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Concordia dating

From CreationWiki, the encyclopedia of creation science

Concordia dating is a form of uranium/lead dating that uses a concordia diagram like the one above. The theory is that when zircons crystallize they lose all of their lead and as long as the crystal remains closed its lead/uranium ratios should follow curve in the chart above.

It is further theorized that since all isotopes of the same element are chemically identical, they should be removed in proportional amounts, forming a straight line on the concordia diagram, that crosses the concordia curve at both the crystallization and the contamination date. Loss of uranium moves the point up and to the right, while a loss of lead moves the point down and to the left.

In reality you don't always get a nice neat line, showing that reality is more complicated than indicated by the theory. Furthermore, contamination can total reset the "clock", providing a way to explain data that does not fit the theory.

For Concordia dating the samples must have both the crystallization and the contamination dates, so this provides yet another way to explain data that does not fit the theory.

Concordia dating is based on the following assumptions.

All lead is removed from zircons when they crystallize, such that there are no daughter isotopes present in the original sample. If zircons cooled and crystallized faster than they are thought to have done, then they could have had original lead, and that would throw off the entire process.
All isotopes of the same element are removed in proportional amounts. However, since lighter isotopes move faster than heavier ones at a given temperature, there would be a tendency for lighter isotopes to be removed a little faster.
That the decay rates are constant. However, there is evidence of accelerated decay in the past.

Above is a concordia diagram based on accelerated decay and Biblical creation. While it is not a precise diagram, it illustrates the basic effect that accelerated decay and Biblical creation would have on concordia dating.

Given concordia dating's questionable assumptions and the ability of the theory to explain dates that don't fit the theory, it is reasonable to conclude that concordia dating is not reliable, as it is claimed to be.