Accurate determination of ¹⁴³Nd/¹⁴⁴Nd ratios using TIMS from terrestrial rocks without REE separation

Abstract

We report a new method for determination of ¹⁴³Nd/¹⁴⁴Nd ratio of terrestrial rocks using TIMS. The method allows analysis of samples without inter-REE separation and does not need isobaric correction for ¹⁴⁴Sm. ¹⁴⁵Nd and ¹⁴⁶Nd do not have any stable isobars and show a constant ratio in terrestrial rocks. We use the ratio of these two naturally occurring Nd isotopes to correct instrumental mass fractionation on ¹⁴³Nd/¹⁴⁶Nd ratio. We also use the known ratio of 0.7219 for ¹⁴⁶Nd/¹⁴⁴Nd, which is constant in terrestrial rocks, to convert the corrected ¹⁴³Nd/¹⁴⁶Nd to ¹⁴³Nd/¹⁴⁴Nd in analysed samples. This method allows isotopic analysis without time consuming and expensive REE separation procedures, while producing isotopic data with external precision and accuracy equivalent to standard methods.