Abstract
We have developed a method to analyze all rare earth elements in silicate glasses and zircon minerals using a high lateral resolution secondary ion mass spectrometer (NanoSIMS). A 2nA O− primary beam was used to sputter a 7–8-μm diameter crater on the sample surface, and secondary positive ions were extracted for mass analysis using an accelerating voltage of 8 kV. A high mass resolving power of 9,400 at 10% peak height was attained to separate heavy REE from oxide of light REE. A multi-collector system combined with peak-jumping by magnetic field was adjusted to detect REEs and silicon-30 for calibration. Based on results of NIST SRM610 glass, sensitivities of REEs vary from 3 cps/ppm/nA of Lu to 13 cps/ppm/nA of Eu. Reproducibility of REE/Si ratios is better than 18% at 2σ. Secondary ion yields of REEs show positive relationships with their ionization potential of second valence. REEs of AS3, QGNG, and Torihama zircons were measured and calibrated against those of 91500 standard zircon. SIYs of REEs of zircon are identical to those of the glass standard. AS3 and QGNG data are generally consistent with those of previous work. Torihama REE data combined with the whole rock data provide partition coefficients of REEs between silicate melt and zircon. The relationship between these coefficients and ionic radius is explained by an elastic moduli model.
Highlights
Rare earth elements (REEs) are an essential resource in industry (Kato et al, 2011; Hein et al, 2013) because they have unique optical and magnetic properties, and are necessary for high performance magnet and emitting phosphor of LED
We have developed a method to measure all REEs by a high lateral resolution secondary ion mass spectrometer (NanoSIMS) with a multi-ion collector system to reduce data acquisition time
The Secondary Ion Yield (SIY) is calculated by measurements of standard samples with known amounts of REEs
Summary
Rare earth elements (REEs) are an essential resource in industry (Kato et al, 2011; Hein et al, 2013) because they have unique optical and magnetic properties, and are necessary for high performance magnet and emitting phosphor of LED. Among these analytical methods, both ICP-MS coupled with laser-ablation sampling technique (LA-ICP-MS) and SIMS instrument have a potential to detect REEs of sub-ppm level and a lateral spatial resolution of less than 50 μm scale. This method requires a large mass spectrometer with a high magnetic dispersion such as Cameca IMS-1280 and SHRIMP The latter method is more sensitive than the former, while it takes a longer time to measure all REEs and matrix peak by a single ion counting detector with switching the magnetic field at least 17 times (Sano et al, 1999). We discuss the physico-chemical mechanism of secondary ion yields of REEs in this work
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