EAPSI: Understanding Crystal Cluster Origins in Magmas Erupted from Toba Caldera, Earth's Youngest Supervolcano

Barbee Olivia A, Flagstaff AZ

Investigators

Abstract

Supereruptions, the most violent volcanic eruptions on Earth, are fed by magma reservoirs that contain incredibly large volumes of silica-rich magma. Crystals formed within these magmas and found in their eruptive products contain important information on the processes that lead to such devastating eruptions. This project will investigate the storage conditions and dynamics of the silicic magma reservoir that explosively erupted the voluminous Youngest Toba Tuff (YTT) 74,000 years ago and then quiescently extruded several small rhyolite lava domes at Toba Caldera (Sumatra, Indonesia). These Toba magmas contain unusual quartz crystal clusters that likely record important evidence for the development of their host magma. Quartz clusters have seldom been recognized or studied in silicic volcanic rocks from other caldera-forming magma systems, and thus the Toba quartz clusters will be examined to understand their origin and the implications they have for silicic magma evolution and eruption potential. This research will be conducted at Nanyang Technological University in Singapore under the guidance of Dr. Caroline Bouvet de Maisonneuve, an expert on the use of crystal-scale data to determine magma storage conditions and eruption dynamics. Petrography and cathodoluminescence imaging reveal that quartz clustering is an important process affecting 40-60% of YTT and lava dome crystals. Crystallographic orientations of individual quartz ?units? within clusters will be acquired to identify potential mechanisms for cluster formation, as well as the type of environment from which they originated. Trace element analysis will be used to chemically fingerprint each unit in a given cluster to determine whether the individual units formed under similar magma conditions, and thus potentially at the same time. Results will provide important constraints on the petrological and rheological evolution and dynamics of the Toba magma reservoir and are expected to highlight a transition from pre- to post-caldera magma storage conditions and eruption potential. Toba quartz cluster features will also be compared to those reported from solidified subsurface magma bodies to provide insight on the connection between volcanic rocks and their plutonic counterparts. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Singapore.