Ž . Chemical Geology 182 2002 605–618 www.elsevier.comrlocaterchemgeo U–Pb dating of detrital zircons for sediment provenance studies —a comparison of laser ablation ICPMS and SIMS techniques Jan Kosler a, ) , Hege Fonneland b , Paul Sylvester a , Mike Tubrett a , ˇ Rolf-Birger Pedersen b a Department of Earth Sciences, Memorial UniÕersity of Newfoundland, St John’s, NF A1B3X5 Canada b Geologisk Institutt, UniÕersitetet i Bergen, 5007 Bergen, Norway Accepted 20 June 2001 Abstract Ž . New developments in U–Pb dating of zircons by laser ablation LA ICPMS are described and, for the first time, a direct comparison of detrital zircons dated by LA ICPMS and SIMS methods is presented. True real-time mass bias correction is made by aspirating a TlrU tracer at the same time as laser ablation. The method is similar to that described in Horn et al. Ž . 233 235 2000 , except that enriched U rather than U is used in the tracer solution. Correction for laser-induced PbrU elemental fractionation is based on a mathematical treatment of time-resolved data that is independent of laser ablation characteristics and does not require external standardisation. Internal corrections for mass bias and elemental fractionation eliminate the effects of variable sample matrix on isotopic ratios and improve the accuracy of U–Pb dating by laser ablation ICPMS. With the proper error propagation, the precision of U–Pb age determinations is only slightly worse than SIMS-based ion probe dating. However, LA ICPMS is capable of much more rapid analysis of the large number of zircons required for sediment provenance studies. There is excellent agreement between concordant laser ablation ICPMS and SIMS Ž . analyses of detrital zircons extracted from lower Silurian metasandstone from the Ulven Group Skarfjell Formation in the west Norwegian Caledonian nappes. Both LA ICPMS and SIMS U–Pb zircon ages indicate that sedimentary detritus of the Ulven Group was supplied from a terrain containing zircons of Archean, Proterozoic and early Ordovician age. q 2002 Elsevier Science B.V. All rights reserved. Keywords: Sediment provenance; U–Pb zircon geochronology; Laser ablation ICPMS; SIMS; Instrument mass bias 1. Introduction Analysis of the heavy mineral fraction of clastic sediments has proven to be a useful tool for strati- graphic correlations, especially in sedimentary se- quences lacking biostratigraphical markers, strati- ) Corresponding author. Department of Geochemistry, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic. Ž . E-mail address: jkosler@sparky2.esd.mun.ca J. Kosler . ˇ graphically distinct horizons or other time constraints such as are cross-cutting dykes or sills. In addition, heavy mineral assemblages present in clastic sedi- ments may record sediment sources andror transport and depositional histories. Age dating of clastic heavy minerals, particularly zircon and monazite, is, there- fore, a powerful tool in sedimentary provenance studies. Previous studies of sedimentary provenance that Ž utilised U–Pb dating of detrital zircons Morton et 0009-2541r02r$ - see front matter q 2002 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2541 01 00341-2