Date of Award
1989
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Secondary ion mass spectrometry (SIMS) with specimen isolation conditions (an extreme form of energy filtering) is useful in geochemical studies. The presence of molecular ion interferences in SIMS spectra is greatly reduced when analyzing high energy secondary ions (i.e. specimen isolation conditions), thus simplifying the interpretation of mass spectra.;High energy secondary ions were found to be less susceptible to the dramatic changes in ionization yield resulting from the effect of the matrix in secondary ion production. Correlation of ion intensities for glass and crystalline materials of identical composition is possible for most elements when using some form of energy filtering, and thus the use of glass standards for SIMS analysis of minerals is possible. Some matrix effects are still present in the high energy ion population. However, in a given concentration range with a reliable set of standards, quantitative analysis down to the ppm level is available with specimen isolation or conventional energy filtering methods. This has been demonstrated for the rare-earth elements at both trace and major element concentration levels in various mineral grains.;The ionization probability of high energy ions was studied as a function of kinetic energy, first ionization potential, and oxide bond strength. A simple mechanism for the production of high energy secondary ions could not be obtained from these results.;Besides the elimination of molecular ion interferences, the method of specimen isolation is an excellent technique for the analysis of non-conducting samples. Leached, or altered zones up to several hundreds of angstroms in thickness have been observed in SIMS depth profiles of naturally and laboratory dissolved plagioclase. Dissolution of plagioclase in relatively simple laboratory experiments (pH 3.5 and 5.7) forms altered zones depleted of sodium, calcium and aluminum, and enriched (residually) in silicon. For specimens undergoing a more complex set of reactions (dissolution in nature), layers enriched in aluminum were observed in the SIMS profiles. Each of these layers are believed to form during the dissolution process. Qualitatively similar results were obtained using X-ray photoelectron spectroscopy, while SEM analysis has shown the sample surfaces to be "clean" and free of secondary precipitates.
Recommended Citation
Muir, Ian Joseph, "Secondary Ion Mass Spectrometry And Its Application To Studies In Geochemistry" (1989). Digitized Theses. 1792.
https://ir.lib.uwo.ca/digitizedtheses/1792