Ascent and emplacement dynamics of obsidian lavas inferred from microlite textures

Dynamics of obsidian £ows inferred from microstructures: insights from microlite preferred orientations

The flow of obsidian lava leads to crystal alignments that reflect both the accumulated strain and the type of flow across the surface. Microlite preferred orientations are used to investigate the emplacement dynamics, strain history, and structural evolution of Obsidian Dome, eastern California. Measurements of three-dimensional microlite trend and plunge in samples from the near-vent region, ...

Constraints on rheology of obsidian lavas based on mesoscopic folds

The geometry of mesoscopic single and multiple layer folds in rhyolitic obsidian ̄ows is investigated. Folds are composed of obsidian embedded in a matrix of pumice. Folds form by buckling processes as indicated by discontinuous deformation between obsidian and pumice layers and by the geometries of wavetrains. Buckling occurs through a continuum of styles controlled largely by the thickness ra...

Vesiculation rates of obsidian domes inferred from H2O concentration profiles

[1] Explosivity of rhyolite domes depends on bubble nucleation and growth. To understand these processes, we measure millimeter-scale variations in H2O by synchrotron Fourier transform infrared (FTIR) spectromicroscopy on interlayered obsidian-pumice samples. The H2O contents of all samples are above the 1-atm solubility value ( 0.10wt.%) and decrease systematically towards vesicular zones, ind...

Eruption dynamics inferred from microlite crystallization experiments: Application to Plinian and dome-forming eruptions of Mt Pelée (Martinique, Lesser Antilles)

Decompression experiments have been conducted to simulate syn-eruptive crystallization in the volcanic conduit, in order to infer magma ascent rates and conditions during domeforming and Plinian eruptions of silicic arc volcanoes. The experiments were carried out starting from Mt Pelée rhyolitic interstitial melt (76 wt. % SiO2) and consisted in three consecutive steps: hydration, decompression...

Rapid ascent and emplacement of basaltic lava during the 2005–06 eruption of the East Pacific Rise at ca. 9°51′N as inferred from CO2 contents