Isochron dating gives unreliable results (Talk.Origins)

Claim CD014:


 * Isochron dating is unreliable. The method assumes that the samples are cogenetic, i.e., that they form at the same time from a reasonably homogeneous common pool. This assumption is invalid. In particular, mixing two sources with different isotopic compositions gives meaningless but apparently valid isochron plots.

Source: Overn, William, n.d. Isochron rock dating is fatally flawed.

CreationWiki response:

First of all, how often are dates that agree with what the Evolutionist expects checked for evidence of mixing? There would be more motivation for checking when one does not like the results.

Second, mixing is not the only way of getting false isochrons.

Maybe they do and simply are not published often enough. Furthermore, mixing is not the only way of getting false isochrons.

This really does not help Talk.Origins' case any, besides they left out two other factors that can produce false isochrons:
 * Open systems. Also known as contamination.
 * Isotopic Fractionation. It is a physical separation of isotopes and it can be caused by heating and cooling, water flow, contact between high and low concentration magma and just normal molecular motion. Evidence for Isotopic Fractionation does show up in isotopic data so it is a factor that needs to be considered.

Yet, an otherwise good isochron will be dismissed as from an open system (contamination) simply because it does not agree with the date determined by the fossils in the material being dated. The fact is that such methods for guarding against false isochrons can and do fail. The ultimate determining factor is the date indicated by fossils.

Reference: New Age Data of Buried Peat Deposits from the Site "Fili Park"