Skelton, R and Walker, AM orcid.org/0000-0003-3121-3255 (2017) Ab initio crystal structure and elasticity of tuite, γ-Ca₃(PO₄)₂, with implications for trace element partitioning in the lower mantle. Contributions to Mineralogy and Petrology, 172. 87. ISSN 0010-7999
Abstract
Tuite forms by the breakdown of apatite at high pressure and is thus expected to play a role in extending the phosphorus cycle beyond the stability field of apatite and into the lower mantle. With its large, high-coordination cation sites, tuite is thought to be able to dissolve large quantities of incompatible elements such as rare earth elements, Sr, Th, and U, and is potentially an important mantle reservoir for these elements. In this paper, ab initio calculations of the structure and elasticity of tuite to lower mantle pressure are presented and used to probe trace element incorporation. The calculated zero-pressure volumes of the M1 and M2 cation sites were 50.23 and 36.61 ų, while the corresponding bulk moduli Kₒ are 116.1 and 94.2 GPa, significantly lower than the 234.1 GPa calculated for the M site of CaSiO₃ perovskite (cpv), another likely host for incompatible elements in the mantle. The partitioning of impurities between tuite and cpv is investigated using a lattice strain model, parameterized by the ab initio calculations, to calculate isovalent substitution energies across a range of pressures and impurity sizes. Additionally, energies of strontium and barium defects in tuite are compared with those of equivalent defects in cpv, and it is found that both elements will partition strongly from cpv into tuite.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | (c) 2017, Springer-Verlag GmbH Germany. This is an author produced version of a paper published in Contributions to Mineralogy and Petrology. Uploaded in accordance with the publisher's self-archiving policy. The final publication is available at Springer via https://doi.org/10.1007/s00410-017-1406-5 |
Keywords: | Tuite; γ-Ca3(PO4)2; Phosphates; Elasticity; Incompatible elements |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/K008803/1 NERC (Natural Environment Research Council) NE/M000044/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 23 Oct 2017 14:16 |
Last Modified: | 28 Jun 2020 05:15 |
Status: | Published |
Identification Number: | 10.1007/s00410-017-1406-5 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:122948 |