Analytical procedure of neon measurements on GV 5400 noble gas mass spectrometer and its evaluation by quartz standard CREU-1

Abstract

Terrestrial in situ-produced stable cosmogenic isotope 21Ne can provide us lots of important geomorphologic information, while the prerequisite for the application of cosmogenic 21Ne in the surface process studies is the accurate measurements of three neon isotopes in the rock samples. To employ cosmogenic 21Ne in solving geological problems, we established a new analytical procedure of neon measurements on the GV 5400 noble gas mass spectrometer. Isobaric interferences on three neon isotopes have been quantified, and among them the correction for the major interference from 40Ar2+ on 20Ne+ was studied in more detail. Instead of the first-order correlation of 40Ar+/40Ar2+ ratio with the H2 partial pressure in the ion source section of the mass spectrometer reported by Professor Niedermann and co-workers in 1993, an excellent power function correlation of the 40Ar2+ counting to that of 40Ar+ has been established in our analytical system for determining the unresolved 40Ar2+ contribution by monitoring the 40Ar+ signal during sample analysis. The calibration experiment using air standard was performed, and then several aliquots of quartz standard CREU-1 were measured to assess the performance of our neon measurements. The average measured cosmogenic 21Ne concentration of CREU-1 (347±7.7×106atomg−1) is consistent with the published value (348±10×106atomg−1), which demonstrates the good analytical accuracy (0.3%) and high measurement precision (2.2%) of our neon measurements. And the MSWD value of 0.49 indicates the good agreement of the apparent dispersion of three aliquots data with their individual measurement errors. The establishment of this analytical procedure for neon measurement provides us a promising way for developing the cosmogenic 21Ne method in many fields of Earth sciences and beyond.