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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Last updated: December 19, 2000