Abstract
Gas transport in silicic magma is a mechanism controlling the degassing rate of magma and hence the explosivity and style of volcanic eruptions. The gas flow through fractures formed in sheared magma is thought to induce efficient degassing from silicic magma; however, the quantitative condition at which magma fractures remains poorly understood. In this study, we observed the formation of brittle fractures and the degassing through the fractures at high temperature and pressure. At a temperature of 850°C, vesicular rhyolite was fractured as well as rhyolitic melt without bubbles at a strain rate of 10-2 s-1. The fracturing induced the localization of deformation, and the degassing and compaction repeatedly occurred. The experimental result indicates that shear fracturing of silicic magma causes efficient degassing in a volcanic conduit.
