| Abstract |
Geothermal exploration by mapping surface manifestations, which includes geological mapping, structural mapping and hydrothermal mapping was carried out in the four geothermal prospects of South-western Tanzania namely Songwe, Mapulo-Kasimulo, Rungwe and Lake Ngozi area. The major objective was to produce a hydrothermal map including phenomena like hot and warm grounds, hot and warm springs, steam vents, mud pits, geothermal altered rocks and any kind of surface thermal manifestation. For practical purposes hot springs, faults, major fractures and young volcanic features like volcanic craters, eruptive fissures and hot grounds were mapped as a link is often found to exist between tectonic features and the distribution of geothermal manifestations. During mapping surface temperatures of the hot ground, hot springs, lakes, rivers and stream were measured. The highest surface temperature of 98oC was registered at the Rungwe, 85oC at Songwe, 65oC at Mampulo-Kasimulo and around 65 oC at Lake Ngozi prospects respectively. The lake is a crater lake and the satellite imagery indicated some promising sources of heat. The water encountered is of HCO3 type and the underground temperature were estimated using Giggenbach ternary diagram; it showed a tkn temperature of 180oC at Mampulo, 210oC at Songwe, 220oC at Rungwe and Malonde. The estimation of heat stored in rocks, fluid, vapor and condensate was done. The potential usable heat was calculated and the result was used to estimate the Power Potential for Songwe which is 107MWe.These preliminary results are an indication that Tanzania has a potential for geothermal exploitation. |