Major and trace analysis of basaltic glasses by laser-ablation ICP-MS

Abstract

Chemical analysis by laser-ablation ICP-MS can determine a large number of trace elements with a precision approaching traditional whole-rock analysis, but on a scale approaching that achieved by the electron microprobe. These characteristics make it a particularly attractive method for the analysis of volcanic glasses, but at present little is known about systematic errors, especially those from matrix effects. Here we investigate the precision and accuracy of LA-ICP-MS analysis of basaltic glasses for 60 elements, including rare earth elements (REE), large ion lithophile elements (LILE), high field strength elements (HFSE), the first row transition elements (FRTE), as well as less commonly analyzed elements such as Li, Be, Ge, Ga, W, Mo, As, Sb, Sn, Se, Ag, Tl, Bi, Cd and In. The rate of signal decline during ablation was found to vary systematically with the electronic structure of the element, in both calibration material (NIST SRM 612) and unknowns (natural basaltic glass VG-2 and vitrified basalt BCR-2G). These observations allow optimal analytical conditions with the available instrumentation and standards to be established. Analyses of VG-2 and seven of the MPI-DING vitrified rocks, commonly used as secondary standards, obtained under these conditions, are presented.