Plešovice zircon — A new natural reference material for U–Pb and Hf isotopic microanalysis

• Published in: Chemical geology Vol. 249; no. 1; pp. 1 - 35
• Main Authors: Sláma, Jiří, Košler, Jan, Condon, Daniel J., Crowley, James L., Gerdes, Axel, Hanchar, John M., Horstwood, Matthew S.A., Morris, George A., Nasdala, Lutz, Norberg, Nicholas, Schaltegger, Urs, Schoene, Blair, Tubrett, Michael N., Whitehouse, Martin J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-03-2008
• Subjects: Bohemian Massif; Hf isotopes; Laser ablation ICP-MS; NATURAL SCIENCES; NATURVETENSKAP; Plesovice; Plešovice; U-Pb dating; Zircon reference material; Zircon reference material; Hf isotopes; Bohemian Massif; Plešovice; Laser ablation ICP-MS; U–Pb dating
• ISSN: 0009-2541; 1872-6836; 1872-6836
• DOI: 10.1016/j.chemgeo.2007.11.005

Matrix-matched calibration by natural zircon standards and analysis of natural materials as a reference are the principle methods for achieving accurate results in microbeam U–Pb dating and Hf isotopic analysis. We describe a new potential zircon reference material for laser ablation ICP-MS that was extracted from a potassic granulite facies rock collected in the southern part of the Bohemian Massif (Plešovice, Czech Republic).
Data from different techniques (ID-TIMS, SIMS and LA ICP-MS) and several laboratories suggest that this zircon has a concordant U–Pb age with a weighted mean
206Pb/
238U date of 337.13
±
0.37 Ma (ID-TIMS, 95% confidence limits, including tracer calibration uncertainty) and U–Pb age homogeneity on the scale used in LA ICP-MS dating. Inhomogeneities in trace element composition due to primary growth zoning prevent its use as a calibration standard for trace element analysis. The content of U varies from 465 ppm in pristine parts of the grains to ~
3000 ppm in actinide-rich sectors that correspond to pyramidal faces with a high degree of metamictization (present in ca. 30% of the grains). These domains are easily recognized from high intensities on BSE images and should be avoided during the analysis. Hf isotopic composition of the Plešovice zircon (>
0.9 wt.% Hf) is homogenous within and between the grains with a mean
176Hf/
177Hf value of 0.282482
±
0.000013 (2SD). The age and Hf isotopic homogeneity of the Plešovice zircon together with its relatively high U and Pb contents make it an ideal calibration and reference material for laser ablation ICP-MS measurements, especially when using low laser energies and/or small diameters of laser beam required for improved spatial resolution.