Geological setting and hydrogeothermal characteristics of the Kapong non-volcanic hot spring area in Southern Thailand

Abstract

Thailand is well known for its hot springs, altogether more than 112; all of them are related to non-volcanic geological settings. Currently most hot springs are used as spas; however, for any further development a better understanding of the subsurface geological settings and hydrogeothermal characteristics is. The Kapong hot spring system, located in the northwestern part of Southern Thailand with exit temperatures of maximal 78 °C and flow rates of 1.5–2.0 L/s, is presented here as an example and as a case study for similar investigations in Thailand and for countries having non-volcanic geothermal systems. Geological investigations were combined with aeromagnetic data for the delineation of Mesozoic igneous bodies. Shallower (1D, 2D) and deeper (magnetotelluric) resistivity surveys, down to 2000 m, were carried out for the characterization of shallow aquifers and fluid pathways. Geochemical water analyses, isotope studies, and geothermometer calculations provided evidence for the source and pathways of the hot spring waters, as well for the geothermal reservoir temperature. Results show that meteoric water is flows downwards and heats up by radioactive decay in the igneous bodies. Intersections of fractures and faults related to a nearby major fault zone provide the main pathways for the meteoric water to descend downwards and particularly for hot water to flow upwards. Further steps will be taken to identify the potential of the Kapong hot spring site for electricity generation via low enthalpy technology; possible demand sides are less than 50 km in the west with international tourist destinations along the Andaman coastline.