** Please join us for coffee and cookies in the GeoCorner Undergraduate lounge (bldg. 320, rm 114) before the talk, at 11:30am! - Seminar will be in room 220~
From crystal-scale to kilometers: what do crystal records tell us about magma reservoir processes?
Crystals in volcanic rocks record processes occurring in magma reservoirs prior to eruptions. Information derived from studying these volcanic crystals, such as crystal ages, mineral thermometry, and time scales of crystal residence derived from intracrystalline diffusion, have greatly improved our understanding of the dynamics of magmas during sub-surface storage. However, these crystal records are necessarily capturing information primarily from crystals’ local environments, and extrapolating from this small (micrometer to centimeter) spatial scale to the spatial scale of magma bodies (hundreds of meters to tens of kilometers) requires placing the information contained in crystals within the context of a conceptual model for how magma reservoirs operate. As with all models, these are simplifications of complex realities that attempt to capture important features of the behavior of the system. However, as these models are often presented as end-member scenarios, different data sets may appear to support different end-members, creating a controversy in the scientific community. As an example, I will use the case of the recent controversy in the literature between “cold” (crystal-dominated) or “warm” (liquid-dominated) storage in sub-volcanic magma reservoirs, which have been presented in some recent literature as incompatible. However, the data used to support each model are not inconsistent once analytical uncertainties are considered. Incorporating a more complex, time-varying model of a magma reservoir removes the apparent conflict, allowing us to address more interesting questions such as “Where, when, and for how long are crystals and/or magmas stored at high temperatures, and how does that relate to magma mobility?”
Kari M. Cooper is a professor in the Department of Earth and Planetary Sciences at the University of California, Davis. Her research is aimed at understanding how magmas evolve and interact with each other and with their surroundings, with a particular focus on dating volcanic crystals to understand the time scales and conditions of magma storage and mobilization prior to eruptions. Dr. Cooper received a B.A. in geology from Carleton College, an M.S. in geology from the University of Washington, and a Ph.D. in geochemistry from University of California, Los Angeles. Prior to her current position at UC Davis, she held appointments as a Geologist at the USGS-Menlo Park, a Postdoctoral Scholar at the California Institute of Technology, and as an Assistant Professor at the University of Washington. Dr. Cooper served on the NAS Committee Committee on Improving Understanding of Volcanic Eruptions (the ERUPT report) and is currently a disciplinary leader in petrology/geochemistry for the Community Network for Volcanic Eruption Response (CONVERSE) Research Coordination Network. She is a fellow of the Geological Society of America and the American Association for the Advancement of Science.