Structure, crystal chemistry and stability of 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, phase Egg. 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 (e. g., dehydration reactions).  

Current projects: the 3.65 Å phase, lawsonite, phase Egg

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)

Cooperation

Mainak Mookherjee

Florida State University, Tallahassee

Mark David Welch

The Natural History Museum, London

Eugen Libowitzky

Universität Wien

Ulrich Schade

Helmholtz-Zentrum Berlin