Fig. 3From: U–Th isotopic microanalysis of zircon reference materials and KBSI working standardsa Comparison between 232Th/238U ratios calculated using SHRIMP 208Pb/206Pb data and the assumption that the U–Pb and Th–Pb isotopic systems in the zircons are concordant (232Th/238UCONCORDANCE) and those calculated by the SQUID program (232Th/238USQUID). b The frequency histogram of 232Th/238UCONCORDANCE ratios for the 91500 zirconBack to article page