ID-TIMS U-Pb geochronology at the 0.1parts per thousand level using 1013 Ω resistors and simultaneous U and 18O/16O isotope ratio determination for accurate UO2 interference correction

We document recent advances in analytical protocols that employ 10(13) Omega resistors in the Faraday cup amplifier feedback loop for high-precision U-Pb geochronology by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). We present a direct comparison of high-precision U-Pb data obtained using different detector systems, including dynamic peak hopping on a secondary electron multiplier and static multicollection routines that use 10(13) Omega resistors in the amplifier feedback loop. The high-ohmic resistors also allow the precise and accurate measurement of the minor (272)(UO2) isotopologues (mostly (UOO)-U-238-O-18-O-16) in a static multicollection routine, which permits precise and accurate determination of the O-18/O-16 ratio of UO2 molecules during the U-isotope ratio measurement without compromising signal intensity on the more abundant UO2 isotopologues. This enables the precise determination of U abundances in zircons by isotope dilution with within-run correction of isobaric interferences from the minor UO2 isotopologues, thereby eliminating one of the major sources of uncertainty in ultra-highprecision U-Pb data sets. This approach permits the determination of single U-Pb dates with uncertainties <0.2 parts per thousand and corresponding weighted mean dates with uncertainties <0.1 parts per thousand (n similar to 6 to 10). Furthermore, the ability to use different combinations of detector setups for the same analysis within the same mass spectrometer allows for direct comparison of independently calibrated detector systems.