The technique does have the added advantage that if the ‘ages’ from both the 238U and 235U chains agree with each other, it adds support to the hypothesis that both chains have experienced the same effects during the formation and lifetime of the crystal. ’ The claim is that if a rock undergoes a metamorphic process then some of the U or Pb from the zircon would be lost, which means the ages would no longer be concordant.A colleague, Dr Tas Walker, advises that, “the Concordia technique arose from the fact that the two U decay series should give the same ‘age’ but almost always they didn’t—i.e. So, where the top part of the line through the zircons intersects the Concordia curve is said to be the ‘age’ of the zircon.
It can be experimentally confirmed that molten Zircon rejects lead.
At their request, physicist Dr Jim Mason, of CMI Canada, reviewed the material from the meeting and his response was published on 2 April 2015 (see Response to Geochronology: Understanding the Uncertainties, a presentation by Dr Justin Payne).
We previously reported an event organized by the Adelaide, Australia, Chapter of Reasonable Faith where Dr Justin Payne, a lecturer within the School of Earth and Environmental Sciences at the University of Adelaide, sought to ‘disprove’ objections to long-age radiometric dating.
He has equipment at the University of Adelaide and does the dating analysis himself.
Thus he has the knowledge of an experienced practitioner and is not just an armchair theoretician.