In situ simultaneous determination of trace elements, U-Pb and Lu-Hf isotopes in zircon and baddeleyite

摘要

This paper describes a combined method of simultaneously measuring U-Pb and Lu-Hf isotopes as well as trace elements in Phalaborwa baddeleyite and 91500, GJ-1, TEMORA-1 and SK10-2 zircons by means of Neptune MC-ICPMS and Agilent Q-ICPMS connected to a 193 nm excimer laser ablation system. Material ablated by laser was carried in different proportions into Q-ICPMS for U-Pb isotopic and trace elemental and MC-ICPMS for Lu-Hf isotopic compositions. Experiments indicate that different proportions of ablated material for the Q-ICPMS and MC-ICPMS (6:4, 5:5 and 4:6 respectively) do not show any bias for the zircon/baddeleyite U-Pb age, Lu-Hf isotope and trace elemental compositions within analytical errors. Using 40-60 gm spot size, the obtained U-Pb ages of Phalaborwa baddeleyite, 91500, GJ-1, TEMORA and SK10-2 zircons are 2065 +/- 15 (2 sigma, n=20), 1063 +/- 6 (2 sigma, n=19), 613 +/- 6 (2 sigma, n=20), 416 +/- 5 (2 sigma, n=20) and 32.6 +/- 0.5 (2 sigma, n=20) Ma, respectively. The Hf-176/(177) Hf ratios are 0.281231 +/- 24 (2SD, n=20), 0.282310 +/- 35 (2SD, n=19), 0.282028 +/- 34 (2SD, n=20), 0.282687 +/- 34 (2SD, n=20) and 0.282752 +/- 53 (2SD, n=20), respectively. The obtained trace elemental compositions are identical to the reference values. Therefore, this kind of technique makes it possible to simultaneously obtain the U-Pb age, Lu-Hf isotopes and trace elemental compositions of zircon and baddeleyite, which could be an important tool in solving problems in earth sciences.