Disadvantages of rubidium strontium dating
It has been used to date meteorites (e.g., Minster and Allègre ).Hence, Rb–Sr dating has greatly contributed to developing an emerging idea of our environment: an evolving and ever changing planet.To ensure accurate results for isochron relationships, the Rb–Sr of a sample should directly be determined in the same sample cut as the one used for Sr isotope analysis so that the amount of Rb directly corresponds to the radiogenic ingrowth of Sr.The method of isotope dilution is currently the most precise and accurate way to obtain this ratio in conjunction with Sr isotope analyses; a precision of ~0.1–0.2 % on Sr values can be obtained.
For this, both Rb and Sr must be separated from the rock matrix and from each other to avoid matrix effects during the isotope analyses and, more importantly, isobaric interferences of Sr-87 and Rb-87, which will both be detected as mass 87.
: Common expression of the intercept of the isochron with the ordinate in a Nicolaysen diagram that marks the strontium isotope composition at the time of formation which, by definition, is that of all phases contributing to the isochron.
The Rb–Sr dating technique is among the most widely used and most powerful dating tools available in Earth sciences.
Ideally more than two samples are used for this concept to ensure that the regression line indeed reflects an age; the more samples that are used in a Nicolaysen diagram plot, the more likely it is that the regression is geologically meaningful.
Obviously, for two samples a regression can be calculated, even though both samples may not be related to each other, rendering any calculated age (or initial isotope composition) of such “two-point” isochrons potentially dubious without any independent age indicators.50 ng Sr by thermal ionization mass spectrometry (TIMS) to within 40 ppm.