CHIME monazite dating: Pb analysis on an R_R = 100 mm spectrometer and correction of interferences between Th, U, and Pb with natural monazite

Abstract

This paper outlines an advanced procedure involving the chemical Th–U–total Pb isochron method (CHIME) dating of monazite using a field–emission electron probe microanalyzer (FE–EPMA) equipped with spectrometers of 100 mm Rowland circle (R_R) radius. The higher count rate of R_R = 100 mm wavelength dispersive spectrometer (WDS) compared to R_R = 140 mm WDS enables measurements to be taken in a shorter time. CHIME dating using R_R = 100 mm WDS had previously been difficult because of lower resolution compared to that of R_R = 140 mm WDS. This problem has been overcome by a new interference correction method using natural monazites.