title: Uranium-lead dating method at the Pará-Iso isotope geology laboratory, UFPA, Belém - Brazil.
abstract: Analytical procedures for U-Pb isotope dilution analyses at the Pará-Iso isotope geology laboratory of the Federal University of Pará (UFPA) are described in detail. The procedures are applied to zircon, titanite, rutile, apatite, columbite-tantalite and whole rock. Reagent preparation and chemical processing are done in clean-room conditions. Samples are dissolved using Teflon microcapsules in steel jacket Teflon Parr Instrument bomb or Teflon screw cap containers. U and Pb are separated using anion exchange AG 1 x 8 resin columns. Typical blanks for mineral sample amounts of 0.01 to 1.0 mg are less than 1 pg U and 20-30 pg Pb. Isotope analysis of the U and Pb from the same filament are carried out using a Finnigan MAT 262 mass-spectrometer in static and dynamic modes. The current analytical level is demonstrated on analyses of international standard zircon 91500 with three different 235U-205Pb and 235U-208Pb isotope tracers and whole rock standards. Results of analyses of two zircon samples are also presented.
authors.affiliation: Centro de Geociências, Pará-Iso, Universidade Federal do Pará, Belém, PA, 66075-110, Brasil.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Krymsky
authors.forename: Moacir J B
authors.initials: MJ
authors.lastname: Macambira
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Lafon
authors.forename: Gérson S
authors.initials: GS
authors.lastname: Estumano