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). 

Fig.: 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)


Prof. Dr. Monika Koch-Müller

Dr. Bernd Wunder

Dr. Sergio Speziale


Mainak Mookherjee, Florida State University, Tallahassee

Mark David Welch, The Natural History Museum, London

Eugen Libowitzky, Universität Wien

Ulrich Schade, Helmholtz Zentrum Berlin, Institut Methoden der Materialentwicklung