is there any clear variation with depth, relevant to disposal, that might be climate controlled (e.g. glaciations or permafrost)
• Are there any water-rock interaction related controls in their composition? (current vs. palaeo groundwater systems)

Further, related to the last bullet, it is of interest to assess the exchangeable cation composition of these clays (e.g. Ca- and Na-montmorillonite), due to their differing erodibility properties. In addition, new Information obtained for all smectites can be useful for buffer stability considerations in the long-term (also for scenarios where mineral alteration may happen).

The project integrates advanced analytical techniques, geospatial modelling, and geochronology by including:
• Cross-disciplinary approach combining geology, hydrogeology, geochemistry, and data science
• Novel application of hyperspectral imaging analysis, including machine learning tools, to identify smectites and other fracture filling minerals from the drill core data sets, and utilising machine learning for mineral mapping
• Development and application of advanced dating methods for fracture-filling smectites, applying novel approaches related to REE minerals
• Integration of near-surface analogues to assess depth-dependant process effects (e.g. groundwater chemistry changes and permafrost)

This project addresses critical challenges related to the long-term safety of nuclear waste disposal, with a focus on fault architecture and fracture minerals, particularly on the behaviour of smectite clays (e.g., montmorillonite) under evolving environmental conditions. This research aligns closely with the objectives outlined in SAFER2028 Framework Plan, particularly in advancing the understanding of engineered barrier systems (EBS) stability and groundwater interactions.

The coordinator of the project: GTK

Funding authority: SAFER2028

Contact person: Heini Reijonen

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