Rubidium strontium dating method black single dating london
Weathering is a disturbing influence, as is leaching or exchange by hot crustal fluids, since many secondary minerals contain rubidium.Volcanic rocks are most susceptible to such changes because their minerals are fine-grained and unstable glass may be present.In most cases, the changes in the Sr ratio are so large that an initial value can be assumed without jeopardizing the accuracy of the results.
Potassium-bearing minerals including several varieties of mica, are ideal for rubidium–strontium dating as they have abundant parent rubidium and a low abundance of initial strontium.Three of the analyzed samples (H6, KQ1 and TZ67) generated Rb-Sr isochron ages of 141 ± 61 Ma, 332 ± 32 Ma and 235 ± 8 Ma (errors quoted at 2σ), respectively.These results are similar to the corresponding K-Ar ages (125 Ma, 389 Ma and 234 Ma).In the 1950s, when mass spectrometers following Nier’s design were constructed for the isotope analysis of solids, the Rb-Sr dating method became widely used, the concentrations of these elements being determined by isotope dilution and also as a result of separation by cation exchange chromatography.
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This difference may appear small, but, considering that modern instruments can make the determination to a few parts in 70,000, it is quite significant.