“This (work) shows unequivocally for the first time that there is indeed a real problem in the uranium/lead evolution in meteorites, in that in each of these meteorites there is now insufficient uranium to support the lead isotope composition.
“It therefore follows that the whole of the classical interpretation of the meteorite lead isotope data is in doubt, and that the radiometric estimates of the age of the Earth are placed in jeopardy.” In plain language, the radiometric estimates for the age of the earth are lacking real foundations.
The radiometric dating method is basically an extrapolation of the form shown in Fig. If the decay constant is known with great accuracy, an extrapolation over one or two thousand years may be regarded as quite reasonable. It should be obvious that the further one projects present rates, the more likely one is to be quite wrong. era started about 1955 with the publication of a classic paper by Patterson In spite of cautions and scepticism advised by the authors this number has been widely and enthusiastically accepted and is usually quoted as if the evidence was decisive and conclusive. Lead-206 and lead-207 are known daughter products from the decay of uranium-238 and uranium-235, respectively.
It has assumed something of the status of a universal constant to which all other data must be fitted, thus it has become common practice to assume that data which does not fit this result is either wrong or unintelligible. Lead-204, a minor isotope of common lead, has no radioactive parent and is believed to be primordial lead.
In case the significance of these results is ignored, a few sentences from the Gale “ …
it is not widely appreciated, outside the ranks of those who work directly in geochronology or meteoritics that, judged by modern standards, the meteoritic lead-lead isochron is very poorly established.
a popularly accepted “universal constant” even though the foundations on which it was based have been virtually removed.
Up until 1972 these could be explained as being contaminated with radiogenic lead from uranium and thorium decay.
In 1972, however, Gale showed unequivocally that there is by no means sufficient uranium and thorium to account for what could previously have been called radiogenic lead.
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.