First study of the heat and gas budget for Sirung volcano, Indonesia

With at least four eruptions over the last 20Â years, Sirung is currently one of the more active volcanoes in Indonesia. However, due to its remoteness, very little is known about the volcano and its hyperacid crater lake. We report here on the first measurements of gas and heat emissions from the volcano. Notable is the substantial heat loss from the crater lake surface, amounting to 220Â MW. In addition, ~17Â Gg of SO2, representing 0.8% of Indonesian volcanic SO2contribution into the atmosphere, ~11Â Gg of H2S, ~17Â Gg of CO2, and ~550Â Gg of H2O are discharged into the atmosphere from the volcano annually. The volatiles degassed from Sirung magmas are subjected to hydrothermal fluid-rock interactions and sulfide depositions, initiated by the disproportionation of SO2. These processes lead to distinct gas compositions and changing lake water chemistry (in the sub-craters and the main crater lake). However, the occurrence of SO2-rich fluids and strong gas flux appear to highlight a rapid fluid transfer to surface, avoiding re-equilibration with lower temperature rocks/fluids in the conduits