| Title | Geochemical Assessment of the Picard River Geothermal Prospect in Northern Dominica |
|---|---|
| Authors | Kenneth B. Alexander, Scott W. Herman, Andrew P.G. Fowler |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | This paper discusses the methods and results of a geochemical survey conducted in April-May 2024 as part of a supplemental resource assessment of the Picard River prospect in northern Dominica. The work is part of several programs funded by the NZ Caribbean Facility for Renewable Energy (FRENZ), which is supported by the Ministry of Foreign Affairs (MFAT). Fieldwork involved geological and geochemical surveys, including innovative techniques such as sampling of submarine hot springs and multicomponent thermodynamic geothermometry (MTG). The FRENZ technical team collected water samples from terrestrial and submarine hot springs. The submarine springs, which discharged water at temperatures between 124-128°C, were sampled at depths between 25 and 28 m. This is essentially equivalent to pressure in a >30-m deep borehole onshore that follows the boiling point with depth curve. As such, the submarine springs provide the most valid sampling points of the Picard River geothermal system reservoir outflow. The FRENZ technical team successfully removed the seawater component from the submarine water samples using geochemical modeling software. This approach yielded a high-quality MTG analysis, providing a more precise range of reservoir temperatures for the submarine springs. The new range spans approximately 220 to 240°C, significantly narrowing the previous range of 163 to 270°C, which was determined based on classical geothermometry analysis on diluted terrestrial spring water samples collected in 2009. The geochemical analytical results of the water samples, both historical and current, indicate three different water types, consistent with the hydrological model typical of a high-elevation, andesitic island-arc hydrothermal system. |