Collaborative Research: Fe-Mg Interdiffusion in Orthopyroxene and Olivine: A Study Using Rutherford Backscattering to Measure Fe-Mg Diffusion Coefficients at 600-900 Degrees C

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Cherniak EAR-0229279 Chemical zoning of minerals in terms of their Fe/(Fe+Mg) value can be used to constrain the rates and nature of a variety of geological processes, if the rate of Fe-Mg interdiffusion is known for the minerals of interest. The goal of this project is to measure Fe-Mg interdiffusion rates for the common minerals orthopyroxene and olivine as a function of temperature and oxygen fugacity. Rutherford backscattering will be used to measure the Fe/(Fe+Mg) profiles produced in laboratory experiments. This will permit very short (200 nm) compositional profiles to be measured. Because of the comparatively slow rate of diffusion in orthopyroxene, previous attempts to measure Fe-Mg interdiffusion coefficients for orthopyroxene have been unsuccessful. Diffusion in olivine will also be studied because of disagreement among published diffusion data sets for olivine and to extend the range of measurements to lower temperatures (600-900 degrees C).