Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 288, Issue 3-4, Pages 349-358Publisher
ELSEVIER
DOI: 10.1016/j.epsl.2009.09.037
Keywords
hollandite; elasticity; mantle discontinuity; subduction; crustal materials
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Funding
- European Commission [MRTN-CT-2006-035957]
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Subduction of differentiated continental and oceanic crusts through sediments and basalt to the deep mantle has been shown to be a likely source for the geochemical signature of ocean island basalts that are enriched in large ion lithophile elements such as K, Na, Rb, and Sr. At high pressure such a lithology will consist of stishovite, majorite and hollandite, where hollandite (KAISi(3)O(8)) can readily host the large ion lithophile elements, and is hence a geochemically important phase. Here we study the elasticity of hollandite up to lower mantle pressure by electronic structure simulations and attempt to constrain the volume percent of hollandite in a subduction zone environment. In agreement with experiments we predict a phase transition from a low pressure tetragonal phase to a high pressure monoclinic phase at 33 GPa. The phase transition has significant effects on the elastic properties of hollandite, with an increase in shear modulus of 10%. Based on the computed reflection coefficient across the transition and observed reflectance for mid-mantle seismic scatterers (920 km discontinuity) we constrain the maximum volume of hollandite to be around 5% in a subduction zone environment. (C) 2009 Elsevier B.V. All rights reserved.
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