Gravity-based structural characterization of a radiogenic geothermal system in a non-volcanic setting: A case study from Pelawan, West Bangka, Indonesia

Meita Tasya Setiawan; Mikael Syväjärvi

doi:10.58524/jograv.v1i1.108

Authors

Meita Tasya Setiawan Physical Sciences, Wahana Krida Konsulindo Author
Mikael Syväjärvi Alminica AB, Ulrika, Östergötlands Län Author

DOI:

https://doi.org/10.58524/jograv.v1i1.108

Keywords:

Non-volcanic geothermal system, Subsurface structural interpretation, Structural control, Gravity modeling, Granite-hosted

Abstract

Radiogenic geothermal systems represent a type of non-volcanic geothermal resource generated by the decay of radioactive elements within crystalline basement rocks, particularly granites. Despite Indonesia’s well-known volcanic geothermal potential, radiogenic geothermal systems remain poorly investigated. This study presents a preliminary assessment of subsurface structures associated with the radiogenic geothermal signature in the Pelawan area, West Bangka Regency, using gravity data analysis. Secondary gravity and topographic datasets derived from the TOPEX satellite were processed to obtain Complete Bouguer Anomaly (CBA) values. Two-dimensional (2D) and three-dimensional (3D) gravity modeling were subsequently conducted to characterize subsurface density contrasts and identify structural features controlling geothermal manifestations. The gravity method is particularly suitable for distinguishing subsurface lithological variations based on density contrasts between anomalous bodies and surrounding formations. The modeling results reveal the presence of multiple fault structures surrounding the Pelawan geothermal manifestation, suggesting structural control of the geothermal system. The subsurface stratigraphy is interpreted to consist of Pleistocene alluvium (1.8–1.9 g/cm³), Triassic Tanjung Genting Formation (2.1 g/cm³), Triassic–Jurassic Klabat Granite (2.55 g/cm³), and the Pemali Formation as basement rock (2.6 g/cm³). The deeper sections of the model are dominated by granitic formations, which are interpreted as the primary radiogenic heat source. The identified fault structures are likely associated with granite intrusions and may act as pathways for geothermal fluid circulation. These findings provide new insights into the structural and lithological controls of radiogenic geothermal systems in non-volcanic settings in Indonesia and highlight the potential of the Pelawan area for further geothermal exploration.

References

1. Hosono, T., Hartmann, J., Louvat, P., Amann, T., Washington, K. E., West, A. J., Okamura, K., Böttcher, M. E., & Gaillardet, J. (2018). Earthquake-induced structural deformations enhance long-term solute fluxes from active volcanic systems. Scientific Reports, 8(1), 1–12. https://doi.org/10.1038/s41598-018-32735-1

2. Zhang, Z., Yao, H., Wang, W., & Liu, C. (2021). 3-D crustal azimuthal anisotropy reveals multi-stage deformation processes of the Sichuan Basin and its adjacent regions. Journal of Geophysical Research: Solid Earth, 127, e2021JB023289, 1–17. https://doi.org/10.1029/2021JB023289

3. Liu, S., Suardi, I., Xu, X., Yang, S., & Tong, P. (2021). The geometry of the subducted slab beneath Sumatra revealed by regional and teleseismic traveltime tomography. Journal of Geophysical Research: Solid Earth, 126(1), 1–29. https://doi.org/10.1029/2020JB020169

4. Dewi, K. C. S., Siregar, R. N., Ningati, T. I., Pulungan, Z. N., Indriyawati, A., & Takahashi, H. (2025). Analysis of subsurface faults using 3D gravity method based on satellite image data: Insights into Indo-Australian and Eurasian plate subduction in the formation of an accretionary prism. International Journal of Hydrological and Environmental for Sustainability, 4(3), 135–148.

5. Hariyono, E., & S, L. (2018). The characteristics of volcanic eruption in Indonesia. In Volcanoes – Geological and Geophysical Setting, Theoretical Aspects and Numerical Modeling, Applications to Industry and Their Impact on Human Health. https://doi.org/10.5772/intechopen.71449

6. McCaffrey, R. (2009). The tectonic framework of the Sumatran subduction zone. Annual Review of Earth and Planetary Sciences, 37, 345–366. https://doi.org/10.1146/annurev.earth.031208.100212

7. Hristov, V., Stoyanov, N., Valtchev, S., Kolev, S., & Benderev, A. (2019). Utilization of low enthalpy geothermal energy in Bulgaria. IOP Conference Series: Earth and Environmental Science, 249(1). https://doi.org/10.1088/1755-1315/249/1/012035

8. Taruna, R. M., & Banyunegoro, V. H. (2018). Earthquake relocation using double difference method for 2D modelling of subducting slab and back arc thrust in West Nusa Tenggara. Jurnal Penelitian Fisika dan Aplikasinya (JPFA), 8(2), 132–143. https://doi.org/10.26740/jpfa.v8n2.p132-143

9. Collings, R., Lange, D., Rietbrock, A., Tilmann, F., Natawidjaja, D., Suwargadi, B., Miller, M., & Saul, J. (2012). Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography. Journal of Geophysical Research, 117, 1–23. https://doi.org/10.1029/2011JB008469

10. Jihad, A., Muksin, U., Syamsidik, & Ramli, M. (2021). Earthquake relocation to understand the megathrust segments along the Sumatran subduction zone. IOP Conference Series: Earth and Environmental Science, 630, 012002. https://doi.org/10.1088/1755-1315/630/1/012002

