A new method for MC-ICPMS measurement of titanium isotopic composition: Identification of correlated isotope anomalies in meteorites

Abstract

A new protocol is presented for precise measurements of titanium isotopes in natural samples. Titanium was separated via ion-exchange and extraction chromatography in two stages. Tests on Ti standard solutions show that isobaric interferences from Ca, V, and Cr can be adequately corrected, as long as these elements are present at atomic ratios of Ca/Ti < 20, V/Ti < 2, and Cr/Ti < 0.1. Furthermore, Zr²⁺ and Mo²⁺ have no influences on Ti⁺ signals when atomic ratios of Zr/Ti < 0.002 and Mo/Ti < 0.04. Compared with these correction limits, the purified solutions have corresponding ratios several orders of magnitude lower, indicating that the chemical separation technique is effective. This newly developed method has been successfully applied to geostandards and a wide variety of bulk meteorites. Our results are in good agreement with the data from Trinquier et al. (Science, 2009, 324, 374–376)¹ and reveal a linear correlation between isotope anomalies of two Ti nuclides in bulk meteorites. The correlation reflects incomplete mixing of the carrier phases for Ti isotope anomalies before bulk meteorite formation.