Hf isotopic compositions of the standard zircons for U-Pb dating

Using the newly published Yb isotopic abundances and the mass bias relationship between Yb and Hf, we carried out an analysis of Hf isotopes in the standard zircon 91500 by means of 193 nm laser attached to Neptune multi-collector ICP-MS (LA-MC-ICPMS). The obtained Hf isotopic data, in eitherin situ or line scan modes, are not only identical for different spot sizes, but also are consistent with previously published results obtained on TIMS or other MC-ICPMS machines within errors. This indicates that it is possible to obtain reliable¹⁷⁶Hf/¹⁷⁷Hf isotopic ratios for zircon in eitherin situ or line scan conditions on LA-MC-ICPMS machine, and the applied procedures in our study for elemental interfering correction are appropriate for the purpose of acquiring satisfactory accuracy for Hf isotope analyses. The Hf isotopic compositions of four zircon standards in high spatial resolution U-Pb dating, 91500, CZ3, CN92-1 and TEMORA, are measured, respectively. The obtained¹⁷⁶Hf/¹⁷⁷Hf ratios are 0.282316±4 (n = 34, 2σ) for 91500, 0.281704±6 (n = 16, 2σ) for CZ3, 0.282200±6 (n = 20, 2σ) for CN92-1 and 0.282684±14 (n = 24, 2σ) for TEMORA, respectively, with¹⁷⁶Lu/¹⁷⁷Hf ratios of ~0.00031, 0.000036, 0.00083 and 0.00127. Zircons 91500 and CZ3 show narrower variations in¹⁷⁶Hf/¹⁷⁷Hf and¹⁷⁶Lu/¹⁷⁷Hf ratios than those of zircons CN92-1 and TEMORA, and thus are appropriate standards for the Hf isotope analysis.