ASSESSMENT OF ERRORS IN SIMS ZIRCON U-PB GEOCHRONOLOGY USING A NATURAL ZIRCON STANDARD AND NIST SRM 610 GLASS

Abstract

Analytical errors calculated for individual spot 206Pb/238U measurements of zircon analyzed using high mass resolution secondary ion mass spectrometry (HR-SIMS, e.g., SHRIMP II) were assessed using natural zircon (z6266) and synthetic glass standards (NIST SRM 610). Evidence for U/Pb homogeneity of these materials includes new thermal ionization mass spectrometry (TIMS) U–Pb analyses of 22 fragments of z6266 zircon from two laboratories, which are identical within error and yield a weighted mean 206Pb/238U age of 559.0±0.2 Ma. TIMS U–Pb analyses of the SRM 610 yielded homogeneous 206Pb/238U=0.2566.