A simple method for precise determination of 23 trace elements in granitic rocks by ICP-MS after lithium tetraborate fusion

An improved alkali fusion method followed by HF-HNO3-HClO4 treatment is performed for simultaneous determination of 23 trace elements (Sr, Y, Zr, Nb, Ba, Hf, Ta, Th, U, and REE) by ICP-MS in rock reference materials: basaltic rocks (JB-2, JB-3) and granitic rocks (JG-1a, JG-2, JG-3). Our improved method offers several advantages including: (1) suppression of whitish precipitates probably composed of insoluble fluorides by addition of HClO4, (2) simple and reliable preparation procedure, (3) instrument calibration which enables straightforward simultaneous multi-elemental analysis, and (4) the very low background levels by using pure lithium tetraborate flux. We obtained the analytical results with a reproducibility of mostly < 2% (1 sigma) for the basaltic rocks and < 7% for the granitic rocks. The higher relative standard deviation (RSD) values for granitic rocks may be attributed to sample heterogeneity of coarse-grained granitic rocks. The analytical results of the granitic rocks demonstrate that Zr and Hf abundances are consistent with the compiled values and that REE concentrations agree well with recently published data, suggesting that the Li2B4O7 fusion method applied in the present study is suitable for the analysis of the granitic rocks.