Determining gas contents of magmas that produce submarine basaltic balloons eruptions: Foerstner 1891 and Socorro 1993
Submarine eruptions that produce basaltic balloons are an uncommon eruption style only observed in five cases during historical times. Two well-studied examples occurred at Foerstner volcano in 1891 (Pantelleria, Italy) and at Socorro island, Mexico in 1993. Magmas erupted during these events were crystal-poor, alkali-rich trachybasalts to basanites. Pre-eruption gas contents (CO 2 and H2O) have been determined using Fournier Transform Infrared Spectroscopy (FTIR) analysis of melt inclusions in olivine and plagioclase phenocrysts. Both eruptions were found to be enriched in carbon dioxide and water relative to other ocean island basaltic compositions. Foerstner inclusions contain 0.17 wt.% to 1.31 wt.% water and 928 ppm to 1834 ppm CO 2. Socorro inclusions contained higher volatile contents ranging from 0.17 wt,% to 1.09 wt.% water and notably higher CO2 values from 318 ppm to 3512 ppm. Both eruptions contain sufficient pre-eruption volatiles to produce highly buoyant clasts at the water depth where venting occurred (250-400 m). Individual volatile trends suggest that open system degassing and concentration of CO2 gas in a foam layer prior to eruption may also have played an important role in generating the excessive vesicularity of the balloon clasts. Calculated balloon rise rates indicate transit times from the seafloor to the surface of up to a few minutes for meter-scale clasts. Positive buoyancy of basaltic balloons in general is likely facilitated by the formation of a quenched crust that isolates large interior gas cavities from cooling and water absorption during ascent through the water column. These results could allow for a clearer understanding in the formation of basaltic balloon eruptions.
"Determining gas contents of magmas that produce submarine basaltic balloons eruptions: Foerstner 1891 and Socorro 1993"
Dissertations and Master's Theses (Campus Access).