Article ID Journal Published Year Pages File Type
4678735 Earth and Planetary Science Letters 2009 10 Pages PDF
Abstract

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 (KAlSi3O8) 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.

Related Topics
Physical Sciences and Engineering Earth and Planetary Sciences Earth and Planetary Sciences (General)
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