V. Trommsdorff Abstract.
All charges exhibit strong chemical zoning.
Fluid, melt and hydrous solids were mostly concentrated at the top, bottom and along the wall of the capsules. In contrast, the centre of the capsule was enriched in SiO 2 . The observed zoning can neither be explained by gravitational settling nor by a thermal gradient alone. If strong chemical zoning is taken into account, the occurrence of more phases than allowed by the phase rule can be explained by separating the bulk into several domains of different bulk compositions.