Skip to Main Content
Book Chapter

Processes of silicic melt generation

By
Published:
January 01, 2008

Abstract

Uranium-series isotopes provide important constraints on the timescale of magma differentiation and this can be used to identify where in the crust and silicic magmas acquire their geochemical characteristics. Timescales of differentiation can be inferred from the observed co-variations of U-series disequilibria with differentiation indexes. When crustal assimilation of secular equilibrium material is involved, inferred timescales will generally decrease. In turn, they will increase if periodical recharge (>20 wt% relative volume) of the magma body occurs. If crustal assimilation and magma recharge occur concurrently, inferred timescales for differentiation can be similar to that of closed system differentiation. We illustrate the approach with data from Mount St Helens which suggest that dacitic compositions are produced in c. 2000 years. Combining this with recent evidence for an important role for amphibole fractionation suggests that differentiation of a c. 10 km3 magma body at this volcanic centre occurs at 8–10 km depth in the crust.

You do not currently have access to this article.

Figures & Tables

Contents

Geological Society, London, Special Publications

Dynamics of Crustal Magma Transfer, Storage and Differentiation

Catherine Annen
Catherine Annen
University of Geneva, Switzerland
Search for other works by this author on:
Georg F. Zellmer
Georg F. Zellmer
Academia Sinica, Taipei, Taiwan
Search for other works by this author on:
Geological Society of London
Volume
304
ISBN electronic:
9781862395527
Publication date:
January 01, 2008

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal