Start Paleontology relative dating

Paleontology relative dating

The dates indicate the true age of the minerals only if the rocks have not been subsequently altered.

The ideal scenario according to Bowen's reaction series would see a granite melt begin crystallizing a cumulate assemblage of plagioclase and hornblende (i.e.; tonalite or diorite), which is low in K (and hence Rb) but high in Sr (as this substitutes for Ca), which proportionally enriches the melt in K and Rb.

This then causes orthoclase and biotite, both K rich minerals into which Rb can substitute, to precipitate.

It is also "the determination of the actual temporal sequence of past events".

Rb-Sr can then be used on the altered mineralogy to date the time of this alteration, but not the date at which the rock formed.

Strontium isotope stratigraphy relies on recognised variations in the Sr ratio of seawater over time.

The application of Sr isotope stratigraphy is generally limited to carbonate samples for which the Sr seawater curve is well defined.

The Rb-Sr dating method has been used extensively in dating terrestrial and lunar rocks, and meteorites.