Guillaume Girard*, John Stix

Dept. of Earth and Planetary Sciences, McGill University, 3450 University St., Montreal QC H3A 2A7, Canada

Abstract

In order to understand possible future scenarios of intracaldera volcanism at Yellowstone, we provide new insights on the generation and eruption of the youngest intracaldera rhyolitic magmas using quartz petrography, geochemistry, and geobarometry. We propose that magma ascent occurred rapidly from the source regions at 8–10 km to the surface along major regional faults, without storage at shallower depths. These source regions coincide with the upper parts of the present-day imaged magma chamber, while the faults focus much of the present-day caldera unrest. Based on these combined observations, we propose that volcanism has a higher probability to resume in three fault-controlled NNW-trending lineaments, the first coinciding with the western caldera rim, the second lying across the central region of the caldera, and the third extending across the northeastern caldera. The first two lineaments focused recent intracaldera volcanism (174–70 ka), while the latter is the most active in terms of current caldera unrest. Future volcanism could include large-volume lava flows and phreato-magmatic rhyolitic eruptions. The identification of these three regions together with potentially rapid eruptive mechanisms may help to better define future monitoring efforts necessary to improve eruption forecasting in this vast area of volcanic unrest.

*Now at Dept. of Geosciences, University of Iowa, Iowa City, Iowa 52242-1379, USA;
Email:

Manuscript received 12 Nov. 2011; accepted 16 May 2012.

DOI: 10.1130/GSATG143A.1