Chemical Processes Governing Siloam And Tshipise Geothermal Springs, Limpopo Province, South Africa

Geothermal springs occur throughout the world and South Africa (SA) is endowed with several springs of this nature. Siloam and Tshipise are among the known scalding geothermal springs found in Limpopo Province. The optimal use of a geothermal spring is largely dependent upon its physical and chemical characteristics. Hence, there is need to understand the chemical processes controlling the springs. Hydrochemical characteristics of Siloam and Tshipise geothermal springs were undertaken for a period of six months May – December 2014. Water samples were collected from the springs and stored at low temperatures (+/- 4 °C) for analysis of hydrochemical characteristics. The results show that Siloam and Tshipise geothermal spring water is not suitable for drinking and irrigation due to high pH, high fluoride concentrations, high sodium absorption ratio (SAR), Residual sodium carbonate (RSC) and permeability index (PI) values. The water type found in Siloam and Tshipise were Na-Cl and Na-HCO3, respectively. The variations were probably due to the differences in fundamental changes in water chemistry and the geology. Plot (Ca+Mg) vs (HCO3+SO4) shows the distribution of geothermal water between silicate and carbonate weathering processes. The chloro-alkaline indices (CAI) 1, 2 calculated from the waters of the study area give negative values and this implies the presence of base-exchange reaction. Hence, sources of the geothermal springs were deep and could not significantly be affected by rainfall recharge. Therefore, major processes controlling the water quality are silicate weathering, mineral dissolution, cation exchange and inverse cation exchange.