Bulletin of the Geological Society of Malaysia, Volume 68, December 2019, pp. 109 – 115
Nur Islami*, Mitri Irianti
Physics Education, FKIP, Universitas Riau. Jl. HR. Soebrantas, Km. 12.5, Pekanbaru, 28293, Indonesia
* Corresponding author email address: firstname.lastname@example.org
Abstract: The first study of the hydrothermal system through the geophysical image in the area of Rokan Hulu hot spring is presented in this paper. The research employed integrated geophysical survey methods which consist of a geomagnetic, geoelectrical resistivity, and very low frequency (VLF) survey. Direct surface resistivity measurement was proposed and used to obtain a correlation of geological conditions with subsurface resistivity values and to correlate with VLF data.
The geoelectrical resistivity survey used Wenner configuration, with a minimum electrode distance of 5 m. While the VLF survey was taken at every distance of 6 m. Magnetic surveys were carried out with a spacing of about 0.5 km and covered an area approximately 9 km2. The results show that there is relatively lower magnetic value zone (about 65 nT) at the hot spring and extends to the southwest. The geoelectrical resistivity shows the possibility of water accumulation with resistivity value less than 150 ohm.m in the zone around the hot spring. While the VLF surveys show more conductive value which indicate the zone of fracture occurs at some places along the low geomagnetic anomaly zones. The surface temperature of the hot spring is 59°C with a constant discharge of about 7 l/s. The hot spring location is connected by fractures to the lower magnetic value zone, which the source of water is coming from the relatively higher elevation of the river surrounding the Rokan intrusion.
Keywords: Geoelectrical resistivity, hot spring, magnetic, VLF, Rokan Hulu