“…In zircon, several studies have reported the presence of clusters of Y, Pb and Al (Valley et al , , Peterman et al , Piazolo et al , Blum et al , Peterman et al ). Isolation of these clusters, using 3D volumes defined by isoconcentration surfaces (Hellman et al ) or cluster analysis routines (e.g., Stephenson et al , Dong et al ), significantly reduces the analytical background and permits quantification of compositional and isotopic analysis of these clusters. 207 Pb/ 206 Pb measurements of clusters in both concordant and discordant zircon (Figure ) have been shown to be distinct from bulk isotopic compositions outside the cluster and this has allowed the isotopic compositions of the clusters to be used to constrain the timing of geological events (Valley et al , , Peterman et al ).…”