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Water as a trace co...
Water as a trace component in mantle pyroxene: Quantifying diffusion, storage capacity and variation with geological environment
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- Sundvall, Rickard, 1976- (författare)
- Stockholms universitet,Institutionen för geologiska vetenskaper
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- Skogby, Henrik, Docent (preses)
- Enheten för mineralogi, Naturhistoriska riksmuseet, Box 50007, 10405 Stockholm
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- Skelton, Alasdair, Professor (preses)
- Stockholms universitet,Institutionen för geologiska vetenskaper
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visa fler...
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- Libowitzky, Eugen, Associate Professor (opponent)
- Institut für Mineralogie und Kristallographie, Universität Wien, Geozentrum, Althanstrasse 14, A-1090 Wien
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visa färre...
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(creator_code:org_t)
- ISBN 9789174470659
- Stockholm : Department of Geological Sciences, Stockholm University, 2010
- Engelska 27 s.
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Serie: Meddelanden från Stockholms universitets institution för geologiska vetenskaper ; 338
- Relaterad länk:
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https://urn.kb.se/re...
Abstract
Ämnesord
Stäng
- In this study, distribution and diffusion of water in pyroxene are examined in an effort to explain the water content variation observed in natural pyroxene. Water is a common trace component in many nominally anhydrous minerals (NAMs) from the Earth's crust and mantle and greatly impacts their physical properties. Therefore, it is crucial to constrain the processes that control water incorporation in these minerals. The pyroxene group has a fairly simple mineral chemistry, the highest amount of water and the greatest water content variation measured in mantle NAMs. Therefore, they are ideal for a case study such as the present. The redox reaction: OH- + Fe2+ ↔ O2- + Fe3+ + ½H2, is believed to control water diffusion in many NAMs having sufficiently high iron contents. Nevertheless, reactions involving vacancies and charge-deficient substitutions which are mainly controlled by cation diffusion are also present and have reaction kinetics that is significantly slower than the redox exchange. Therefore, diffusion and reaction kinetics were studied in (1) synthetic diopside with ~0.7 wt % FeO which allows the study of contributions from both types of reactions (i.e. Fe-redox and cation diffusion). These results were then compared (2) with reaction kinetics in pure synthetic diopside. The diffusion rates are faster in Fe-free diopside, as reaction kinetics is dominated by cation diffusion in samples with low Fe contents. Next (3), water content variation and zonation were investigated in natural pyroxene using high resolution FTIR imaging. The results show no water zonation and a correlation between mantle source and water content. Finally (4), thermal annealing experiments in H2 on natural pyroxene show little or no re-hydration capacity for mantle samples. Altogether, the results indicate that the water contents of most mantle pyroxenes do reflect mantle conditions and that many types of reactions controlling water uptake and release seem to be present in pyroxene.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
Nyckelord
- pyroxene
- mantle mineralogy
- water in nominally anhydrous minerals
- iron redox-reaction
- kinetics
- water zonation
- FTIR imaging
- re-hydration capacity
- Mineralogy
- Mineralvetenskap
- Mineralogy, Petrology and Geochemistry
- mineralogi, petrologi och geokemi
Publikations- och innehållstyp
- vet (ämneskategori)
- dok (ämneskategori)
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