Arndts and Overn (8) and Kramer as well as others (78) declare that Rb-Sr isochrons would be the total consequence of blending, as opposed to of decay of 87 Rb over very long periods:
It really is clear that mixing of pre-existent materials will produce a linear variety of isotopic ratios. We require maybe maybe not assume that the isotopes, assumed become child isotopes, had been in reality stated in the stone by radioactive decay. Therefore the presumption of enormous many years is not proven.
(8, p. 6)
These writers observe that it’s mathematically feasible to make a straight line for a Rb-Sr isochron diagram by combining, in a variety of proportions, two end people in various 87 Sr/ 86 Sr and 87 Rb/ 86 Sr compositions.