The past year has been a time of transition as I worked to complete several research projects begun at Brown University while initiating new research directions at BGSU.

Research completed at Brown included a major study on the effect of sheet silicates (micas) on the distribution of aqueous fluids and diffusional transport properties in polycrystalline framework silicate aggregates (quartz and feldspars). The results of this work demonstrate that the presence of micas greatly influences the diffusional transport properties of silicate aggregates; apparently, aqueous fluids form a thin (1-3 monolayers thick) interconnected film along sheet silicate/framework silicate interfaces providing a rapid path for diffusional transport. The fluid film does not, however, have the bulk properties of water and can support a differential shear. Other studies included determining the kinetics of oxygen grain boundary diffusion in natural and hot-pressed calcite aggregates over a range of temperature and coexisting fluid compositions. Also, silicon grain boundary diffusion rates have been experimentally determined in polycrystalline quartz aggregates under both anhydrous and hydrothermal conditions. When combined with previously determined oxygen grain boundary diffusion and oxygen and silicon volume diffusion rates, these new data can be used to predict the strength of quartz aggregates and to evaluate the important role of diffusion-accommodated mechanisms in the deformation of quartz aggregates.

Research efforts at BGSU have been dominated by construction and calibration of a high temperature and pressure laboratory. The facility consists of equipment for conducting experiments at controlled temperatures and pressures, to 800¡C at up to 400 MPa confining pressure and to 1500¡C at one atmosphere, under controlled chemical environments. The first series of experiments utilizing this new facility were done in the spring of 1997, and comprised a University Honors thesis project for E. Jewel. The project involved an experimental determination of the kinetics of grain growth of quartz (SiO2), an important geological and industrial silicate phase. This research was done in collaboration with two other members of the Center for Materials Science, Dr. Samajdar in Technology Systems and Dr. Heckman in the Center for Microscopy and Microanalysis. The results of this study can be used to predict the rate of grain growth in quartz aggregates as a function of temperature and fluid composition, and provide valuable insights into the mechanisms of diffusional transport across versus along grain boundaries in silicate aggregates.