Using the in situ zircon U-Pb dating method of LA-ICPMS, we analyzed the 31 Ma old SHRIMP U-Pb age of the Yongsheng nepheline syenite from southern Jilin Province under different spot sizes. The obtained ages are comp...Using the in situ zircon U-Pb dating method of LA-ICPMS, we analyzed the 31 Ma old SHRIMP U-Pb age of the Yongsheng nepheline syenite from southern Jilin Province under different spot sizes. The obtained ages are comparable with that of SHRIMP in both accuracy and precision. The age is also identical to that of the Yinmawanshan gabbro from the Liaodong Peninsula within error. Both the Yongsheng nepheline syenite and the Yinmawanshan gabbro represent the youngest known exposed intrusions in northeastern and even eastern China. The results indicate the Eocene mantle-derived magmatic underplating, and the rapid crustal uplifting of this region since 30 Ma. The analyses also document extremely high LREE concentrations and relatively flat REE patterns for the zircons from the Yongsheng nepheline syenite, which represent a new type of zircon REE pattern.展开更多
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 mu...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.展开更多
基金co-supported by the National Natural Science Foundation of China(Grant Nos.40133020 and 40272045)the Chinese Ministry of Science and Technology of China(Grant No.G1999043202)the Chinese Academy of Sciences and the Key Laboratory of Continental Dynamics,Northwest University,the Ministry of Education of China.
文摘Using the in situ zircon U-Pb dating method of LA-ICPMS, we analyzed the 31 Ma old SHRIMP U-Pb age of the Yongsheng nepheline syenite from southern Jilin Province under different spot sizes. The obtained ages are comparable with that of SHRIMP in both accuracy and precision. The age is also identical to that of the Yinmawanshan gabbro from the Liaodong Peninsula within error. Both the Yongsheng nepheline syenite and the Yinmawanshan gabbro represent the youngest known exposed intrusions in northeastern and even eastern China. The results indicate the Eocene mantle-derived magmatic underplating, and the rapid crustal uplifting of this region since 30 Ma. The analyses also document extremely high LREE concentrations and relatively flat REE patterns for the zircons from the Yongsheng nepheline syenite, which represent a new type of zircon REE pattern.
文摘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.