Geodynamic Heterogeneity in Back Arc Basins: Implications for Heat Flow Distribution and Geothermal Energy Potential.

Using the geodynamic model of Hasterock et al., (2022), Ball et al., (2025) observed that existing natural hydrothermal systems and associated geothermal power plants are distributed across 12 different geodynamic settings.  We observe based on the Hasterock classification only 18 out of 489 power plants (3.6%) are located within Back Arc Basins (BABs). This may lead to the conclusion that, at a global scale, BABs are not highly prospective. However, a much more detailed observation of the various tectonic settings at specific locations shows some incongruencies in the Hasterock geodynamic classification. For example, key power plants such as Larderello, Italy are in fact located in a BAB setting, not in a Volcanic Arc setting (Ball, 2022). At a local scale it is important to refine global models to account for younger deformation that overprint previous tectonic events.

With Larderello as an analogue, we explore the idea that other BABs could be increasingly perspective for geothermal resources if the geodynamic setting is correctly assessed, and the local tectonics is understood. BABs, are extensional basins, typically formed behind active or inactive volcanic arc on the overriding plates. BABs, are known to be associated with high heat flow, due to the interplay of mantle dynamics, slab processes and crustal extension. In this work, we review the first-order controls on heat flow within the Aegean and Tyrrhenian back arc systems. We point to the comprehension of how factors like rapid localization of thinning in the crust and lithospheric mantle impacts heat flow, coupled with sedimentary cover. In detail, we evaluate the role of accessory parameters, like hydrothermal fluids ascending along faults and fractures, the role of intrusions due to patrial melting in response to rapid thinning in the crust and mantle, localizing high heat flows spots and causing significant thermal heterogeneities.

The dynamic settings of BABs could offer intriguing geothermal opportunities, but their structural, magmatic and hydrological histories need to be better understood. BAB’s like the Tyrrhenian and Aegean may provide exceptional opportunities for power generation. Exploration in this geodynamic setting could benefit by using the exploration triangle, which organizes the geological assessment into a hierarchical sequence of tasks. This play-based approach focusses assessment from the geodynamic setting and can be applied at the geothermal systems, and reservoirs scale. Successful application could greatly assist in identifying future prospects for geothermal development,  successfully exploiting BAB’s for power generation.