Abstract

We present in this study the groundwork necessary for the utilization of scanning Auger microscopy (sam) as a high-resolution microprobe for geologic materials. The attributes of sam that allow it to be a useful microanalytic tool for rocks are discussed and demonstrated. The technique is suitable for semiquantitative probing of < 1-μm grains in rocks as well as performing surface studies with very high lateral resolution.

sam analyses of feldspar surfaces suggest that the depth of Auger analysis is sufficient to measure representative bulk chemistries from relatively clean surfaces of crystalline silicates. It is shown that very light sputtering, used to eliminate thin contaminant surface layers due to air exposure and/or solvent residues, should not affect semiquantitative chemical analysis. It is also shown that elements as light as Li can be detected in minerals with sam. Sample charging and degradation can be reduced and/or eliminated by using a beam voltage of 3 keV and currents in the low nanoampere range impinging on tilted specimens that are relatively clean. To demonstrate the technique, we describe an example of performing a semiquantitative chemical analysis of a < 1-μm grain in a rock with chemical lateral resolution slightly better than 1 μm.

sam is also briefly compared with other microanalysis techniques commonly used today, namely epma, sem/eds, and stem/eds. In comparison, the major disadvantage of sam is sample charging and the fact that it is sensitive to electron-beam-stimulated surface degradation. The major advantage of sam over these techniques is a combination of high lateral and depth analytic resolution and ease of light-element detection.

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