11. Xu, J., & Kono, Y. (2002). Geometry of slab, intraslab stress field and its tectonic implication in the Nankai Trough, Japan. Earth, Planets and Space, 54(7), 733–742. https://doi.org/10.1186/BF03351726

12. Kusuhara, F., Kazahaya, K., Morikawa, N., Yasuhara, M., Tanaka, H., Takahashi, M., & Tosaki, Y. (2020). Original composition and formation process of slab-derived deep brine from Kashio Mineral Spring in central Japan. Earth, Planets and Space, 72(1). https://doi.org/10.1186/s40623-020-01225-y

13. Malod, J. A., Karta, K., Beslier, M. O., & Zen, M. T. (1995). From normal to oblique subduction: Tectonic relationships between Java and Sumatra. Journal of Southeast Asian Earth Sciences, 12(1–2), 85–93. https://doi.org/10.1016/0743-9547(95)00023-2

14. Li, C. F. (2011). An integrated geodynamic model of the Nankai subduction zone and neighboring regions from geophysical inversion and modeling. Journal of Geodynamics, 51(1), 64–80. https://doi.org/10.1016/j.jog.2010.08.003

15. Stern, R. J. (2002). Subduction zones. Reviews of Geophysics, 40(4), 3-1–3-38. https://doi.org/10.1029/2001RG000108

16. Utama, H. W., Mulyasari, R., & Said, Y. M. (2021). Geothermal potential on Sumatra Fault System for sustainable geotourism in West Sumatra. JGE (Jurnal Geofisika Eksplorasi), 7(2), 126–137. https://doi.org/10.23960/jge.v7i2.128

17. Tabei, T., Hashimoto, M., Miyazaki, S., Hirahara, K., Kimata, F., Matsushima, T., Tanaka, T., Eguchi, Y., Takaya, T., Hoso, Y., Ohya, F., & Kato, T. (2002). Subsurface structure and faulting of the Median Tectonic Line, southwest Japan inferred from GPS velocity field. Earth, Planets and Space, 54(11), 1065–1070. https://doi.org/10.1186/BF03353303

18. Tongkul, F. (2017). Active tectonics in Sabah – seismicity and active faults. Bulletin of the Geological Society of Malaysia, 64, 27–36. https://doi.org/10.7186/bgsm64201703

19. Maryanto, S. (2017). Geo techno park potential at Arjuno–Welirang volcano hosted geothermal area, East Java, Indonesia (multi geophysical approach). AIP Conference Proceedings, 1908. https://doi.org/10.1063/1.5012712

20. Sujitapan, C., Kendall, J. M., Chambers, J. E., & Yordkayhun, S. (2024). Landslide assessment through integrated geoelectrical and seismic methods: A case study in Thungsong site, southern Thailand. Heliyon, 10(2), e24660. https://doi.org/10.1016/j.heliyon.2024.e24660

21. Chambers, J., Holmes, J., Whiteley, J., Boyd, J., Meldrum, P., Wilkinson, P., Kuras, O., Swift, R., Harrison, H., Glendinning, S., Stirling, R., Huntley, D., Slater, N., & Donohue, S. (2022). Long-term geoelectrical monitoring of landslides in natural and engineered slopes. The Leading Edge, 41(11), 768–776. https://doi.org/10.1190/tle41110768.1

22. Whiteley, J. S., Watlet, A., Uhlemann, S., Wilkinson, P., Boyd, J. P., Jordan, C., Kendall, J. M., & Chambers, J. E. (2021). Rapid characterisation of landslide heterogeneity using unsupervised classification of electrical resistivity and seismic refraction surveys. Engineering Geology, 290, 106189. https://doi.org/10.1016/j.enggeo.2021.106189

23. Martinho, E. (2023). Electrical resistivity and induced polarization methods for environmental investigations: An overview. Water, Air, & Soil Pollution, 234. https://doi.org/10.1007/s11270-023-06214-x

24. Kusumayudha, S. B., Lestari, P., & Paripurno, E. T. (2018). Eruption characteristic of the sleeping volcano Sinabung, North Sumatera, Indonesia, and SMS gateway for disaster early warning system. Indonesian Journal of Geography, 50(1), 70–77. https://doi.org/10.22146/ijg.17574

25. Meju, M. A., & Le, L. (2002). Geoelectromagnetic exploration for natural resources: Models, case studies and challenges. Surveys in Geophysics, 23, 133–205.

26. Lange, D., Tilmann, F., Henstock, T., Rietbrock, A., Natawidjaja, D., & Kopp, H. (2018). Structure of the central Sumatran subduction zone revealed by local earthquake travel-time tomography using an amphibious network. Solid Earth, 9(4), 1035–1049. https://doi.org/10.5194/se-9-1035-2018

27. Lin, J. Y., Sibuet, J. C., Hsu, S. K., & Wu, W. N. (2014). Could a Sumatra-like megathrust earthquake occur in the South Ryukyu subduction zone? Earth, Planets and Space, 66(1), 1–8. https://doi.org/10.1186/1880-5981-66-49

28. Siringoringo, L. P., Sapiie, B., Rudyawan, A., & Sucipta, I. G. B. E. (2024). Origin of high heat flow in the back-arc basins of Sumatra: An opportunity for geothermal energy development. Energy Geoscience, 5(3), 100289. https://doi.org/10.1016/j.engeos.2024.100289

29. Hochstein, M. P., & Sudarman, S. (1993). Geothermal resources of Sumatra. Geothermics, 22(3), 181–200. https://doi.org/10.1016/0375-6505(93)90042-L