| Abstract |
Rungwe Volcanic Province (RVP) situated south of Mbeya town in SW Tanzania sits on the triple junction of the East African Rift System. The magma chamber of Ngozi volcano is acting as heat source for a high-temperature geothermal system with reservoir temperatures of more than 200°C in >2000m depth. Similarly, the Lake Natron-Oldoinyo Lengai area of Gregory Rift in north-eastern Tanzania has active volcano, which the temperatures at similar depths are expected to be higher. Both the two provinces are potentially sources of geothermal energy along East African Rift System. Geochemical studies indicate that the natural waters in the Gregory Rift are characterized low Arsenic but exceptionally high fluoride contents in cold springs (3-15 mg/l) and (15–70 mg/l), which discharges into Lake Natron at different spring discharge rates, ranging from 30 to over 400 l/s; these F-values exceed the WHO recommended values of 4mg/l. Thermal waters of Rungwe Volcanic Province on the other hand have high concentration of Arsenic, ranging from 48 to 640 ppb, but very low F values. On average thermal springs have up to 17 times WHO recommended As-values in drinking water. The thermal discharge at Songwe Valley ranges from 300l/s with surface temperatures above 70C, which is an indication of subsurface thermal activity. Using remote sensing it is evident that underground water in RVP percolates through the tectonically active fault network, gets heated and discharges these thermal fluids, which can be utilized for energy. |