The key effects of redox modifications in planetary evolution | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  The key effects of redox modifications in planetary evolution

Wednesday 25 March 2015
Séminaires Géochimie
Rita Cicconi
(Universität Erlangen-Nürnberg)
Extrait: 

The differentiation of terrestrial planets is not only related to changes in density and pressure or in fact solely to physical properties, but also to redox mechanisms. Studies into the redox state of magmas provide important constrains on the formation and evolution of planetary bodies. Moreover, since oxygen fugacity is a key parameter in controlling the physical and chemical style of interactions between reservoirs within the mantle and between the mantle and surface, it follows that redox mechanisms play a key role in determining the dynamics of the (inner and outer) terrestrial planets.
The redox conditions that have accompanied basalt evolution on planetary bodies are known to be different, albeit with some similarities. The strongly reducing environments of the moon and meteorites have led to significant amounts of reduced species, whereas analogous terrestrial materials predominantly contain the corresponding oxidized valences. Important geochemical elements such as Fe, Cr, V, Ce and Eu, exist in magmatic systems with different valences and coordination geometries. Of particular importance is developing an understanding of the factors influencing redox mechanisms since the geochemical behaviour of these multivalent elements reflects the oxygen fugacity of the environment, and can affect mineral assemblage, element partitioning, mass transfers processes and rheology of the melts.
In this talk, some examples on studies of multivalent elements in silicate glasses will be presented and answers to some pertinent questions will be provided. How can we study them? And which factors are driving forces in changing the redox state of the earth systems? Moreover, we will see how these studies can be related to the development of technological glasses, such as in the framework of extra-clear glasses, fining processes, and solar cells.