DETERMINATION OF MAJOR, TRACE AND RARE-EARTH ELEMENTS IN ROCKS BY DCP-AES

Abstract

Direct current plasma atomic emission spectrometry (DCP—AES) allows rapid and precise determinations of most petrologically and geochemically significant elements in igneous rocks. The method described here uses three different solutions (major elements, trace elements and rare-earth elements) to determine 29 elements. Although there are few interelement or matrix interferences we consistently find differential enhancements of Al, Sr and Ba that are related to Ca contents. We use an empirical correction to remove this effect. Also, there is a direct spectral overlap of Nd onto the Dy line and minor deviations from linearity at low concentrations of Rb and V.

Our test results indicate that the precision (1σ RSD) is 2% or better for 22 elements, better than 5% for 6 elements and ∼ 6% for Rb. The accuracy of the method, judged by comparison of measured to accepted values for well-known U.S.G.S. standards, is sufficient for most types of petrologic and geochemical research.