Acquisition of a multi-collector, inductively coupled plasma mass spectrometer (MC-ICP-MS)

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An Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) will be installed in the Radiogenic Isotope Laboratory at the University of Wisconsin - Madison. The new MC-ICP-MS will replace an existing instrument that was installed in 1999, and will be coupled to a recently installed femtosecond laser ablation system. The new instrumentation will be used for research in three areas of isotope geochemistry: metal stable isotopes, U-series geochronology, and long-lived isotope geochronology and radiogenic tracers. Work in stable metal isotopes will include studies involving Mg, Si, and Fe, with a major effort expended on experimental determination of isotope fractionation factors. In addition, a significant effort will involve in situ isotopic analysis of Archean and Proterozoic banded iron formations, black shales, and carbonates. Research in U-series geochronology will be directed towards understanding the evolution of 100 kyr volcanic systems, where 238U-230Th ages are compared with 40Ar/39Ar ages, as well as extensive geochemical data, including Sr, Nd, Pb, and Hf isotopes. A new initiative on caldera complexes will provide comparisons with earlier work on central vent/composite volcanoes. Work on long-lived geochronological systems and isotope tracers, including U-Th-Pb, Lu-Hf, and Rb-Sr, will include in situ U-Pb/Lu-Hf zircon studies by femtosecond laser ablation, coupled with O and Li isotope studies of the same materials; projects will include Hadean zircons, as well as Cretaceous zircons that are part of a broader timescale initiative. In addition, in situ Sr and Pb isotope analyses of feldspars by femtosecond laser ablation will be pursued, both for provenance studies, as well as volcanic evolution studies; for the former, Sr and Pb analysis will be coupled to single-grain 40Ar/39Ar analysis. The new instrumentation will be used by students and post-docs at UW-Madison, and will also host visiting scientists from the Midwest and other areas.