Titanium Isotope Analysis of Igneous Reference Materials using a Double‐spike MC‐ICP‐MS Method

Abstract

Abstract Ti separation was achieved by ion‐exchange chromatography using Bio‐Rad AG 1‐X8 anion‐exchange and DGA resins. For high‐Fe/Ti and high‐Mg/Ti igneous samples, a three‐column procedure was required, whereas a two‐column procedure was used for low‐Fe/Ti and low‐Mg/Ti igneous samples. The Ti isotopes were analysed by MC‐ICP‐MS, and instrumental mass bias was corrected using a 47 Ti‐ 49 Ti double‐spike technique. The 47 Ti‐ 49 Ti double‐spike and SRM 3162a were calibrated using SRM 979‐Cr, certificated value 53 Cr/ 52 Cr true = 0.11339. Isobaric interference was evaluated by analysing Alfa‐Ti doped with Na, Mg, Ca, and Mo, and results indicate that high concentrations of Na and Mg have no significant effect on Ti isotope analyses; however, Ca and Mo interferences lead to erroneous δ 49/47 Ti values when Ca/Ti and Mo/Ti ratios exceed 0.01 and 0.1, respectively. Titanium isotopic compositions were determined for 12 igneous reference materials, BCR‐2, BHVO‐2, GBW07105, AGV‐1, AGV‐2, W‐2, GBW07123, GBW07126, GBW07127, GBW07101, JP‐1, and DTS‐2b. Samples yield δ 49/47 Ti (‰) of −0.035 ± 0.022, −0.038 ± 0.031, 0.031 ± 0.022, 0.059 ± 0.038, 0.044 ± 0.037, 0.000 ± 0.015, 0.154 ± 0.044, −0.044 ± 0.018, 0.010 ± 0.022, 0.064 ± 0.043, 0.169 ± 0.034, and −0.047 ± 0.025 (relative to OL‐Ti, ±2SD), respectively; of which isotopic compositions of DTS‐2b, JP‐1, GBW07101, GBW07105, GBW07123, GBW07126, and GBW07127 are reported for the first time. Standard Alfa‐Ti was analysed repeatedly over a ten‐month period, indicating a reproducibility of ±0.047 (2SD) for δ 49/47 Ti, similar to the precisions obtained for geochemical reference materials.