The production of small volume silicic rocks in areas of oceanic crust is understood with less certainty than the production of silicic rocks in a continental setting. While the anatexis of silicic continental crust produces rhyolites within a continent, it is unlikely to occur in Iceland, an island composed of basaltic oceanic crust. After analyzing rhyolitic samples I collected from multiple ...

1 The diversity of microbial communities inhabiting two terrestrial volcanic glasses of 2 contrasting mineralogy and age was characterised. Basaltic glass from a <0.8 Ma 3 hyaloclastite deposit (Valafell) harbored a more diverse Bacteria community than the 4 younger rhyolitic glass from ~150-300AD (Dόmadalshraun lava flow). Actinobacteria 5 dominated 16S rRNA gene clone libraries from both site...

We report the first systematic study of H2O speciation in dacitic melt with total dissolved H2O ranging from 1.4 to 2.6 wt%. Samples were heated in a one-atmosphere tube furnace at 480–590 °C for certain durations and then quenched in water or air. Species concentrations were measured with Fourier transform infrared (FTIR) spectroscopy. At a given temperature, the equilibrium constant for the r...

Wellsch Valley tephra, near Swift Current, southwestern Saskatchewan, and Galt Island Medicine Hat, southeastern Alberta, have been referenced in the literature since 1970s, but little is available on their physical chemical attributes – necessary information if they are to be recognized elsewhere. This study seeks remedy this situation. Both a calc-alkaline rhyolitic composition with hornblend...

H O diffusion plays a major role in bubble growth and volcanic eruption. We report a comprehensive study of H O 2 2 diffusion in rhyolitic melts and glasses. This new study and previous investigations together cover a wide range of Ž . conditions: 400–12008C, 0.1–810 MPa, and 0.1–7.7 wt.% total H O content H O . In order to constrain how the 2 2 t diffusivity depends on H O , both the diffusion...

[1] The transfer of volatiles from the Earth’s interior to the atmosphere occurs through degassing of magma, the dynamics of which assert a significant control on volcanic eruptions. The first and most critical step in degassing is the nucleation of gas bubbles, which requires that a sufficient number of volatile molecules cluster together to overcome the free energy associated with the formati...

The diffusion of water in a peralkaline and a peraluminous rhyolitic melt was investigated at temperatures of 714–1,493 K and pressures of 100 and 500 MPa. At temperatures below 923 K dehydration experiments were performed on glasses containing about 2 wt% H2Ot in cold seal pressure vessels. At high temperatures diffusion couples of water-poor (\0.5 wt% H2Ot) and water-rich (*2 wt% H2Ot) melts ...