IMPROVED EPMA BACKGROUND SELECTION FOR ACCURATE Sr MEASUREMENTS IN PLAGIOCLASE

摘要

Strontium is an important trace element in plagioclase feldspar, both for diffusion chronometry andbecause its partition behaviour is important in understanding crystal-melt evolution (e.g., [1, 2]).Its low concentration makes accurate background characterisation critical in EPMA. This ishampered by an interference with the Si-Kβ satellite line. Whilst the severity of this interferenceis reduced using a PET crystal, there is a contribution from the tail of the interfering peak to thelower background position and depending on the spectral resolution, to the peak itself. Typically,the background is measured by using an upper background position and a flat background isassumed, thereby removing the requirement to measure the lower background position (e.g., [3]).This while providing a reasonable approximation, may not completely remove the interferencecontribution.