Methode rb sr dating updating clearcase checkin comments

04-Dec-2018 14:02

The important concept in isotopic tracing is that Sr derived from any mineral through weathering reactions will have the same Sr ratio (and often the Nd-Nd ratios as well) the geological fingerprint of an object or skeleton can be measured, allowing migration patterns to be determined.

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 dates indicate the true age of the minerals only if the rocks have not been subsequently altered.These minerals develop such high Sr ratio of 0.712 could be assumed in all dating studies without introducing significant errors.Such determinations are called model ages because the initial ratio is predicted by a model rather than measured directly.During fractional crystallization, Sr tends to be come concentrated in plagioclase, leaving Rb in the liquid phase.Hence, the Rb/Sr ratio in residual magma may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. Typically, Rb/Sr increases in the order plagioclase, hornblende, K-feldspar, biotite, muscovite.

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

These minerals develop such high Sr ratio of 0.712 could be assumed in all dating studies without introducing significant errors.

Such determinations are called model ages because the initial ratio is predicted by a model rather than measured directly.

During fractional crystallization, Sr tends to be come concentrated in plagioclase, leaving Rb in the liquid phase.

Hence, the Rb/Sr ratio in residual magma may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. Typically, Rb/Sr increases in the order plagioclase, hornblende, K-feldspar, biotite, muscovite.

This, thus, allows a different rate of radiogenic Sr to evolve in the separate rocks and their component minerals as time progresses.