Tectonic history of the Earth’s inner core preserved in its seismic structure

Renaud Deguen; Philippe Cardin

doi:10.1038/ngeo522

Tectonic history of the Earth’s inner core preserved in its seismic structure

Nature Geoscience ◽

10.1038/ngeo522 ◽

2009 ◽

Vol 2 (6) ◽

pp. 419-422 ◽

Cited By ~ 35

Author(s):

Renaud Deguen ◽

Philippe Cardin

Keyword(s):

Inner Core ◽

Seismic Structure ◽

Tectonic History ◽

History Of ◽

Earth’S Inner Core

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On the nature of the crust in the vicinity of the southeast Newfoundland Ridge

Canadian Journal of Earth Sciences ◽

10.1139/e78-152 ◽

1978 ◽

Vol 15 (9) ◽

pp. 1462-1471 ◽

Cited By ~ 22

Author(s):

K. D. Sullivan ◽

C. E. Keen

Keyword(s):

Focal Point ◽

Magnetic Data ◽

Seismic Structure ◽

Grand Banks ◽

The North ◽

Tectonic History ◽

History Of ◽

Continental Origin ◽

Magnetic Lineations ◽

Gravity And Magnetic Data

This paper presents new seismic reflection, refraction, gravity, and magnetic data bearing on the nature of the crust in the vicinity of the Newfoundland Ridge and the J-anomaly Ridge, immediately south of the Grand Banks. This area experienced a complicated plate tectonic history being the focal point for interactions of the North American, African, and Iberian plates. New data have recently been published for this region and conflicting interpretations have been offered in relation to the oceanic or continental origin of the crust there. The data presented here show that the seismic structure and the most reasonable models for the magnetic anomalies are more consistent with an oceanic origin. The trends and offsets in the magnetic lineations and possible differences in subsidence, north and south of the Newfoundland Ridge, are discussed in relation to possible modes of formation of this feature. It is proposed that similar subsidence histories since mid-Cretaceous time on the Grand Banks and J-anomaly Ridge are related to a similarity in the thermal history of the lithosphere beneath these areas, as the ridge crest migrated eastwards, and do not require the same type of crust to underlie both areas.

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Dynamic history of the inner core constrained by seismic anisotropy

10.21203/rs.3.rs-87174/v1 ◽

2021 ◽

Author(s):

Daniel Frost ◽

Marine Lasbleis ◽

Brian Chandler ◽

Barbara Romanowicz

Keyword(s):

Seismic Anisotropy ◽

Inner Core ◽

Rotation Axis ◽

Growth Models ◽

Outer Core ◽

Body Waves ◽

Growth History ◽

History Of ◽

Earth’S Inner Core ◽

Inner Core Growth

Abstract Progressive crystallisation of Earth's inner core over geological times drives convection in the outer core and the generation of the Earth’s magnetic field. Resolving the rate and pattern of inner core growth is thus crucial to understanding the evolution of the geodynamo. The growth history of Earth’s inner core is likely recorded in the distribution and strength of seismic anisotropy arising from deformation texturing constrained by boundary conditions at the inner-core solid-fluid boundary. Travel times of seismic body waves indicate that seismic anisotropy increases with depth. Here we find that the strongest anisotropy is offset from Earth's rotation axis. Using geodynamic growth models and mineral physics calculations, we simulate the development of inner core anisotropy in a self-consistent manner. We show for the first time that an inner core model composed of hexagonally close-packed iron-nickel alloy, deformed by a combination of preferential equatorial growth and slow translation can match the seismic observations without requiring the introduction of hemispheres with sharp boundaries. We find a model of the inner core growth history compatible with external constraints from outer core dynamics, supporting arguments for a relatively young inner core (~0.5-1.5 Ga) and a viscosity >1018 Pa-s.

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