Elevated gas flux and trace metal degassing from the 2014-2015 fissure eruption at the Baroarbunga volcanic system, Iceland

The 2014 Baroarbunga rifting event in Iceland resulted in a 6-month long eruption at Holuhraun. This eruption was characterized by high lava discharge rate and significant gas emission. The SO2 flux for the first 3 months was measured with satellite sensors and the petrologic method. High-resolution time series of the satellite data give 1200kg/s that concurs with 1050kg/s obtained from melt inclusion minus degassed lava sulfur contents scaled to the mass of magma produced. A high-purity gas sample, with elevated S/Cl due to limited chlorine degassing, reveals a similar degassing pattern of trace metals as observed at Klauea (Hawai'i) and Erta Ale (Ethiopia). This suggests a common degassing mechanism at mantle plume-related volcanoes. The trace metal fluxes, calculated from trace element to sulfur ratios in the gas sample and scaled to the sulfur dioxide flux, are 1-2 orders of magnitude stronger at Holuhraun than Klauea and Erta Ale. In contrast, volcanoes at convergent margins (Etna and Stromboli, Italy) have 1-2 orders of magnitude higher trace element fluxes, most likely caused by abundant chlorine degassing. This emphasizes the importance of metal degassing as chlorine species. Short-lived disequilibria between radon daughters, Pb-210-Bi-210-Po-210 measured in the gas, suggest degassing of a continuously replenished magma batch beneath the eruption site. Earlier and deep degassing phase of carbon dioxide and polonium is inferred from low (Po-210/Pb-210) in the gas, consistent with magma transfer rate of 0.75m/s.