Start Rb dating site

Rb dating site

There are various petrogenetic explanations for the generation of peralkaline felsic magmas.

To further investigate the unusual trace element characteristics of the Olkaria rocks, notably the Sr depletion and enrichments in Rb, U and Th, the O, Ar, Nd, Pb, Rb–Sr and U–Th isotope systematics were determined on glasses and minerals.

Inferred high magma fractionation rates of up to 2·5 × 10/yr are comparable with those for much larger metaluminous silicic magma systems.

Magma storage times (∼22 ky), however, are much shorter and may best be accounted for by the specific size, longevity and thermal gradient of the silicic magma system., 1994).

In contrast, glasses and minerals yield U–Th isochrons of 25 ± 10 ka and are probably controlled by the Th-enriched accessory phase chevkinite.

We therefore ascribe the pre-eruptive age information to crystallization of the observed phenocryst phases.

According to this model, initiation of the recent comendite eruptions at ∼20 ka followed the deposition of a welded pantelleritic deposit.

The Olkaria comendites were stratigraphically divided into a Lower, Middle and Upper Member and the most recent Ololbutot comendites.

Comparison of the two isotope systems therefore may provide additional insights into the time scales of processes that control the evolution of strongly differentiated silicic magmas.