Pb isotope analyses of silicate rocks and minerals with Faraday detectors using enhanced-sensitivity laser ablation-multiple collector-inductively coupled plasma mass spectrometry

208 Pb.Because of the low concentration of Pb in natural silicate rocks and minerals (typically sub parts per million to tens of parts per million), one or more ion counters (ICs, for Hg isotopes and the minor 204 Pb isotope) and Faraday cup (FC) detectors (for the major 206-208 Pb isotopes) have typically been used for analyses of isotope ratios (Kent, 2008a;Kent et al., 2008;Paul et al., 2005).When using ICs, careful adjustment and monitoring of the gain is necessary to obtain accurate results (Kent, 2008a;Paul et al., 2005).In contrast to ICs, FCs are suitable for stable and accurate isotope ratio measurements (Kent, 2008b; Kent et al., 2008;Paul et al., 2005).However, the low sensitivities and low signal-to-noise ratios in FCs limit the application of FC detectors, particularly with 204 Pb.