Sowerby, John Richard; (1997) Electronic absorption spectra of mantle minerals. Doctoral thesis (Ph.D), UCL (University College London).

Preview

Text Electronic_absorption_spectra_.pdf Download (14MB) | Preview

Abstract

Many of the geophysical and crystal chemical properties of the Earth rely on the behaviour of the minerals found in the mantle. This is modified by the presence of small amounts of iron in the lattice of the minerals, and this controls such properties as radiative heat transfer, electrical conductivity and the relative stability of phases. The presence of iron can easily be investigated using electronic absorption spectroscopy, a powerful technique relying on the interaction of light with the electrons of the 3d shell as governed by crystal and ligand field theories. It is this technique that is applied in this thesis. The interactions between the 3d electrons and light are detected as absorption peaks present in the near ultraviolet - visible - near infrared regions. The numbers and positions of these peaks can then be used to obtain information on the local site symmetry around the cation, as well as providing information on charge transfer process between cations and cation and anions. The information provided by the spectra can then be applied to the study of the geophysics and crystal chemistry of the Earth's interior. As the radiative transfer of heat through a phase is governed by the opacity of that phase, the positions of the absorption peaks relative to the peak of the black body radiation curve will determine the opacity. The presence and position of absorption peaks attributed to charge transfer processes can provide information on electrical conduction mechanisms at various depths in the Earth. Finally, the relative stability of iron containing magnesium silicates can be investigated in terms of the crystal field stabilisation energy, obtained from the spectra. Presented here are the results of studies on three minerals, clinoferrosilite. wadsleyite and ferropericlase. These results are than combined with results obtained by other workers in order to draw some conclusions on the geophysical and crystal chemical behaviour of the mantles of the Earth, Mars, and Venus.

Download activity - last month

Export as JSONCSVXML

Download activity - last 12 months

Export as XMLCSVJSON

Downloads by country - last 12 months

Export as JSONCSVXML

Archive Staff Only

View Item