Characterisation of the thermal aquifer associated with the Siloam hot spring in Limpopo, South Africa

Abstract

The Siloam hot spring is located on the Siloam fault in the northern Limpopo Province of South Africa. Geophysical data were collected over the aquifer hosting the spring with the aim of determining its physical characteristics. Regional airborne magnetic data provided information about structural features on a larger scale, allowing for the identification of number of dykes and faults, including the Siloam fault. Ground magnetic and electromagnetic surveys were collected in the area around the Siloam hot spring. The increased resolution of the ground magnetic data made it possible to delineate two east-west striking dykes, one to the north of the hot spring and one to the south. The dykes created impermeable barriers of the aquifer. Results of the electromagnetic survey showed that the hot spring is located on a very conductive zone that is roughly a 150 m wide. Combining the results of the ground and airborne geophysics gave a width of 150 m and a lateral extent of approximately 11500 m for the aquifer. The high conductivities associated with the spring suggest that the spring water may be mineralized. The impact of the thermal water on the environment and depth characteristics of the aquifer will need to be studied further.