The same mount was also analyzed by Geological Survey of Canada (GSC) researchers using the GSC SHRIMP II ion microprobe (Stern and Amelin, 2003).In our comparison, we determined that variations in U and Pb instrumental fractionation, sputter yield, detection efficiency (useful yield) and analytical reproducibility are very similar for both, the UCLA and GSC instruments, despite prominent differences in design and analytical conditions.Reproducibility on z6266 is slightly lower than the ~3% standard deviation that we and others (Schmitz et al., 2003) typically observe for replicate analyses of our currently used standard AS3, for reasons that remain as yet unresolved.
This suggests that variations in interelement fractionation during ion bombardment are largely independent of instrumental design and that interelement fractionation in ion microprobe U-Pb analysis can be monitored to an external reproducibility of ~1-2%.
WE SPECIALISE IN PRECISE, ACCURATE, HIGH SPATIAL RESOLUTION, URANIUM-THORIUM-LEAD GEOCHRONOLOGY OF ZIRCON, MONAZITE, XENOTIME, TITANITE, ALLANITE, COLUMBITE-TANTALITE, BADDELEYITE, RUTILE, CASSITERITE, OPAL, APATITE, PEROVSKITE, GADOLINITE, CHEVKINITE, ILMENORUTILE, URANINITE AND ZIRCONOLITE.
SHRIMP U-Pb ages and Ti-in–zircon thermometry of Jack Hills and Mount Narryer zircon have provided constraints on the crystallisation environment of zircon from the earliest Hadean Earth.
This means that even older crust exists that hosted these igneous rocks!
Anyway, U-Pb is used to look at old rocks, usually in the millions to billions of years old.