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

Abstract

The 2014 Bárðarbunga 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 1200 kg/s that concurs with 1050 kg/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 Kīlauea (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 Kīlauea 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, 210Pb‐210Bi‐210Po 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 (210Po/210Pb) in the gas, consistent with magma transfer rate of 0.75 m/s.

A New Degassing Model to Infer Magma Dynamics from Radioactive Disequilibria in Volcanic Plumes

“…The new measurements presented in this paper have benefited from recent methodological and analytical improvements [21], and they are in fair agreement with previously published data ( [19], and references therein). Based on the concept of the previous dynamic degassing model [15], a new theoretical framework for the degassing of radionuclides is presented here.…”

“…The emanation coefficient of lead in basaltic systems appears to be higher in calk-alkaline systems than in other geodynamical settings [21]. At Mount Etna, like at other arc-related basaltic volcanoes, it has a value of approximately 1.0 ± 0.5% [14,17,31,32].…”

“…Alpha counts provide a direct measure of 210 Po activity while beta counts correspond to the detection of 210 Bi beta decay particles. Beta emissions of 210 Pb cannot be directly measured because of their energies that are too low, so that 210 Pb is measured via 210 Bi one month after sampling when both isotopes have reached radioactive equilibrium [21]. Radionuclide activities on filter samples were determined by subtracting the detector background (electronic noise and some unblocked cosmic rays) and by taking into account the detector efficiency and an attenuation factor for alpha particles [25].…”

“…Bi (5.01 days half-life) thoroughly decays away in about one month, filter samples were taken back to Laboratoire Magmas et Volcans in Clermont-Ferrand within a few days after collection. Untreated filters were analysed with a low-background noise alpha-beta counting unit (IN20 Canberra) following the procedure described in Gauthier et al [21]. Repeated measurements were carried on over a month after collection in the field, each analytical cycle lasting 48 h (one cycle comprises eight 6-hour-long counting blocks that are ultimately averaged, the mean activity being considered as the "instantaneous" activity at the time t i + 24 h, where t i is the starting date and time of a given cycle).…”

Shifting DOC concentration and quality in the freshwater lakes of the Kangerlussuaq region: An experimental assessment of possible mechanisms

“…Perhaps increased marine primary production in the Arctic since 2003 has enhanced sulfate deposition to lakes via oxidation of dimethyl sulfide (DMS; Arrigo, van Dijken, and Pabi 2008). Additionally, more frequent volcanic eruptions, such as that of the Icelandic volcano Bárðarbunga that released massive clouds of sulfur dioxide in 2014, could be responsible for the delivery of sulfate to lakes in the Kangerlussuaq region (Gauthier et al 2016). Shifts in terrestrial C inputs may also play a role in reduced DOC.…”