Radiogenic geothermal systems of Bangka Island, Indonesia: Implications of high heat production and tectonic framework

The presence of geothermal manifestation in Bangka Island (Southeast Sumatra, Indonesia) with the absence of Quaternary volcanic activity and also relatively low seismicity events has raised intriguing questions on the control of the geothermal system in this area. As the regional tectonic setting of Indonesia volcanic geothermal systems has been known, that of non-volcanic geothermal systems such as radiogenic system become an issue to be investigated. This study reports the geochemistry and petrography analysis of Triassic granite related to radiogenic production at the vicinity of hot springs in Bangka Island. Surface temperatures of the Bangka hot springs range from 37 to 70.7 °C and pH values vary between 5.6 and 7.5. These hot springs are discharging either in close to massive granite bodies or occur in between two major NE-SW striking faults zones, i.e., Pemali fault and Payung fault. Our results indicate the average radiogenic heat production of Late Triassic Klabat granite in the northern area ranges from 28.5 to 38.34 μWm−3 and the southern area ranges from 28.3 to 49.5 μWm−3. In comparison to similar granite belt located in Malaysia, heat production of granitoid in Bangka hot springs is four times higher, possibly due to their different granite origins