Upper Mantle transition elements

The solid crust and the upper mantle make up the region called the lithosphere. Oxygen is the most abundant element in the lithosphere. Unlike the hydrosphere and the atmosphere, the lithosphere contains a large variety of other elements, including deposits of alkali, alkahne earth, and transition metal elements. Table 26-3 lists the most abundant elements in the continental crust portion of the hthosphere. With the exception of gold, platinum, and a few other rare metals that are found free in nature, most metallic elements occur as compounds in minerals. A mineral is a solid, inorganic compound found in nature. Minerals have distinct crystalhne structures and chemical compositions. Most are combinations of metals and nonmetals. 

The model also assumes an incompatible trace element-rich lower mantle and a depleted upper mantle. Bercovici and Kurato (2003) propose that when deep mantle material rises the mineral wadsleyite transforms to olivine (Fig. 3.1), releasing water. The liberated water triggers melting in the transition zone to produce a melt which is rich in water and incompatible trace elements. This melt layer, which is recycled in either a solid or molten state in the transition zone, acts as a chemical filter to... 

Frost, D.J. (2008) The upper mantle and transition zone. Elements, 4,171 176. 

The solid part of Earth s crust and the upper mantle is called the lithosphere, the water found in and on Earth s surface and in the atmosphere is called the hydrosphere, and the gaseous envelope around Earth is called the atmosphere. Oxygen is the most abundant element in the lithosphere however, the lithosphere also contains alkali, alkaline earth, and transition metals. 

Figure 9 Examples of models proposed for the chemical structure of the terrestrial mantle, (a) Whole mantle convection with depletion of the entire mantle. Some subducted slabs pass through the transition zone to the coremantle boundary. Plumes arise from both the core-mantle boundary and the transition zone. This model is not in agreement with isotopic and chemical mass balances, (b) Two-layer mantle convection, with the depleted mantle above the 660 km transition zone and the lower mantle retaining a primitive composition, (c) Blob model mantle where regions of more primitive mantle are preserved within a variously depleted and enriched lower mantle, (d) Chemically layered mantle with lower third above the core comprising a heterogeneous mixture of enriched (mafic slabs) and more primitive mantle components, and the upper two-thirds of the mantle is depleted in incompatible elements (see text) (after Albarede and van der Hilst, 1999).

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