Subsurface density architecture and structural controls of the Dendang non-volcanic geothermal area, west Bangka, Indonesia

Nur Ramadhani; Korhan Cengiz

doi:10.58524/jograv.v1i2.183

Authors

Nur Ramadhani Department of Physics, Institut Teknologi Sumatera Author
Korhan Cengiz College of Information Technology University of Fujairah Author https://orcid.org/0000-0001-6594-8861

DOI:

https://doi.org/10.58524/jograv.v1i2.183

Keywords:

Satellite gravity, Subsurface density structure, Non-volcanic geothermal, Gravity inversion, Dendang

Abstract

The Dendang hot-spring area in West Bangka, Indonesia, represents a non-volcanic geothermal setting developed within a granitic geological environment. This study investigates the subsurface density architecture beneath the Dendang geothermal area using satellite-derived gravity data. Free-Air Anomaly and elevation data obtained from the TOPEX data portal were processed to construct the Complete Bouguer Anomaly, followed by spectral analysis, regional–residual anomaly separation, two-dimensional forward modelling, and three-dimensional gravity inversion. The Complete Bouguer Anomaly ranges from approximately 21.0 to 42.7 mGal, indicating substantial lateral variation in subsurface density. The gravity models reveal contrasting shallow low-density and deeper high-density domains. Based on comparison with the regional geological framework, the higher-density bodies are interpreted as being compatible with granitic and basement-related rocks, whereas lower-density zones are associated with shallower sedimentary and less consolidated materials. The three-dimensional model indicates that high-density domains remain significant to the maximum investigated depth of approximately 8.3 km, although their lithological identity is non-unique and should be interpreted cautiously. The spatial relationship between gravity gradients, mapped geological structures, and the Dendang hot-spring manifestation suggests that structural discontinuities may influence subsurface fluid circulation. The observed surface manifestation, with a temperature of approximately 49 °C, should be regarded as a discharge characteristic rather than a direct indicator of reservoir temperature.

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