Thermal induced micro-structural changes of geological samples at the nanoscale

The Callovian–Oxfordian mudstone (COx) is a key geological formation being evaluated for deep geological radioactive waste disposal in France due to its low permeability and favorable retention properties. This study investigates the impact of thermal gradients on the nano-structure of COx mudstone samples, particularly focusing on fracture development and its relation to mineral composition. Samples were subjected to a controlled thermal gradient ranging from ambient temperature to 200°C. At each 20°C increment, the samples underwent high-resolution nano-tomography scanning with a pixel size of 50 nm. The resulting data provided detailed three-dimensional images of the mudstone's internal structure, allowing for precise quantification of nano-structural changes.