CAREER: Accessory Minerals as Monitors of the Oxidation State of Magmas and Fluids and Enhancing Scientific Literacy Through Active Education

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In almost all cases, we cannot directly measure key variables that control the properties of magmas and fluids inside the Earth. They are not directly accessible due to their depth of formation, or because these magmas have long since solidified, leaving behind minerals. Thus, the chemistry of the resulting minerals need to be used as proxies, to determine the physical and chemical characteristics of these magmas and fluids. One key variable that remains poorly explored in the accessory group of minerals (e.g., zircon, monazite, and apatite) is the oxygen "pressure" of the magma or fluid from which they crystallized. The goal of this research is to calibrate and understand how the chemistry of these minerals changes in response to changes in the oxygen pressures. These calibrations will take place in a laboratory setting enabling the synthesis of minerals under precision-controlled conditions. Such experiments will serve as stepping stones to explore the formation environment of natural minerals. The accessory minerals zircon, monazite, and apatite are specifically targeted because they are excellent recorders of absolute time. This is so because they structurally accommodate radioactive elements such as uranium and thorium. Thus, changes in the oxygen pressure of a magma can, for example, be explored as a function of time. Oxygen pressure is an important variable in Earth studies because it influences mineral saturation and stability (including economically important minerals) and the viscosity of magmas. Because of this, quantifying the oxygen pressure of past systems, including ancient volcanic systems, will lead to new knowledge to that may help explain why volcanoes erupt. Second, the types of volatiles present during an eruption depends on oxygen pressure, and meaning that magmatic outgassing throughout Earth history has partially influenced the composition of our atmosphere. Third, this research will explore the stability of these minerals in the presence oxidized fluids. Monazite, for instance, is a major host of light rare earth elements, thorium, and uranium in the crust. Understanding the stability and solubility of this mineral will also help researchers explore the mobility of these key heat producing and economically important elements (rare earth elements are found in almost all modern electronics manufactured today). And finally, minerals (zircons) older than 4 billion years represent a key target for application because rocks from this time period are either sparse or altogether absent. This work will therefore result in new knowledge about the environments and conditions that may have prevailed on the earliest Earth. Oxygen fugacity buffered experiments will be conducted in piston cylinder devices at the University of Rochester. In many cases, experimental products will be analyzed by a Laser Ablation Inductively Couple Plasma Mass Spectrometer (LA-ICP-MS; also at the University of Rochester) by the PI, graduate, and undergraduate students. This will provide key training for undergraduates and graduate students in techniques involved in mineral synthesis and mass spectrometry, with applications that extend well beyond the geology/mineralogy field. (LA)-IPC-MS instruments have been used in medical research, biology, chemistry, and materials science, so students will come away with a useful skill set applicable across the STEM fields. In addition, students will receive training in X-ray Absorption Near Edge Structure (XANES) techniques; this work will be undertaken at the Advanced Photon Source, Argonne National Laboratory. The practical training will result in a broad skill set, highly applicable to many areas within and outside the geosciences. The broader impacts of this project come from several activities that implement active learning. This award will enable a partnership with NSF-Funded Noyce program awarded to the Warner School of Education at the University of Rochester. The PI will work with selected K-12 math and science teacher fellows in high-need urban districts in upstate New York - current graduate rates are below 50% - to increase science literacy, to create a better understanding of the different manners in which people learn, to expose teachers to new and evolving methods of teaching, and to create learning experiences that are more interesting, meaningful, and effective for their students. And finally, the PI will design a new course to explore teaching strategies that have been demonstrated to be effective when compared to a traditional lecture. The course will also be built around a research problem identified in this proposal.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.