Unveiling the hidden heat potentiality of the caledonian and mourne granites, Northern Ireland: A geochemical recalibration of suppressed airborne radiogenic heat signals

Airborne Gamma-Ray Spectrometry (AGRS) serves as an essential tool for geothermal exploration; nevertheless, its efficiency in peat-covered, till (glacial deposits), and high-moisture soils remains poorly quantified. This study investigates one such example and assesses the discrepancy between airborne-derived Radiogenic Heat Production (RHP) and bedrock geochemistry of the Caledonian and Mourne granites in Northern Ireland. The utilised dual analysis approach (Rybach in 1988 and Carmichael in 1989) indicated that a considerable surface attenuation due to the saturated organic overburden masks the actual capacity of RHP. This is evidenced by the determined low median RHP values of 0.9 µW m –3 (σ± 0.27) and 2.4 µW m –3 (σ± 0.80) for Caledonian and Mourne granites, respectively. Analysis of published whole-rock geochemical data of the Mourne suite contributed to addressing this environmental interference and facilitated the determination of correction factors (CF), enabling the reclassification of Mourne granites. For instance, the derivational regional CF =2.52 resulted in a median RHP of 6.3 µW m –3 (σ± 2.3), significantly categorising Mourne granites as a high heat-producing granite. Moreover, applying this CF to the Caledonian granites yields an average RHP of 2.27 µW m –3 (σ± 0.68), precisely reflecting its bedrock characteristics and highlighting a significant regional tendency to underestimate geothermal resources by >50%. These results prove that existing regional RHP maps in peat-covered, glacial and high-moisture regions are notably underestimated and provide a transferable workflow for recalibrating airborne surveys to identify concealed high-heat content targets.