| Title | Geologic controls on geothermal system location and type |
|---|---|
| Authors | I.C. Wallis, J.V. Rowland, D.E. Dempsey |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | global review, structural controls, volcanic controls, system localization, The Great Basin, Ireland Rift System, Taupo Rift Zone, East African Rift System, |
| Abstract | We evaluate five productive geothermal regions to determine the district-scale geologic controls on the distribution of conventional geothermal resources that are suitable for development. The regions included are the East African Rift System, the Great Sumatra Fault in Indonesia, the Iceland Rift System, the Taupo Volcanic Zone in New Zealand, and the Great Basin in the USA. This study expands our previous work that focused on the structural context by evaluating the distribution of volcanism. There is an unequivocal global- and district-scale relationship to volcanism that is reflected in both the type of geothermal system and their spatial distribution. However, our case studies highlight that the presence of recent volcanism does not guarantee localisation of a developable resource. A structural and tectonic setting that enables highflux fluid flow is also required. We propose a classification system for geothermal resources that expands the common categories of volcanic (arc and rifttype) and deep circulation (magmatic and amagmatic) by including the temporal and spatial distance to a volcanic heat source. The distance to heat source has implications for the temporal stability of the geothermal anomaly, as evidenced by the degree of mineral disequilibrium. This classification system improves analogue selection, provides a framework for comparative studies, and highlights the diverse range of geothermal resources that can be developed. |