Rb sr method of dating
This relative abundance is expressed as the Sr ratio, where strontium-86 is chosen to represent the stable isotopes strontium-88, strontium-86, and strontium-84, which occur in constant proportions in natural materials.
Thus, a precise measurement of the Sr ratio in a modern volcano can be used to determine age if recycled older crust is present.
So we have every reason to think that rocks when they form do incorporate strontium, and Sr in particular.
However, there is still a way to extract a date from the rock.
Now consider the distribution of the two strontium isotopes Sr.
Because they are chemically indistinguishable, they will appear in the same ratio in every mineral at the time when it is formed: some minerals will have more strontium, some will have less, but all must necessarily have the same The initial state of the rock may therefore be schematically represented by the graph to the right, which shows the initial states of four minerals imaginatively named A, B, C, and D.
Sr) was the first widely used dating system that utilized the isochron method.Therefore it is more convenient to convert this number to an isotope ratio by dividing through by Sr method was first used in geochronology, the poor precision attainable in mass spectrometry limited the technique to the dating of Rb-rich minerals such as lepidolite.These minerals develop such high Sr ratio of 0.712 could be assumed in all dating studies without introducing significant errors.The energies involved are so large, and the nucleus is so small that physical conditions in the Earth (i.e. The rate of decay or rate of change of the number N of particles is proportional to the number present at any time, i.e.The half-life is the amount of time it takes for one half of the initial amount of the parent, radioactive isotope, to decay to the daughter isotope.