Geochemical analysis in a new Light: Applications of the laser Raman Microprobe

Jill Dill Pasteris, Ph.D.
Washington University, St. Louis, Missouri

Wednesday, March 3, 1999
3:00 p.m.—Pacific Forum

Geochemists, petrologists, economic geologists, and other earth scientists in many instances require chemical-structural analyses of solids, liquids, and gases. Raman spectroscopy can provide molecular-structural, species-specific analyses of all three states of matter. The laser Raman microprobe moreover enables non-destructive, in situ analyses of entities as small as a few cubic micrometers in volume within a matter of minutes. The species-specific nature of the analyses permits the interpretation of such important parameters as oxygen fugacity (e.g., distinguishing carbon monoxide from carbon dioxide in gas mixtures), pH (e.g., distinguishing sulfate from bisulfate in aqueous solutions), and pressure (e.g., distinguishing among such polymorphs as calcite and aragonite). The Raman spectrum provides a sensitive measure of the chemical environment of an entity, for instance distinguishing between carbon dioxide in the free gas phase and the same species dissolved in water. Raman microprobe analysis can be applied to geological materials as diverse as fluid inclusions in minerals, to minerals in human tissue, to rock surfaces on Mars or undersea.

This talk will address the fundamentals of Raman spectroscopy and will summarize several different geological applications of the technique.

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