I commonly find that detrital zircon samples analysed by LA-ICP-MS display discordia arrays, in Wetherill space, that plot toward the origin. This implies some form of recent lead loss - a topic most recently addressed by Pidgeon et al 2017 and Andersen et al 2019. In TW space, these analyses also imply recent lead loss. I typically observe these effects in older zircons, typically older than c. 1.5 Ga (arbitrary age). Could this be because older zircons are typically more vulnerable to lead loss? I do not think this is the case. Instead, I think it is simply because discordia arrays are exaggerated for older upper intercept ages and therefore more noticeable. A supporting question to my main question, then, is what does lead contamination during analysis look like in comparison to recent lead loss in Wetherill and TW space, assuming such contamination is allowed to pass through the data reduction process?
I think it is safe to say that older zircons are more vulnerable to Pb loss. This is especially so for those with higher U concentrations (>400 ppm). This longer time combined with the more decay destruction of the lattice contributes to the opportunity for lead loss.
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