Estimation of Fe3+ from electron microprobe analyses: observations on calcic amphibole and chlorite |
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Authors: | C. E. JACOBSON |
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Affiliation: | Department of Earth Sciences, Iowa State University, Ames, Iowa 50011, USA |
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Abstract: | ABSTRACT Metabasites and metagreywackes from the Pelona and Rand Schists of southern California were analysed using three different electron microprobes. For all three instruments, the estimated Fe3+ contents of calcic amphibole, chlorite and epidote are positively correlated. For some samples, there is an additional correlation between high estimated Fe3+ and the presence of magnetite. These results imply that microprobe analyses can be used to discern relative differences in Fe3+. However, microprobe data and calculations on the sensitivity of the correction procedures to systematic analytical errors indicate that estimated values of Fe3+ are not significant in an absolute sense. Thus, estimates of Fe3+ are meaningful when comparing samples analysed with a single microprobe, but must be used with caution when comparing analyses obtained on more than one probe. |
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Keywords: | Calcic amphibole chlorite electron microprobe ferric iron Pelona Schist Rand Schist |
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