Show simple item record

dc.contributor.authorBerry, A.
dc.contributor.authorWalker, A.
dc.contributor.authorHerman, J.
dc.contributor.authorO'Neil, H.
dc.contributor.authorForan, G.
dc.contributor.authorGale, Julian
dc.identifier.citationBerry, Andrew and Walker, Andrew and Hermann, Jorg and O'Neil, Hugh and Foran, Garry and Gale, Julian. 2007. Titanium substitution mechanisms in forsterite. Chemical Geology 242 (1-2): 176-186.

Ti K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra, together with atomic scale calculations, indicate that Ti occupies the Si site in anhydrous forsterite. The energy and intensity of the 1s .3d transition in the XANES spectrum is diagnostic of Ti on a four-coordinate site. The EXAFS spectra determine a Ti-O bond length of 1.81 0.01 This value is in excellent agreement with that of 1.8 A determined computationally by periodic density functional theory and an embedded cluster approach for Ti on the Si site; the calculated bond length for Ti on a Mg site is 2.0 Both computational methods further find that the direct substitution of Ti for Si is energetically favoured relative to substitution of Ti for Mg, charge balanced by either a Mg vacancy or Mg on a Si site. Together the results provide unambiguous evidence for Ti occupying the Si site in anhydrous forsterite. Ti-bearing olivine synthesised at upper mantle conditions in the presence of water, however, exhibits a pre-edge feature corresponding to six-fold coordination. This is consistent with the identification of a Ti-clinohumite-like point defect in samples of olivine from upper-mantle spinel peridotite. The change in Ti site thus provides a mechanism for the incorporation of water in olivine. The total Ti content of olivine will comprise varying contributions from Mg2 [4]TiO4 and Ti-clinohumite-like Mg[6]TiO2(OH)2 substitutions.

dc.publisherElsevier Science BV
dc.subjecthydrous defects
dc.subjectNominally anhydrous minerals
dc.subjectDensity functional theory
dc.titleTitanium substitution mechanisms in forsterite
dc.typeJournal Article
dcterms.source.titleChemical Geology

Berry, Andrew and Walker, Andrew and Hermann, Jorg and O'Neil, Hugh and Foran, Garry and Gale, Julian (2007) Titanium substitution mechanisms in forsterite, Chemical Geology 242(1-2):176-186.


Copyright 2007 Elsevier B.V. All Rights Reserved.

curtin.accessStatusFulltext not available
curtin.facultyDepartment of Applied Chemistry
curtin.facultyDivision of Engineering, Science and Computing
curtin.facultyFaculty of Science

Files in this item


This item appears in the following Collection(s)

Show simple item record