► Ages calculated with the currently accepted value need revision and will become older by 2%.
The utility of the rubidium-strontium isotope system results from the fact that different minerals in a given geologic setting can have distinctly different Sr.
For example, consider the case of a simple igneous rock such as a granite that contains several major Sr-bearing minerals including plagioclase feldspar, K-feldspar, hornblende, biotite, and muscovite.
2.5 Ga yields an unweighted mean λRb decay constant is 2% lower than the currently accepted value.
► Our value of 1.394 ±0.004 ×10-11yr-1 agrees with the results of the most recent age comparisons and the latest beta counting experiment.
The accuracy of Rb–Sr ages, however, strongly depends on the accuracy of the U by comparing Rb–Sr ages of minerals with U–Pb ages obtained from the same intrusion.