These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.
The isotope concentrations can be measured very accurately, but isotope concentrations are not dates.
To derive ages from such measurements, unprovable assumptions have to be made such as: There is plenty of evidence that the radioisotope dating systems are not the infallible techniques many think, and that they are not measuring millions of years. For example, deeper rocks often tend to give older “ages.” Creationists agree that the deeper rocks are generally older, but not by millions of years.
Geologist John Woodmorappe, in his devastating critique of radioactive dating, points out that there are other large-scale trends in the rocks that have nothing to do with radioactive decay.
These techniques, unlike carbon dating, mostly use the relative concentrations of parent and daughter products in radioactive decay chains.
For example, potassium-40 decays to argon-40; uranium-238 decays to lead-206 via other elements like radium; uranium-235 decays to lead-207; rubidium-87 decays to strontium-87; etc.
The rate of decay of N in 5,730 years (plus or minus 40 years).
It does not give dates of millions of years and when corrected properly fits well with the biblical flood.
There are various other radiometric dating methods used today to give ages of millions or billions of years for rocks.
That is, they take up less than would be expected and so they test older than they really are.
Furthermore, different types of plants discriminate differently.