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Polymorphic nature of iron and degree of lattice preferred orientation beneath the Earth's inner core boundary

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Mattesini, Maurizio and Belonoshko, Anatoly B. and Tkalcic, Hrvoje (2018) Polymorphic nature of iron and degree of lattice preferred orientation beneath the Earth's inner core boundary. Geochemistry geophysics geosystems, 19 (1). pp. 292-304. ISSN 1525-2027

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Official URL: http://dx.doi.org/10.1002/2017GC007285




Abstract

Deciphering the polymorphic nature and the degree of iron lattice-preferred orientation in the Earth's inner core holds a key to understanding the present status and evolution of the inner core. A multiphase lattice-preferred orientation pattern is obtained for the top 350 km of the inner core by means of the ab initio based Candy Wrapper Velocity Model coupled to a Monte Carlo phase discrimination scheme. The achieved geographic distribution of lattice alignment is characterized by two regions of freezing, namely within South America and the Western Central Pacific, that exhibit an uncommon high degree of lattice orientation. In contrast, widespread regions of melting of relatively weak lattice ordering permeate the rest of the inner core. The obtained multiphase lattice-preferred orientation pattern is in line with mantle-constrained geodynamo simulations and allows to setup an ad hoc mineral physics scenario for the complex Earth's inner core. It is found that the cubic phase of iron is the dominating iron polymorph in the outermost part of the inner core.


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©2018 Amer Geophysical Union
Maurizio Mattesini acknowledges financial support by the Spanish Ministry of Economy, Industry and Competitiveness (CGL2013-41860-P and CGL2017-86070-R), and by the BBVA Foundation under the "I convocatoria de Ayudas Fundacion BBVA a Investigadores, Innovadores y Creadores Culturales" (PR14 CMA10). A.B.B. was supported by the Swedish Scientific Council (grant 2017-03744 Physics of the Earth's Core). There are no new seismic data in this publication.

Uncontrolled Keywords:Travel-time data; Seismic anisotropy; Elastic-anisotropy; Lowermost mantle; Maxwell stresses; Laboratory model; Lopsided growth; Heterogeneity; Constraints; Attenuation; Earth's inner core; Lattice-preferred orientation; Iron polymorphs
Subjects:Sciences > Physics > Geophysics
Sciences > Physics > Meteorology
ID Code:47225
Deposited On:19 Apr 2018 13:53
Last Modified:01 Jul 2018 23:01

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