| Title | Baseline Geothermal Survey of Vanuatu: Recent Results from Ambrym and Tanna Islands |
|---|---|
| Authors | S. Bloomberg, M.Leodoro |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Vanuatu, geochemistry, springs, exploration, Tanna, Ambrym, developing nations |
| Abstract | Geothermal reservoirs are a potential energy alternative to the high cost and emissions of burning imported fossil fuels. In this study we describe the results of a survey undertaken on the islands of Ambrym and Tanna, Vanuatu. The key question for the survey was to identify whether the existing geological features (particularly hot springs) could confirm if there was any presence of a high-temperature geothermal reservoir. A mixture of quantitative and qualitative observations were employed to record and sample the features. Geothermal water samples were analysed by the New Zealand Geothermal Analysis Laboratory for major cations, anions and isotopes. The waters from Ambrym showed a chemical difference between the NW springs and SW springs. The SW springs were closely related to mixed seawaters with the NW springs being more closely related to a mixed bicarbonate water. Silica geothermometry indicated that no water on Ambrym had boiled during ascent. Contrary to Ambrym, the geochemical analysis of the SE Tanna waters indicate that they are either steam-fed condensates in acid-sulphate systems or neutral-chloride waters from deep reservoirs. Si and K/Mg geothermometry indicate that the waters are boiling during ascent, with one spring discharging from a hot (200oC+) aquifer. The survey illustrates that the hot springs from Ambrym are peripherally-heated and that there is not an exploitable hydrothermal reservoir present despite the large geothermal fluid discharge. On Tanna we find that there is a high temperature reservoir present however more comprehensive geochemical, geophysical, and remote-sensing assessments will be required to understand the exploitability of the Siwi calderas’ high-temperature geothermal reservoir. |