Phase transitions and mineralogy of the upper mantle

The Earth's upper mantle extends from below the crust to a depth of about 410 km. Here, we review the mineralogical and chemical composition of the upper mantle, especially with respect to the observed heterogeneities, both found in natural mantle rocks and in experiments. We focus on subsolidus phase transitions determined using experimental techniques. Although most upper mantle rocks can be assumed to be peridotite mostly made of olivine and pyroxene, other minerals, including oxides and hydrates, should be taken into account, especially when they participate in transitions or chemical reactions that may affect the physical properties of the mantle rocks.