Airborne Radiometric Data Assessment and Comparison with Topsoil Geochemical U, Th and K

Tellus Border is an EU INTERREG IVA-funded cross-border project which now has newly-acquired airborne geophysical and geochemical data in the six border counties of the Republic of Ireland. This extensive regional baseline geophysical and geochemical dataset provides an excellent opportunity to investigate the relationship between measured radiometric data and equivalent geochemical topsoil concentrations of uranium (U), thorium (Th) and potassium (K). Exploratory data analyses and univariate statistical summaries of both datasets (geophysical and geochemical) were compared across the whole survey area and then by different geological unit and soil type. This allowed trends between different elements and different units to be investigated. Good agreement was found between airborne and topsoil Thorium and Uranium values with similar distributions, means and medians. These values remain generally consistent between different geological units, however, Potassium (k) geochemical values differ significantly with airborne values, being on average 6 times lower. The best agreement between K values occurs over low-K geological regions such as from limestones and shales within carboniferous sediments. High-K regions such as over K-feldspar rich granites show the greatest divergence between geophysical and geochemical data. Generally strong geogenic controls are seen throughout all of the datasets.