97-06105 Wanamaker The significant hydrogen concentrations found in mantle minerals and the rapid hydrogen diffusivities measured experimentally in olivine have led several researchers to argue that the relatively high electrical conductivities measured for Earth's upper mantle result from hydrogen defects in the olivine structure. However, new measurements by the PI of the electrical conductivity at one atmosphere show that "wet" olivine crystals are initially less conductive than "dry" crystals and that the conductivity of the "wet" crystals is observed to increase with time, approaching that of the dry crystals after approximately 10 hours at 800=B0C. This increase in conductivity is accompanied by a decrease in the hydrogen content of the crystals as determined using infra-red spectroscopy. In this proposal the PI proposes experiments to establish the relative electrical conductivities of olivine with and without hydrogen at elevated pressure and hydrogen fugacity, and to determine quantitatively the effect of hydrogen on the concentrations and mobilities of defects in olivine and the transport properties of the upper mantle. These experiments will establish the nature of the hydrogen defects, their mobility in the olivine crystal structure, their effect on the concentrations and mobilities of other olivine defects, and how these parameters vary with temperature and pressure. These data will allow predictions to be made about the effects of hydrogen on other transport and rheological properties of olivine and test existing theoretical models of the sources of high electrical conductivity anomalies and low seismic velocity anomalies in Earth's mantle. ***
