This open-file report describes the analytical protocol for measurement of lead (Pb) isotope compositions using the Nu Plasma HR multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) facility in Building 20, Denver Federal Center, Denver, Colo. The facility is supported by The Mineral Resources Program, Geologic Discipline. Data quality is assessed by multiple analyses of the National Institute of Standards and Technology (NIST) lead standard SRM 981, which is routinely run as part of an analytical session and can be compared with the values obtained by double and triple spike thermal ionization mass spectrometry (TIMS). The data for SRM 981 reported here covers the period between April 2004 and May 2005, so analytical variability over a period of a year can be judged.
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