RII Track-4: Why are Young Volcanic Rocks Undateable: Chemistry, Environment, or Instrumentation?

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Nontechnical Description Geochronology is the field of science that determines the age of earth materials using trace radioisotopes contained in rocks and other minerals when they were formed. Different methods used for radiometric dating apply to different materials and vary in the timescales over which they are accurate. This fellowship enables an early career researcher at the University of Alaska Fairbanks and a graduate student trainee to collaborate with researchers at the Oregon State University. While there they will use state-of-the art equipment to determine the age of young volcanic rocks from Alaska's Aleutian and Wrangell arcs. Precise geological dating of young volcanic rocks is important in understanding the eruptive history of volcanoes in Alaska, volcanic and seismic hazards assessment, and tectonic reconstructions. The project will investigate how the chemistry and environments of the samples and the sensitivity and precision of available measurement instrumentation contribute to the uncertainties in determining the age of young volcanic rocks. The research will enable the development of new methods to accurately date young volcanic rocks and lead to improved research capabilities for the PI at his home institution. The training and collaborations accrued through this project will enrich the careers of the participating faculty and students. Technical Description This award will allow researchers at the University of Alaska-Fairbanks to collaborate with the Oregon State University Argon Geochronology Laboratory (OSU-AGL) to produce high-precision 40Ar/39Ar geochronology data to determine the age of volcanic rocks and products from Alaska?s Aleutian and Wrangell arcs. Accurate dating of these young volcanic rocks is hampered by uncertainties arising from radiochemistry within the samples, limitations on the available instrumentation, and mass fractionation processes in the magma chamber. This project overcomes some of these difficulties through systematic experimentation of the volcanic rocks using the noble gas multi-collector mass spectrometer and software available at the OSU-AGL. The researchers will select samples from a broad range of tectonic-magmatic settings, for example, monogenic cones, intraplate, arc-transform magmatism, and arc magmatism, to investigate potential mass fractionation influences. The PI and his graduate student will extend their expertise with the use of a noble gas mass spectrometer by peak-hopping on a single detector and will be trained in the operation of modern instrumentation with the potential to enhance the research instrumentation and capabilities at their home institution.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.