Flux-Free Fusion of Silicate Rock Preceding Acid Digestion for ICP-MS Bulk Analysis

摘要

We present a new method for the decomposition of silicate rocks by flux-free fusion in preparation for whole-rock trace element determination (Sc, Rb, Sr, Y, Zr, Nb, Cs, Ba, rare earth elements and Hf) that is especially applicable to zircon-bearing felsic rocks. The method was verified by analyses of RMs of mafic (JB-1a, JB-2, JGb-1) and felsic rocks (JG-3, JR-3, JSd-1, GSP-2, G-2). Pellets of powdered sample (up to 500 mg) without flux were weighed and placed in a clean platinum crucible. The samples were then fused in a Siliconit- tube furnace and quenched to room temperature. The optimum condition for the fusion of granitic rock was determined to be heating for 2–3 min at 1600 C. The fused glass in the platinum crucible after heating was decomposed using HF and HClO4 in a Teflon- beaker. Decomposed and diluted sample solutions were analysed using a quadrupole inductively coupled plasma-mass spectrometer. Replicate analyses (n = 4 or 5) of the RMs revealed that analytical uncertainties were generally < 3% for all elements except Zr and Hf (- 6%) in JG-3. These higher uncertainties may be attributed to sample heterogeneity. Our analytical results for the RMs agreed well with recommended concentrations and recently published concentrations, indicating complete decomposition of our rock samples during fusion.