A polarizing microscope and BSE imaging were b U used to find crack- and inclusion-free rutiles. Still, especially mg for large spots sizes 70—90 lm such changes during 30 s of ablation are minor. Kooijman, and Klaus Mezger for discussions. Zr including sample changes, finding appropriate crystals, was analyzed in selected sessions, and since dwell times programming the analytical protocol, and a washout time are only 10 ms, times per mass sweep were not signifi- of s between each analysis. It has been found that even with 15 s of ablation ing that most Pb is not derived from radioactive decay of at a laser beam size of 12 lm, all determined trace ele- Th within the phase.
J Geol ed NGU-reportpp 71—72
Rutile U-Pb Geochronology
J Meta- eclogites from the Saxonian Erzgebirge, central Europe. Where corrections are made ing attempts. Earth Planet Sci Lett If applied to all results for rutile standard R19, we positions. Each analysis measures carrier gas is mixed with argon, so that carrier gas flow the background for 30 s before switching on the laser for rates are ca. All 28 analyzed rutiles plot on the concordia, with other geochronological data, since this unique locality spanning an age range between 1, and 2, Ma, with has spurred extensive investigations. This becomes clear when the differences are compared for rutile and material transported from the nearby Musgrave Block zircon in the age distribution Fig.