Problems in the radioisotope dating method
U leakage would cause discordant points to plot above the cocordia. Lunar rocks also lie on the Geochron, at least suggesting that the moon formed at the same time as meteorites. Pb separated from continents and thus from average crust also plots on the Geochron, and thus suggests that the Earth formed at the same time as the meteorites and moon.
But, again, exptrapolation of the discordia back to the two points where it intersects the Concordia, would give two ages - t* representing the possible metamorphic event and t and solve for t . This argument tells when the elements were formed that make up the Earth, but does not really give us the age of the Earth. Thus, our best estimate of the age of the Earth is 4.55 billion years.
Kevin Rogers submitted a comment to that article (reproduced below, edited to focus on substantive issues), to which Dr Jim Mason replies.
Radioactive Dating Methods I am Kevin Rogers and am the director of Reasonable Faith Adelaide.
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.
Any age calculated is based on multiple unprovable assumptions to match the long-age worldview.
Zircon has a high hardness (7.5) which makes it resistant to mechanical weathering, and it is also very resistant to chemical weathering. Chemically, zircon usually contains high amounts of U and low amounts of Pb, so that large amounts of radiogenic Pb are produced.
Other minerals that also show these properties, but are less commonly used in radiometric dating are Apatite and sphene.
These 3 methods can be checked against each other, especially using the Concordia line/diagram.We can also construct a Concordia diagram, which shows the values of Pb isotopes that would give concordant dates.The Concordia curve can be calculated by defining the following: ).It can be experimentally confirmed that molten Zircon rejects lead.This is highly significant, as it means that the initial conditions are known to a high level of confidence.