MAJOR AND MINOR OXIDE AND TRACE-ELEMENT DETERMINATION IN SILICATE ROCKS BY DIRECT-CURRENT PLASMA OPTICAL-EMISSION ECHELLE SPECTROMETRY

A technique for the determination of major concentrations of SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O, minor levels of TiO2, P2O5, and MnO, and trace concentrations of Ba, Cr, Cu, Ni, Sr, V, and Zn, in semi-microsamples (200 mg) of powdered whole rock, is described. Chemically diverse standard reference rocks are used both for calibration and assessment of accuracy. A lithium metaborate fusion melt of each standard or sample is dissolved in dilute HNO3 containing Cs+ at a level of 0.2% (w/v). The resulting solution is used to perform all analyses except those for Na2O and K2O, which are determined in a portion of the original sample solution wherein the Cs+ concentration has been raised to 0.32% (w/v). Analyses of both portions of each sample solution are performed using an optical emission spectrometer/spectrograph equipped with an echelle monochromator and a dc argon plasma excitation source. Trace element detection limits ranged from 2 ppm for Cu to 15 ppm for Zn. A study of precision based on replicate determinations in three splits of the proposed USGS reference basalt BHVO-1 yielded the following results: (1) For analyses of the major and minor oxide constituents, values of the percent relative standard deviation (RSD) ranged from 1 for CaO, to 21 for P2O5. (2) For trace element determinations, values of the RSD ranged from 2 for Cu, to 19 for Zn. © 1979, American Chemical Society. All rights reserved.