Arndts and Overn (8) and Kramer yet others (78) declare that Rb-Sr isochrons would be the total consequence of blending, as opposed to of decay of 87 Rb over long stretches:
It really is clear that blending of pre-existent materials will produce an array that is linear of ratios. We are in need of maybe perhaps perhaps not assume that the isotopes, assumed become child isotopes, had been in reality manufactured in the stone by radioactive decay. Therefore the assumption of enormous ages is not proven.
(8, p. 6)
These writers keep in mind that its mathematically possible to make a right line for a Rb-Sr isochron diagram by combining, in a variety of proportions, two end users of various 87 Sr/ 86 Sr and 87 Rb/ 86 Sr compositions.
A test often used to check on for blending is always to plot the 87 Sr/ 86 Sr ratio against 1/Sr (49).
This plot shows if the 87 Sr/ 86 Sr ratio differs methodically aided by the Sr content associated with the various examples analyzed, as is the situation in the event that isochron had been due to combining in place of radioactive to decay with time.