Boudinage: an effective medium to evaluate stress during lava dome growth
Yan Lavallée1 , Jonathan M. Castro2, Anthony Lamur1, Jackie E. Kendrick1, Janine Birnbaum1, Honor James1
Affiliations: 1Earth and Environmental Sciences, Ludwig-Maximilians-Universität, 80333 Munich, Germany 2Institute of Geosciences, Johannes Gutenberg University, Mainz, Germany
Presentation type: Poster
Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 99
Programme No: 3.16.26
Abstract
Obsidian Dome and Glass Creek are lava domes erupted around 1350CE along the Inyo Chain at Long Valley Caldera (California, USA). The lava domes exhibit similar chemistries but contrasting crystallinities, which we interpret to have promoted different rheologies and by extension, emplacement conditions. Both lava domes display frequent dm-scale enclaves which have been variably deformed, stretched and ruptured to form boudins within an obsidian matrix. Some boudins reveal sharp boundaries and fractures associated with brittle behaviour, whereas others show undulating edges with pinch out ends we ascribed to partly ductile behaviour. These rheological textures along with the limited extent of shear during and following boudinage suggests that the boudins formed at high temperature late during dome growth; thus, we suggest that boudinage may be an important marker to assess stress conditions during dome growth. We flank our field observations with thermal analysis to constrain the glass transition temperature and cooling rate, and direct pull-tests to quantify the tensile strength of the enclaves at eruptive temperature. We use the dataset to discuss emplacement conditions of these two lava domes.