Heterogeneous distribution of phosphorus in olivine from otherwise well-equilibrated spinel peridotite xenoliths and its implications for the mantle geochemistry of lithium

Mallmann, Guilherme, O'Neill, Hugh St. C. and Klemme, Stephan (2009) Heterogeneous distribution of phosphorus in olivine from otherwise well-equilibrated spinel peridotite xenoliths and its implications for the mantle geochemistry of lithium. Contributions to Mineralogy and Petrology, 158 4: 485-504. doi:10.1007/s00410-009-0393-6


Author Mallmann, Guilherme
O'Neill, Hugh St. C.
Klemme, Stephan
Title Heterogeneous distribution of phosphorus in olivine from otherwise well-equilibrated spinel peridotite xenoliths and its implications for the mantle geochemistry of lithium
Journal name Contributions to Mineralogy and Petrology   Check publisher's open access policy
ISSN 0010-7999
1432-0967
Publication date 2009-01-01
Sub-type Article (original research)
DOI 10.1007/s00410-009-0393-6
Open Access Status
Volume 158
Issue 4
Start page 485
End page 504
Total pages 20
Place of publication Heidelberg, Germany
Publisher Springer
Language eng
Abstract The major- and trace-element abundances of the coexisting phases of four metasomatized spinel peridotite xenoliths from the Anakies locality (SE Australia) were determined by electron microprobe and laser-ablation ICP-MS. The compositions of all phases are remarkably homogeneous, with the exception of phosphorus (P), lithium (Li) and sodium (Na) in olivine. These three elements are enriched in large parts of most olivine crystals due to a second metasomatic episode. Apart from these elements, all phases are in mutual equilibrium with respect to both their major- and trace-element compositions. Li and Na show a strong correlation with P in olivine, although molar Li + Na are an order of magnitude less than molar P, indicating that the substitution mechanism of these elements is more complex than the simple charge-balanced coupled exchange IVSi 4+ + VI(FeMg) 2+ = IVP 5+ + VI(LiNa) +. We suggest that Li and Na are decorating octahedral-site cation vacancies formed by the original incorporation of P. Elemental maps revealed that the P zoning patterns are concentric in a few large olivine porphyroblasts, but form irregular patches in most crystals. This distribution of P is proposed to be the result of a two-stage process, whereby the initial concentric zoning, caused by its exceptionally sluggish diffusion after metasomatic influx, is broken up by extensive sub-solidus deformation and recrystallization, attesting to large grain-scale strains even within the lithosphere. Such strains must be an efficient means of ensuring trace-element equilibrium during partial melting. The association of Li with P in olivine may help to explain the variability of Li abundances in mantle minerals and to interpret Li diffusion experiments and Li isotopic fractionation.
Keyword Coupled substitution
Lithium
Mantle
Olivine
Partitioning
Phosphorous
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Earth Sciences Publications
 
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