Geochemical Investigation of Thermal Water Wells in Tebing Tinggi, North Sumatra, Indonesia: Geology and Preliminary Insights into Their Sources

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DOI:

https://doi.org/10.17794/rgn.2026.5.8

Keywords:

thermal water hydrogeochemistry, geothermometry, low-enthalpy geothermal system, fault fracture density, North Sumatra

Abstract

Tebing Tinggi is a small town in North Sumatra Province, located about 80 kilometres northwest of Medan, 80 kilometres southwest of the Toba Caldera, and 20 kilometres east of the coast. Founded in 1917 as a trading post for the local plantation industry, Tebing Tinggi evolved from a small village into a city between 1864 and 1917. As more Europeans settled in the town, numerous public facilities were constructed, including several drilled wells that naturally released thermal waters. Some of these wells, which are over 100 years old, are still in use. Samples were collected from several thermal wells in Tebing Tinggi for geochemical investigations. While these thermal wells have a historical background, they have not yet been comprehensively examined for their potential and geochemical characteristics of the thermal water. Such research would further assist in assessing the geochemical characteristics of thermal water and its source as an input to the subsurface geological conditions of the Tebing Tinggi area. The geochemical data indicate that the thermal water originates from meteoric water, which is categorized as immature water because of its high Mg content. We also found that a major interpreted fault bounds Tebing Tinggi, the Tebing Tinggi Fault, which correlates with fault and fracture density (FFD) modelling. Tebing Tinggi has a high density of fractures in the centre of the town. Additionally, the water is classified as sodium bicarbonate water, formed through interactions among deep-seated hot water, surface water, and the surrounding rocksThe thermal water reservoir in Tebing Tinggi is characterized as a low-enthalpy geothermal system, with estimated temperatures ranging from 58 to 123°C. The reservoir’s circulation depth is projected to range between 1.2 and 2.67 km, with an average of approximately 1.7 km. Both tectonics and volcanic activity play important roles in generating thermal water at Tebing Tinggi

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Published

2026-08-04

Issue

Vol. 41 No. 5 (2026): Forthcoming Issue: No. 81

Section

Geology

License

Copyright (c) 2026 Eri Sarmantua Sitinjak, Danni Gathot Harbowo

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How to Cite

Sitinjak, E. S., & Harbowo, D. G. (2026). Geochemical Investigation of Thermal Water Wells in Tebing Tinggi, North Sumatra, Indonesia: Geology and Preliminary Insights into Their Sources. Rudarsko-geološko-Naftni Zbornik, 41(5), Article in press. https://doi.org/10.17794/rgn.2026.5.8