Source strength assessment of volcanic trace elements emitted from the Indonesian arc

We have for the first time estimated volcanic emission of volatile metals for a large regional volcanic source showing permanent activity, namely the Indonesian Arc. We have done this by normalizing concentrations of metals ratios in volcanic plumes to SO2 emission rates. Metal/SO2 ratios measured in magmatic gases are used to estimate emissions from eruptive activity, whereas those measured in fumarolic gases are used to estimate emissions from non-eruptive activity. The SO2 emission rate obtained is 3.5 × 106 tons per year, which represents about 20% of the annual worldwide volcanic flux of SO2. The obtained trace metal (210Po, Pb, Bi, Cd, Zn and Cu) fluxes account for only about 5 to 30% of their global volcanic flux. These relatively low values for trace metal emissions (relative to the volcanic activity and the number of active volcanoes of the region) appear to reflect the andesitic magma composition of the volcanoes of the arc.