@article{GGR:GGR914,
author = "Lutz Nasdala and Wolfgang Hofmeister and Nicholas Norberg and James M. Martinson and Fernando Corfu and Wolfgang D{\"o}rr and Sandra L. Kamo and Allen K. Kennedy and Andreas Kronz and Peter W. Reiners and Dirk Frei and Jan Kosler and Yusheng Wan and Jens G{\"o}tze and Tobias H{\"a}ger and Alfred Kr{\"o}ner and John W. Valley",
abstract = "We introduce and propose zircon M257 as a future reference material for the determination of zircon U-Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS-determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for 206pb/238U and 0.7392 ± 0.0003 for 207pb/235U. Its 206pb/238U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U-Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ∼ 840 μg g−1 U (Th/U ∼ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit-cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U-Pb age, and the calculated alpha fluence of 1.66 × 1018 g−1. This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc-silicate skarn.",
doi = "10.1111/j.1751-908X.2008.00914.x",
issn = "1751-908X",
journal = "Geostandards and Geoanalytical Research",
keywords = "zircon, reference material, M257, U-Pb, geochronology, SIMS, secondary ion mass spectrometry",
number = "3",
pages = "247--265",
publisher = "Blackwell Publishing Ltd",
title = "{Z}ircon {M}257 - a {H}omogeneous {N}atural {R}eference {M}aterial for the {I}on {M}icroprobe {U}-{P}b {A}nalysis of {Z}ircon",
url = "http://dx.doi.org/10.1111/j.1751-908X.2008.00914.x",
volume = "32",
year = "2008",
}