NSF Award
2434212
The composition of potassium feldspar, a common in continental magmatic rocks, can record the intensive conditions it experiences as it is growing from a melt. The research team will calibrate a water-dependent geothermometer based on sanidine compositions. The calibration will be applicable to determine the conditions of crystallization of some of the world's most-important and best-studied suites, including voluminous (>1000 cubic kilometers) ignimbrites and batholithic plutons. Six undergraduates from Sonoma State, a Hispanic-serving institution, will participate in the project, including 3 from a program that promotes STEM fields to under-represented groups. Three students from a high-school internship program will participate. Three undergraduates from Davis, a Hispanic-serving institution, will also participate. <br/><br/>This project will generate new phase equilibria results, a hygrometer applicable to sanidine- and anorthoclase-bearing magmas, and a new method for estimating the equilibration temperatures and H2O contents of plutonic rocks. Silicic magmas represent the final products of planetary differentiation and can erupt in enormous volumes. Voluminous silicic eruptions require that short- or long-lived volumes of mush (crystals + melt) must exist in the crust. However, there is ongoing debate about the origins and lifespans of such systems, with conflicting views from numerical models, isotopic and trace element data, and the plutonic and volcanic records. The intensive variables recorded by potassium feldspar have been underutilized in this debate, largely due to a lack of appropriate models. This project will involve experimental calibration of a new K-feldspar hygrometer/thermometer that will constrain the conditions (i.e., temperature, pressure, H2O content) of formation, storage, and extraction of a broad range of silicic magmas. Six undergraduates from Sonoma State, a Hispanic-serving institution, will participate in the project, including 3 from a program that promotes STEM fields to under-represented groups. Three students from a high-school internship program will participate. Three undergraduates from Davis, a Hispanic-serving institution, will also participate.<br/><br/>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.
