Rubidum strontium dating
The utility of the rubidium-strontium isotope system results from the fact that Sr with a half life of 48.8 billion years.In addition, Rb is a highly incompatible element that, during partial melting of the mantle, prefers to join the magmatic melt rather than remain in mantle minerals. The radiogenic daughter, Sr, is produced in this decay process and was produced in rounds of stellar nucleosynthesis predating the creation of the Solar System.Part 1 (in the previous issue) explained how scientists observe unstable atoms changing into stable atoms in the present.Part 2 explains how scientists run into problems when they make assumptions about what happened .Most people think that radioactive dating has proven the earth is billions of years old.Yet this view is based on a misunderstanding of how radiometric dating works.Rubidium 87 decays to Strontium 87 with a half life of xx my.Rubidium and strontium are reasonably abundant and the decay is not branched, unlike potassium-argon.
However, because Rb substitutes for K in minerals and these minerals have different K/Ca ratios, the minerals will have had different Rb/Sr ratios.
An hourglass is a helpful analogy to explain how geologists calculate the ages of rocks.
When we look at sand in an hourglass, we can estimate how much time has passed based on the amount of sand that has fallen to the bottom.
Sr) was the first widely used dating system that utilized the isochron method.
Rubidium is a relatively abundant trace element in Earth’s crust and can be found in many common rock-forming minerals in which it substitutes for the major element .
The method is applicable to very old rocks because the transformation is extremely slow: the half-life, or time required for half the initial quantity of rubidium-87 to disappear, is approximately 50 billion years.