Hf isotopic compositions of the standard zircons for U-Pbdating  

作　　者：XUPing WUFuyuan XIELiewen YANGYueheng 

机构地区：[1]InstituteofGeologyandGeophysics,ChineseAcademyofSciences,Beijing100029,China

出　　处：《Chinese Science Bulletin》2004年第15期1642-1648,共7页

摘　　要：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 either in 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 reliable ^176Hf/^177Hf isotopic ratios for zircon in either in 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 obtained ^176Hf/^177Hf ratios are 0.282316±4 (n=34,2σ) for91500, 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, with ^176Lu/^177Hf ratios of -0.00031, 0.000036,0.00083 and 0.00127. Zircons 91500 and CZ3 show narrowervariations in ^176Hf/^177Hf and ^176Lu/^177Hf ratios than those of zircons CN92-1 and TEMORA, and thus are appropriate standards for the Hf isotope analysis.Using the newly published Yb isotopic abun- dances 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 either in 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 reliable 176Hf/177Hf isotopic ratios for zir- con in either in 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 stan- dards in high spatial resolution U-Pb dating, 91500, CZ3, CN92-1 and TEMORA, are measured, respectively. The ob- tained 176Hf/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, with 176Lu/177Hf ratios of ~0.00031, 0.000036, 0.00083 and 0.00127. Zircons 91500 and CZ3 show narrower variations in 176Hf/177Hf and 176Lu/177Hf ratios than those of zircons CN92-1 and TEMORA, and thus are appropriate standards for the Hf isotope analysis.

关 键 词：铪同位素 标准锆石 U-PB定年 LA-MC-ICPMS 等压干扰修正 

分 类 号：P597.2[天文地球—地球化学]