| Description |
The laser ablation split stream technique allows for concurrent measurement of Lu-Hf and U-Pb isotopes in zircon by consuming one sample volume, ensuring a direct relationship between crystallization age and Hf-isotope ratios. This is an improvement over common in situ techniques that utilize two sample volumes. In this study, we describe a new method for measuring Lu-Hf and U-Pb isotopes on zircons termed Dual Multicollector Laser Ablation Split Stream ICMPS (DM-LASS -ICPMS). The method is thus far unique because it uses two ThermoFinnigan Neptune Plus multicollector mass spectrometers, which allows high precision measurements of U-Pb as well as Hf. The robust nature of this technique is demonstrated through analyses of 5 natural zircons (91500, Ple š ovice, Mudtank, Temora-2, R33) and 3 synthetic zircons (MUNZirc 1, 3, and 4) with a 53 μ m laser spot. Furthermore, the usefulness of this technique is confirmed by 190 measurements on zircons in rhyolites of the Bruneau-Jarbidge volcanic center. The Bruneau-Jarbidge center, located in the central Snake River Plain of Idaho, is an expression of the Yellowstone hotspot (YHS), and was active from 12.7-8 Ma. The ε Hf values of zircons from the Bruneau-Jarbidge volcanic center range from -15 to -1.5, indicating a period of increased basaltic input and suppression of a crustal signature that is associated with increased melt production. |
