| Abstract |
The chemical analysis of geothermal water require proper sample collection, analysis and presentation of the data. The interpretation and evaluation of all available information regarding the geochemistry are accomplished by the methods of Na-K-Mg ternary diagram, Cl-SO4-HCO3 ternary diagram, geothermometer, WATCH programme and Suffer 12.6.963 software. Data sample from Fljótin-Iceland are analysed pertaining to their geochemistry surface exploration and compared to selected data from Rungwe geothermal area from Tanzania. The geothermal fields differ according to volcanic activities, rocky types and mineral composition. Fljótin are low temperature geothermal field while Rungwe is classified as high temperature geothermal field at Ngozi-Songwe (northern system) and a low temperature field at Kiejo-Mbaka (southern system). The reservoir temperatures at Fljótin are estimated by Na-K-Mg ternary diagram in the range of 120°C -160°C and confirmed with geothermometers with temperature range from geothermometers; 74-136°C (chalcedony) and 64-158°C (Na/K). The mineral saturation stated were by calculated chalcedony temperature where calcite and anhydrite, are saturated but not precipitating while amorphous silica is under saturated. The estimated reservoir temperature at the Rungwe volcanic zone are 130-200°C by Na-K-Mg ternary diagram, which is in agreement with quartz and K/Mg geothermometers at a temperature range of 119-154°C and 106-252°C respectively. Detailed study in the Rungwe thermal fluid chemistry is required in order to be satisfied for direct or indirect use, due to its high concentration of CO2 which can affect the utilization of the fluid, both field has a penitential for geothermal utilization. Fljótin on the other hand can be used direct due to its low total dissolved elements and low temperature. |