DataSheet1_NanoSIMS Analysis of Rare Earth Elements in Silicate Glass and Zircon: Implications for Partition Coefficients.PDF

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.

本研究开发了一种利用高横向分辨率二次离子质谱仪（NanoSIMS）分析硅酸盐玻璃与锆石矿物中全部稀土元素（rare earth elements，REE）的方法。实验采用2纳安的氧负离子原束在样品表面溅射出直径7至8微米的蚀坑，并以8千伏的加速电压引出二次正离子进行质谱分析。本方法在峰高10%处实现了9400的高质量分辨率，可将重稀土元素与轻稀土元素的氧化物有效分离。通过调试多接收器系统并结合磁场峰跳法，实现对稀土元素与硅-30的检测以完成校准。基于美国国家标准与技术研究院（National Institute of Standards and Technology，NIST）SRM610玻璃标准物质的测试结果，稀土元素的灵敏度范围为镥（Lu）的3 cps/ppm/nA至铕（Eu）的13 cps/ppm/nA。稀土元素与硅的比值的重现性在2倍标准偏差下优于18%。稀土元素的二次离子产额（Secondary Ion Yields，SIYs）与其第二价态电离电势呈正相关关系。本研究对AS3、QGNG与Torihama锆石中的稀土元素进行了检测，并以91500锆石标准物质作为校准参考。锆石中稀土元素的二次离子产额（SIYs）与玻璃标准物质的二次离子产额一致。AS3与QGNG的测试数据与已有研究成果总体一致。结合全岩测试数据与Torihama锆石的稀土元素数据，可获得硅酸盐熔体与锆石之间的稀土元素分配系数。上述分配系数与离子半径之间的关联可通过弹性模量模型进行阐释。