EAR-PF: Diffusion of water in clinopyroxene

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Dr. Elizabeth Ferriss has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the Lamont-Doherty Earth Institute, Columbia University. This study will investigate the diffusion of water in the clinopyroxene mineral group, with particular emphasis on the effects of aluminum, titanium, and iron. The larger goal of the project is to develop a new tool to determine the ascent rate of magma near the surface of the Earth. Accurately quantifying this rate is important because physical models suggest that the ascent rate largely controls the vigor of volcanic eruptions. Two sets of experiments will be conducted. First, a set of natural clinopyroxenes will be dehydrated, and their diffusion profiles will be measured. This approach allows the investigation of a wide range of natural systems and creates an important link with previous experiments that were conducted in a similar way. Second, aluminum- and water-rich clinopyroxene will be synthesized and equilibrated with a melt at high pressure. This system will then be decompressed, resulting in dehydration of both the melt and the pyroxenes. This experiment will require a substantial amount of preparation, but the increase in difficulty is offset by the value of closely simulating the natural processes experienced by crystals as they grow, incorporate water, and dehydrate upon decompression.This study will test a novel analytical technique for measuring a parameter that is central to physical models of volcanic eruptions and will also provide data that will be highly useful for investigating the mantle's water budget, which is important at the planetary to tectonic scale. In addition, Dr. Ferriss will co-organize both a geodynamics speaker series and a graduate seminar on diffusion in geological systems.