Effect of Hydrogen on the Electrical Conductivity of Olivine

97-06105 Wanamaker 在地幔矿物中发现的显著的氢浓度和在橄榄石中实验测量的快速氢扩散率导致一些研究人员认为，在地球上地幔测量的相对较高的电导率是由橄榄石结构中的氢缺陷造成的。 然而，PI在一个大气压下对电导率的新测量表明，“湿”橄榄石晶体最初的导电性低于“干”晶体，并且观察到“湿”晶体的电导率随时间增加，在800 ° C下约10小时后接近干晶体的电导率。 这种电导率的增加伴随着晶体中氢含量的降低，如使用红外光谱法测定的。 在该提案中，PI提出了实验来确定在高压和氢逸度下有氢和无氢的橄榄石的相对电导率，并定量地确定氢对橄榄石中缺陷的浓度和迁移率以及输运的影响。 上地幔的性质。这些实验将确定氢缺陷的性质，它们在橄榄石晶体结构中的迁移率，它们对其他橄榄石缺陷的浓度和迁移率的影响，以及这些参数如何随温度和压力而变化。 这些数据将允许预测氢对橄榄石的其他运输和流变性能的影响，并测试现有的理论模型的高电导率异常和低地震速度异常的地幔来源。 ***

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. ***