Isotopic analyses were performed by using a Micromass IsoProbe multicollector inductively coupled plasma mass spectrometer (MC-ICPMS) with a laser-ablation system. Laser-beam diameter was 35 micron, yielding ablation pits ~15 micron deep. All measurements were made in static mode, using Faraday detectors for 238U, 232Th, and 208-206Pb and an ion-counting channel for 204Pb. Ion yields were 0.5 mV/ppm.