Effects of Hydrogen on Kinetic Processes in Nominally Anhydrous Minerals

California Institute Of Technology, Pasadena CA

Investigators

Abstract

A major reservoir of water within our planet is the water bound in minerals that we would nominally consider to be anhydrous. Such minerals include olivine, garnets and pyroxenes. This water is most commonly bound in the form of hydroxyl (OH) groups. It has an important influence on a wide variety of processes in the geological world, and may be particularly important in the deep earth. This project follows on previous work by a team of researchers that has been studying these minerals for over two decades and is now focusing on an effort to use secondary ion mass spectroscopy (SIMS) in combination with infrared (IR) spectroscopy to quantify hydrogen concentrations in these phases. It is proposed to apply this technique to study processes relevant to hydrogen transport and its effects on kinetic processes in the Earth's mantle. The proposed program will be divided into a calibration effort, the measurement of the diffusion processes of hydrogen in the important upper mantle mineral olivine, and the characterization of minute inclusions of water that result from the gradual loss of bound water from its mineral host. Researchers currently accept that a volume of water equal to or greater than all the water in the oceans of our planet is bound in minerals nominally considered anhydrous. This water is an important reservoir in the terrestrial water cycle, a source of volatiles that drives processes in the mantle, and an agent that impacts physical and chemical properties of the host such as diffusion, radiation stability, color, dielectric constant, and melting. The research proposed here will broaden our understanding of the important roles trace amounts of hydrous components play in the properties of solid materials. It will improve the ability of this laboratory to offer its services to a range of visitors who come to analyze hydrogen using these facilities. Furthermore, the community will benefit from our development of new standards for SIMS analysis of hydrogen in minerals, which will be shared with other labs. Traces of bound water in minerals also occur in a variety of synthetic products of our technological world such as semiconductor supports, optical crystals, fibers, and oscillator crystals. In many of these hosts, the trace components play a major role in determining the properties of the material. Analytical methods used to study minerals have a direct carry-over to the study of synthetic technological products.