Age of solar system radioactive dating
Lead-206 and lead-207 are also believed to be present in primordial lead since there is insufficient uranium to account for all the lead.
Just how much lead-206 and 207 were present at the beginning, nobody knows. As a uranium ore ages, the ratio of lead-206 to lead-204 increases as does the ratio of lead-206 to lead-207.
That difficulty aside, they were selected because they contain very little uranium and thorium and are therefore unlikely to contain significant radiogenic lead.
However, it is even more surprising to learn that the lead isotope ratios chosen by Patterson Most meteorites have lead isotope ratios similar to those of present day common lead.
Since the lead in meteorites can no longer be ascribed to uranium/thorium decay, it may also be taken to represent primordial lead.
Therefore, since the lead isotope ratios for the majority of meteorites are the same as present day common lead ratios and may also be assumed to represent primordial lead, the billion year age chronology disappears.
In 1972 this assumption was shown to be highly questionable.It might be argued that although radiometric dating has a few problems, the large body of concordant data using different isotopes shows that the dates are of the right order.In fact, there is no large body of concordant data.It is probably because of this type of evidence for extensive mixing in the alteration zone that Patterson “In view of the evidence for extensive mixing, it would seem contrary to the facts to postulate differing frozen lead/uranium ratios that have existed for billions of years.The requirements of the assumptions in the lead ore method are so extreme it is unlikely that it should give a correct age.” So they took a different approach.
Some evidence is also presented to show that radiometric results that are in agreement with the accepted geological time scale are selectively published in preference to those results that are not in agreement.