Structural controls and radiogenic heat sources of a granite-hosted geothermal system in Belitung Island, Southeast Asia tin granite belt

Rabin Fatmansyah; Rofiqul Umam

doi:10.58524/jograv.v1i1.106

Authors

Rabin Fatmansyah Department of Physics, Institut Teknologi Sumatera Author
Rofiqul Umam Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba Author https://orcid.org/0000-0002-7095-5967

DOI:

https://doi.org/10.58524/jograv.v1i1.106

Keywords:

Radiogenic geothermal system, Gravity inversion, Crustal heat production, Granite intrusion, Tin granite belt

Abstract

Belitung Island forms part of the Southeast Asia Tin Granite Belt, a metallogenic province characterized by extensive granitic intrusions enriched in heat-producing elements such as thorium (Th), uranium (U), and potassium (K). The radiogenic decay of these elements generates long-lived crustal heat, providing favorable conditions for the development of non-volcanic geothermal systems. In the Bulding area of Belitung Island, surface manifestations of radiogenic hot springs suggest the presence of subsurface heat sources associated with granitic bodies. However, the geometry, depth extent, and structural controls of these potential heat sources remain poorly constrained. This study applies satellite-derived gravity data and integrated two-dimensional (2D) forward modeling and three-dimensional (3D) inversion to characterize the subsurface structure beneath Belitung Island. Free-air anomaly (FAA), elevation, and coordinate data obtained from the TOPEX dataset were processed to generate a Complete Bouguer Anomaly (CBA) map, revealing anomaly values ranging from −1.541 mGal to 55.846 mGal. The modeling results indicate the presence of high-density intrusive bodies interpreted as granite extending from depths of approximately 16.5 km to near-surface levels (~0.66 km). These bodies are inferred to represent the primary radiogenic heat source responsible for the observed geothermal manifestations. The results provide new geophysical constraints on granite-related non-volcanic geothermal systems in the Southeast Asia Tin Granite Belt and highlight the potential of gravity-based structural modeling for reducing exploration uncertainty in radiogenic geothermal provinces.

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