ABSTRACT

Using laser-ablation inductively coupled plasma mass spectrometer (LA-ICPMS), we have improved the reliability of the abundance data for trace-elements in geochemical samples using a glass bead ablation method. The glass beads were made of mixture of 0.1 g sample and 1.0 g of lithium-tetraborate preliminary prepared for an analysis of major components using a X-ray fluorescence (XRF) technique. The present method has several advantages: 1) higher sensitivity than that achieved by the XRF method, 2) obviation of erroneous measurements due to incomplete dissolution of heavy minerals, and 3) simple, rapid and user friendly sample preparation procedures for the analysis of both the major and trace elements. Development of this method constitute: 1) femtosecond laser-ablation for minimal elemental fractionation during the laser ablation, 2) new software to control all the laser, sample stage movement as well as triggering the data acquisition using the ICP-MS, and 3) a newly designed sample cell to enhance the transport efficiency of the sample aerosol into the ICP. Moreover, to improve the data quality for both the major and trace elements, calibration lines were defined based on the Li-normalized signal intensities and the reported abundance values for the analytes in well distributed GSJ geochemical reference samples. These improvements enabled us to analyze whole-rock compositions at ≤100 sec/sample. Using this method, the precisions of analyses were better than 10% for Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Mn, Co, Ga, Rb, Sr, Y, Zr, Nb, La, Pr and Nd; 20% for P, Zn, Sn, Ce, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Th, and U, and 30% for Fe, Cs, Ba, and Eu. For Ni and As, precisions of the measurements was not better than 30%. Reliabilities of analyses were better than 10% for Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Mn, Co, Rb, Sr, Y, Zr, Cs, Ba, La, Ce, Nd, Sm, Gd, Tb, Dy, Yb, Lu, Hf, Th and U; <20% for Zn, Ga, Nb, Sn, Pr, Sm, Eu, Ho, Er, Tm and Ta, and 30% for P. For Fe, Ni and As, reliability of the measurement was not better than 30%.