Inhaltsbereich
Dense hydrous silicates
Experimental studies have shown that a number of dense hydrous silicates are stable at mantle pressures, corresponding to depths greater than 200 km: e.g. phase A, phase B, phase E, superhydrous phase B. If present in the Earth’s mantle these minerals are important hosts for H2O and their dehydration at much higher P and T may be responsible for deep focus earthquakes. To understand the Earth’s water cycle it is important to learn more about their stabilities and phase relations at P and T.
We synthesize dense hydrous silicates and apply Raman- and IR-spectroscopy (NIR – FIR) as well as X-ray diffraction at ambient conditions and in-situ as a function of pressure, and/or temperature in order to shed light on the crystal chemistry, the structural state and phase relations. In parallel we use atomic-scale modeling techniques to understand the P-/T-induced structural changes.
© GFZ Potsdam- Selected phases in the system MgO-SiO2-H2O. Coloured are Dense Hydrous Magnesium Silicates (DHMS) of which only 10Å phase has been found in nature yet. Some confusion exists concerning nomenclature and identification (superhydrous phase B = phase C; phase D = phase F and phase G)
Current projects
- The 3.65 Å phase
- Stress-induced proton disorder in hydrous ringwoodite
- P-induced phase transition in wadsleyite as a function of „water content“
- Structural phase transitions in lawsonite
- Phase Egg
Contact: S. Jahn, M. Koch-Müller, M. Mrosko, B. Wunder, S. Speziale
Partners:
Mark Welch, The Natural History Museum, London, United Kingdom
Eugen Libowitzky, Institut für Mineralogie und Kristallographie, Universität Wien-Geozentrum, Wien, Austria
Ullrich Schade, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany