Change search
ReferencesLink to record
Permanent link

Direct link
Water as a trace component in upper mantle pyroxenes
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2008 (English)In: EURISPET (European Intensive Seminars in Petrology) – Petrology of the lithosphere in extensional settings. Budapest, August 21-31, 2008, 2008Conference paper (Other academic)
Abstract [en]

Hydrogen is a widespread trace element in many nominally anhydrous minerals (NAMs) from the Earth's crust and mantle. Hydrogen is normally incorporated in the form of hydroxyl ions and can be regarded as structurally bound water. The most important minerals of the upper mantle: olivine, orthopyroxene, clinopyroxene and garnet, all contain small but significant amounts of hydrogen, and the upper mantle has a capacity to store the equivalent of several world oceans. The main objective of this project is to investigate in detail the mechanisms that are responsible for water incorporation in upper mantle pyroxenes (and synthetic analogues) as pyroxenes can carry substantial amounts of water, up to 1300 wt ppm H2O. Fundamental questions are how much of the original xenolith water that is lost during transport to the surface and if the spectroscopic features measured in the minerals are representative for mantle conditions. The redox reaction: Fe2+ + OH- ↔ Fe3+ + O2- + ½H2, which is relatively fast, is thought to be the dominant hydrogen exchange reaction in many minerals (Ingrin & Skogby, 2000). The reaction is fast enough to suggest that water in NAMs equilibrates with the transporting magma and related fluids during ascent to the surface. Nevertheless, several studies show systematic variations in water content with geological environment (Bell & Rossman, 1992; Peslier et al., 2002), implying a complex relationship between host mineral, mantle source region, magma type and eruption style. The current part of the project  is focused on the dehydration-hydration mechanisms in diopside, the most common variety of clinopyroxene in the upper mantle. The approach has been to study the kinetics and temperature dependence of the reactions controlling hydrogen diffusion in synthetic Fe-poor diopside. Other reactions are likely to be obscured by the iron redox reaction if measured in natural mantle diopside containing several wt% FeO. Therefore, synthetic diopside with very low amounts (0.7 wt% FeO) of iron had to be used in order to measure the influence and co-dependence of the iron redox reaction with other possible reactions.

Place, publisher, year, edition, pages
National Category
Research subject
Mineralogy, Petrology and Geochemistry
URN: urn:nbn:se:su:diva-29036OAI: diva2:228819
Available from: 2009-08-06 Created: 2009-08-06 Last updated: 2012-02-01Bibliographically approved

Open Access in DiVA

No full text

By organisation
Department of Geology and Geochemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 18 hits
ReferencesLink to record
Permanent link

Direct link