The plastic deformation of iron at pressures of the Earth's inner core

Citation
Hr. Wenk et al., The plastic deformation of iron at pressures of the Earth's inner core, NATURE, 405(6790), 2000, pp. 1044-1047
Citations number
30
Categorie Soggetti
Multidisciplinary,Multidisciplinary,Multidisciplinary
Journal title
NATURE
ISSN journal
00280836 → ACNP
Volume
405
Issue
6790
Year of publication
2000
Pages
1044 - 1047
Database
ISI
SICI code
0028-0836(20000629)405:6790<1044:TPDOIA>2.0.ZU;2-B
Abstract
Soon after the discovery of seismic anisotropy in the Earth's inner core(1) , it was suggested that crystal alignment attained during deformation might be responsible(2). Since then, several other mechanisms have been proposed to account for the observed anisotropy(3,4), but the lack of deformation e xperiments performed at the extreme pressure conditions corresponding to th e solid inner core has limited our ability to determine which deformation m echanism applies to this region of the Earth(5). Here we determine directly the elastic and plastic deformation mechanism of iron at pressures of the Earth's core, from synchrotron X-ray diffraction measurements of iron, unde r imposed axial stress, in diamond-anvil cells. The epsilon-iron (hexagonal ly close packed) crystals display strong preferred orientation, with c-axes parallel to the axis of the diamond-anvil cell. Polycrystal plasticity the ory predicts an alignment of c-axes parallel to the compression direction a s a result of basal slip, if basal slip is either the primary or a secondar y slip system. The experiments provide direct observations of deformation m echanisms that occur in the Earth's inner core, and introduce a method for investigating, within the laboratory, the rheology of materials at extreme pressures.