Assessment of Geothermal Energy and Mineralization in Taftan Volcano Using Stable Isotopes in Water

Taftan is a stratovolcano, located about 100 km to the south-southeast of Zahedan, in south-east of Iran. Volcanic rocks are mainly composed of pyroclastic deposits with andesite, dacite, and rhyolite lava flows. Strong local hydrothermal alteration is widespread in Taftan. The volcano is currently in an active fumarolic stage as there are a few vents with fumarolic activities and a few hot springs in the youngest craters on the flanks of the volcano. Four water samples, taken from streams and hot springs were analyzed for stable isotopes and chemical compositions. D and 18O values of the surface water (stream water) are between 30. 0 and 35. 0‰ and between 5. 4 and 6. 4‰, respectively. D and 18O values for hot springs are between 25. 0 and 26. 0‰ and 2. 0% respectively. D and 18O values for the samples taken from streams fall close to the Global Meteoritic Water Line (GMWL) while 18O and D values for the hot springs are heavier, shifting from GMWL. Relatively high D and 18O values from the hot springs are interpreted here as the result of subsurface evaporation, suggesting presence of shallow-level hot waters with temperatures between 150°C and 220°C. Results of stable isotopes, fumarolic activities, presence of hot springs and strong local alteration all around the volcano are indicative of existence of active geothermal field and possible economic mineralization in Taftan area.