3-D magnetotelluric modeling and radiogenic heat reservoir for EGS development: A case study of the Kestanbol Granitoid intrusion (NW Türkiye)

Enhanced Geothermal Systems (EGS) provide firm, low-carbon baseload power and can contribute to reducing fossil-fuel-based energy generation. Granites and granitoids are particularly favourable EGS hosts due to their widespread occurrence, fracture-controlled permeability, and long-term heat supply from radiogenic decay. This study proposes an EGS development plan for the Kestanbol Granitoid Intrusion (KGI) in NW Anatolia, T & uuml;rkiye, based on a three-dimensional magnetotelluric (MT) model integrated with geochemical constraints on radiogenic heat production (RHP). We invert MT data acquired at fifty unevenly spaced sites to image the 3D resistivity structure of the KGI and its surroundings, resolving a highly resistive plutonic body bounded by relatively conductive fault-fracture zones. To quantify the radiogenic heat reservoir, we determine RHP rates from uranium, thorium, and potassium concentrations measured on twenty-seven rock samples from the KGI and adjacent lithologies, and integrate these values with the MT-derived pluton geometry. When combined with the regional stress regime, the integrated results indicate that the KGI hosts elevated RHP relative to surrounding rocks and that its internal structure and fault-controlled permeability architecture are favourable for EGS development. In particular, the north-western margin of the KGI emerges as the most promising target for injection-production well pairs. This workflow demonstrates how integrated MT, geochemical, and structural analyses can provide a quantitative, site-specific basis for EGS prospect ranking and drilling strategy in radiogenic granite/granitoid provinces. Overall, we propose a site-specific and risk-aware EGS development plan for the KGI that couples subsurface structure, radiogenic heat supply, and permeability architecture, providing a transferable framework for assessing radiogenic granite/granitoid provinces.