Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/30630
The effects of degassing-induced crystallization have been observed in diverse eruption styles and melt compositions. The majority of studies examine how degassing as a whole impacts crystallinity or the rheological characteristics of the degassing melt. In this thesis, I analyze the degassing of volatiles and crystallinity in tholeiitic basalt glasses which originate from various eruption pressure regimes to evaluate the effect of individual volatiles on the induced microlite crystallization. Concentrations of H2O, CO2, S, and Cl in basaltic glassy selvages were analyzed in nine samples collected from subaerial, subglacial, and submarine environments between 169 m and 3980 m water depth, corresponding to 0.01 MPa to 40 MPa eruption pressures, and compared to respective bulk microlite crystallinities. Measured volatile contents were corrected for microlite crystallization to obtain the undegassed value of each volatile in the basalt melt. The corrected values were compared to calculated theoretical undegassed values to calculate the degree of degassing which is 0-28% for H2O, 94 to 100% for CO2, and 0-90% for S in the different samples. Correlations between crystallinity and the degassing of any individual volatile are not present, but relationships between pressure and the degassing of S and H2O are, respectively, exponentially and linearly present. The primary degassing of S occurs at depths shallower than 500 m below sea level. At depths greater than 500 m, the S content in the magma is strongly dependent on melt composition.