Development of a Technique for Quantitative Hydrogen Analyses of Geological Materials Using SIMS

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9975549HervigThis award supports the development of a technique for the quantitative microanalysis of hydrogen in geological materials using secondary ion mass spectrometry (SIMS) and ion implantation. Hydrogen influences many geological processes, including melting temperatures of rocks, bubble nucleation leading to volcanic eruptions, and the strength of minerals. Hydrogen is an essential structural constituent of hydrous minerals, and their hydroxyl contents may provide an indicator of volatile activities. The presence of hydrogen in nominally anhydrous minerals represents an important part of the hydrogen budget in the earth's mantle. The proposed research is needed because quantitative microanalyses for H in geological materials cannot now be made without obtaining a standard very close in chemical composition to the unknown. It is not feasible to synthesize standards for every composition of interest and there is no straightforward alternative because no theory exists to predict the calibration based on other standards. Combining this work with the high sensitivity and spatial resolution provided by SIMS will allow us to analyze a wide range of geological phases in standard polished thin sections which we can use to attack many areas of research, including volcanology, metamorphic petrology, low-temperature geochemistry, and high pressure geochemistry. Because the result of this technique development will easily cross from one SIMS to another (of the same manufacturer), the results of our work will also allow researchers at other laboratories to obtain quantitative hydrogen analyses on phases of interest. Ion implantation is a reliable, quantitative method that has been applied to problems in semiconductor analysis for nearly two decades; this technology is readily transferred to geologic materials.***