Ancient recycled lower crust in the mantle source of recent Italian magmatism

Isotopic analysis of sub-nanogram neodymium loads using new ATONA™ amplifiers

RATIONALE

Emerging research in the geological and nuclear forensics fields demands increasing analytical precision of isotope ratio measurements with decreasing sample sizes. Here we demonstrate the capability of a newly developed amplification technology to make precise neodymium (Nd) isotopic measurements on 100-pg standard loads.

METHODS

The reference materials were analyzed as NdO⁺ to increase the ionization efficiency of the small analyte loads. The Nd isotopic measurements were made using an IsotopX Isoprobe-T thermal ionization mass spectrometer upgraded with the ATONA™ amplifier system. The ATONA™ amplifier system uses capacitance-based amplification as opposed to traditional impedance-based amplification.

RESULTS

The long-term gains of the ATONA™ amplifiers are shown to have less than 1 ppm variability. Repeat measurements of the JNdi-1 reference material demonstrate the ability of the ATONA™ amplification technology to make measurements of ¹⁴³ Nd/¹⁴⁴ Nd ratios with 23 ppm external reproducibility on 100-pg loads. The effect of increasing integration time on analytical reproducibility is also displayed as increasing integration time from 10 to 30 s reduced the external measurement uncertainty from 37 to 23 ppm.

CONCLUSIONS

These measurements represent an improvement of more than a factor of 3 in external measurement reproducibility relative to previously published ¹⁴³ Nd/¹⁴⁴ Nd measurements of 100-pg loads. This new technology will allow for the measurement of smaller samples for precise isotope ratios and open new avenues of research in the geological and nuclear forensic communities.