The inheritance of argon seems to be a better model than is the mixing model. For example, Lord Kelvin had estimated the ages of both the Earth and the Sun based on cooling rates. Doesn't this mess up the idea that all lead in zircons must be the result of radioactive decay? In other words, the actual rate of fission track production isn't really known, nor is it known if this rate can be affected by various concentrations of U or other physical factors. It is just too subjective and too open to pitfalls in interpretation to be used as any sort of independent measure of estimating elapsed time. Honda and I.
Dating rocks by radioactive timekeepers is simple in theory, but almost all of the different methods except for the isochron methods - see below rely on these few basic assumptions:
Potassium-Argon Dating Methods
But, how is one to do this if they are so easily confused with true trackways? Nevertheless, it is possible for initial isotope ratio variation to be obscured in a statistically acceptable isochron. Considerable excess 40 Ar measured in ultramafic mantle xenoliths from Kerguelen Archipelago in the southern Indian Ocean likewise is regarded as the mantle source signature of hotspot volcanism. After this came to light, Kelvin admitted that he might just as well have set his original upper limit on the age of the Earth at 4, Ma instead of Ma. The physical procedure for 40 Ar- 39 Ar dating is the same except for three differences:. Aboriginal implements have been discovered in association with the australites. Thus the correctness of the geologic time scale is assumed in deciding which minerals are suitable for dating.