Mantle mineralogy

There are a number of trace elements commonly described as incompatible because their partition coefficients (for typical mantle mineralogy) are low, often as low as 10 2 or 10 or less. Prominent examples are K, Rb, U, Th, and the rare earth metals. The principal reason for their incompatibility is evidently their large ionic radii. Concentrations of these elements in mantle-derived rocks are relatively low, and the generalization emerges that they have been expelled from the mantle (at least the upper mantle) and concentrated in the crust, especially continental crust. 

Bina C. R. (1998b) Lower mantle mineralogy and the geophysical perspective. Rev. Mineral. 37, 205-239. 

Pel Y. and Bertka C. M. (1999) Phase transitions in the Earth s mantle and mantle mineralogy. In Mantle Petrology Field Observations and High-pressure Experimentation a Tribute to Francis R. (Joe) Boyd (eds. Y. Fei, M. Bertka Constance, and O. Mysen Bjorn). Geochemical Society, Houston, vol. 6, pp. 189-207. 

Bina C. R. (1998) Lower mantle mineralogy and the geophysical perspective. In Ultrahigh-Pressure Mineralogy Physics and Chemistry of the Earth s Deep Interior (ed. R. J. Hemley). Mineralogical Society of America, Washington, DC, vol. 37, pp. 205-240. 

Stolz A. J. (1987) Fluid activity in the lower emst and upper mantle mineralogical evidence bearing on the origin of amphibole and scapohte in ultramafic and mafic granuhte xenohths. Min. Mag. 51, 719-732. 

Hatch, D.M., Ghose, S. (1989) Symmetiy analysis of the phase transition and twinning in MgSiOs garnet Imphcations for mantle mineralogy. Am Mineral 74 1221-1224 Hazen, R.M., Navrotsky, A. (1996) Effects of pressure on order-disorder reations. Am Mineral 81 1021-1035... 

Determination of crystal structure or unit cell volume in isolation of other physical property measurements is the routine practice in much of solid state research under both ambient and non-ambient conditions. This is often necessitated because the cell assemblies required for property measurements are not compatible with X-ray beams typically available in the laboratory. Centralized facilities, such as are available at the synchrotron, provide a cost-effective environment and opportunity to do more definitive experiments. One recent example from the Stony Brook laboratories will suffice to demonstrate what will become, I believe, the normal mode of operation for the study of important phase transitions in the future. For the study of mantle mineralogy, simultaneous measurements of elastic properties, structure and pressure is now established in large volume devices, (Chen et al. 1999) and being established in DACs as well... 

Of particular significance are the density increases which take place at the upper and lower boundaries of the mantle transition zone, at the 410 km and 660 km discontinuities. In the past it has been argued that the large density increase which takes place at 660 km depth reflects a change in the bulk composition of the mantle with depth. However, the present consensus is that the contrasts can be accommodated simply by phase changes in the mantle mineralogy. (This debate has huge consequences for whether or not the mantle is chemically layered, and is an important factor in the current debate about the nature of mantle convection). 

In detail there are degrees of compatibilty and incompatibility and trace elements win vary in their behaviour in melts of a different composition. For example, P is incompatible in a mantle mineralogy and during partial melting will be quickly concentrated in the melt. In granites, however, even though P is present as a trace element, it is compatible because it is accommodated in the structure of the minor phase apatite. 

Zhang, H. (1993) A study of lower mantle mineralogy by ah initio potential methods, PhD thesis. University of California at Berkeley. 

Hazen, R.M. Rnger, L.W. (1978). Crystal Chemistry of Silicon - Oxygen Bonds at High Pressure Implications for the Earth s Mantle Mineralogy. Science 201, N4361,1122-1123. 

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