Collaborative Research: Investigating Magmatic Differentiation in a Fossil Upper-Crustal Silicic Magma System: Stillwater Range, NV

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Volcanic eruptions involving high-silica rhyolite magmas are explosive, violent, and have high hazard potential. Yet, there remain significant debates as to how these magmas are generated and when and why they erupt. Understanding the processes and timescales related to these questions is key to developing effective volcanic hazard programs and requires an understanding of how the physical and thermal conditions of a magmatic system change over timescales ranging from days to millions of years. Efforts focused on monitoring and imaging the subsurface at active volcanoes can provide some of this information, but they cannot inform on processes that occur on very long timescales (thousands to million years). Consequently, research on systems where both erupted and non-erupted portions of the magmatic system are preserved can be used to better understand the entire history of a volcanic system. The goal of this project is to study a ‘fossil’ magmatic system – the IXL pluton (Nevada) –in an effort to constrain the processes that lead to the generation, and possible eruption, of high-silica rhyolite magma. Funding will support two graduate and three undergraduate students from Purdue University, Stanford University, and the University of Nevada-Reno. An additional important outcome of this work will be the production of a student-led documentary that will highlight the research, with an emphasis on women conducting field-based scientific research. This will be done through collaboration with the Science Communication Hitchcock Project within the Reynolds School of Journalism at the University of Nevada-Reno and will result in the dissemination of this research to the general public in an engaging fashion.Most of the proposed mechanisms for production of high-silica rhyolite involve its separation from a crystal-rich magma reservoir through gravitationally driven processes like crystal settling and compaction. Importantly, both processes should produce vertical geochemical and textural gradients in magma reservoirs. The Miocene IXL pluton offers an ideal location to document these gradients because it is well exposed in a coherent crustal section with a known paleo-vertical orientation. To assess whether these gradients are present, the PIs will utilize high-density geochemical measurements coupled with electron back scattered diffraction (EBSD) textural studies and constrain the timescales over which they occurred using high-precision U-Pb zircon geochronology. Additionally, U-Pb zircon geochronology, diffusion chronometry, and geochemical studies will be used to determine whether any of the overlying volcanic rocks are related to the pluton and to assess the magmatic processes that led to their eruption. The combination of these techniques will provide a holistic view of silicic magma evolution in the upper crust and can be used to better interpret the geophysical data that is used to assess volcanic hazards at modern volcanoes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.