A New K-feldspar Liquid Hygrometer

A New K-feldspar Liquid Hygrometer: Initial Experiments, Calibration, and Applications

Presenter: Magdalen Grismer

Presenter Status: Undergraduate student

Department: Geology

Screenshot URL: https://drive.google.com/uc?id=18RKj3GjFG2LSb05bN3Ws2PxI328tYoRn

Abstract:
Large-scale silicic eruptions are the most devastating on earth. The volcanic properties that create massive formations such as Bishop Tuff in California, and the Snake River Plain by Yellowstone, Wyoming are a function of temperature, pressure, melt composition, and volatiles. To better understand future eruptions, it is essential to have quantitative values of these factors, a liquid hygrometer (based on the plagioclase liquid hygrometer of Waters & Lange, 2015) is a model to determine pre-eruptive water content or temperature. One of the unique mineral properties of alkali feldspar is its sensitivity to temperature changes, and it is prevalent in volcanics. A phonolite and trachyte sample were examined to provide whole rock composition data. Phase equilibrium experiments were run on the phonolite to determine formation pressure and temperature to aid in calibration of the new hygrometer. Applied to additional data the model has an r2 value of 0.89, with a standard deviation of 0.37.