How does radioactive dating help determine the age of fossils dating site in in the world 2018
For an isochron to be valid, each sample tested must (1) have had the same initial ratio, (2) have been a closed system over geologic time, and (3) have the same age.
Well-preserved, unweathered rocks that crystallized rapidly and have not been subjected to major reheating events are most likely to give valid isochrons.
On the other hand, meteorites that have spent most of their time in the deep freeze of outer space can provide ideal samples.
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.
Strontium and rubidium are extracted and loaded into the mass spectrometer, and the values appropriate to the , the data are examined to assess how well they fit the required straight line.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.When minerals with a low-rubidium or a high-strontium content are analyzed, the isochron-diagram approach can be used to provide an evaluation of the data.As a liquid rock cools, first one mineral and then another achieves saturation and precipitates, each extracting specific elements in the process.Strontium is extracted in many minerals that are formed early, whereas rubidium is gradually concentrated in the final liquid phase.