Gas fluxes and compositions of two active volcanoes in Northern Chile: Lascar and Lastarria

The Central Andes Volcanic Zone of northern Chile comprises a ~1200 km long volcanic district extending from the Atacama region on the northe to the Arica and Parinacota region.Lascar and Lastarria are among the most actively degassing volcanoes of the several (more than 30) potentially active in the region. They both host persistent fumarolic fields and generate sustained plumes above the main craters. Here, we report on simultaneous in-situ and remote volcanic gas measurements aimed at obtaining the very first degassing budget for major volatiles released by these fumarolic fields. Using quick deployable scanning DOAS and SO2 camera systems we obtained time-averaged SO2 fluxes of ~ 500 t d-1 and ~ 970 t d-1 for Lascar and Lastarria, respectively. These data were integrated with plume compositional data, obtained using a portable MultiGAS analyzer and sets of base-treated filter packs, to indirectly calculate fluxes of other volcanic species (H2O, CO2, H2, HCl, HF, HBr and HI) from the fumarolic fields. We estimate H2O and CO2 fluxes of ~ 4400 t d-1 and ~ 470 t d-1 for Lascar and ~ 12200 t d-1 and ~ 1100 t d-1 for Lastarria. These numbers are similar to those charcteristic of other medium-sized active subduction zone volcanoes, and out the basis to better constraining the volatile budget for the Northern Chile arc segment.