Geochemistry and geothermometry of non-volcanic hot springs in West Malaysia

Abstract

Although more than sixty hot springs have been reported in West Malaysia, their geochemistry, geothermometry and utilization as a potential energy source have not been considered yet. This study reports the geochemistry, geothermometry and mineral saturation indices of a number of hot springs in West Malaysia. The potential of these hot springs as a source of geothermal energy as well as their origin and possible mixing with surface cold waters have been discussed.Surface temperatures of the studied hot springs range from 41 to 99°C and pH values vary between 5.5 and 9. Geochemical data showed that among cations, Si, Na, Ca and K occur in relatively high contents, while Mg and Fe show very low concentrations. On the other hand, HCO3 is present in relatively high concentration compared to other anions (SO4, Cl and F). Data also illustrated that most of the studied hot springs are K–Na–bicarbonate rich waters although they represent different geological provenances in West Malaysia reflecting homogeneity in the geological formations and/or hydrochemical processes governing the characteristics of these waters. This homogeneity also indicates the insignificant effect of local geology on the chemistry of the studied hot springs. Saturation indices calculations of the studied thermal waters indicate that most of the secondary mineral phases such as goethite and hematite are apparently supersaturated while quartz and chalcedony are saturated. Conversely, amorphous silica is slightly under-saturated. These results suggest similar rock–water interactions for both geothermal and non-geothermal waters.The geological settings of the studied hot springs either in or close to granitic masses or along the major fault or shear zones as well as the Na-bicarbonate nature of the waters and low sulfate concentrations suggest their non-volcanic origin. They are also similar in their geological setting and water chemistry to other non-volcanic hot springs in other parts of the world. However, the possible mixing of the original hot waters with near surface cold water is evident from the clear disagreement between the silica and cation geothermometers as well as the disequilibrium with their associated host rocks as indicated from the plot of studied hot springs in the Na–K–Mg ternary diagram and saturation indices calculations.Quartz geothermometers gave equilibrium temperatures ranging from 93°C in the Ayer Hangat hot spring to 154°C in the Lojing hot spring. This requires 398 to 649kJ/kg energy to heat the water suggesting an intermediate enthalpy. These results also pointed out that some of the studied hot springs have potential to generate adequate heat, which could be harnessed for energy generation upon further work to prove their viability.