Start St rb dating

St rb dating

Ils se substituent en partie au potassium pour le rubidium et au calcium pour le strontium.

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

The resulting Rb-Sr ratios and Rb and Sr abundances of both the whole rocks and their component minerals will be markedly different.

Elle est liée à une autre constante caractéristique de cette désintégration, T, appelée « demi-vie », temps au bout duquel il ne reste plus que la moitié de l'isotope présent au départ.

However, because Rb substitutes for K in minerals and these minerals have different K/Ca ratios, the minerals will have had different Rb/Sr ratios.

The utility of the rubidium-strontium isotope system results from the fact that Sr with a half life of 48.8 billion years.

In addition, Rb is a highly incompatible element that, during partial melting of the mantle, prefers to join the magmatic melt rather than remain in mantle minerals. The radiogenic daughter, Sr, is produced in this decay process and was produced in rounds of stellar nucleosynthesis predating the creation of the Solar System.

Il arrive que le strontium soit un élément majeur de certains minéraux, c'est le cas notamment du carbonate de strontium de formule Sr COSr qui, lui, est un isotope stable du strontium comme le sont, d'ailleurs, les trois autres.