Crustal Manifestations of a Hot Transient Pulse Beneath the Mid-Atlantic Ridge near 60°N

Parnell-Turner, R. E. and White, N. J. and Maclennan, J. and Henstock, T. J. and Murton, B. J. and Jones, S. M. (2013) Crustal Manifestations of a Hot Transient Pulse Beneath the Mid-Atlantic Ridge near 60°N. Earth and Planetary Science Letters, 363. pp. 109-120. ISSN 0012-821X DOI 10.1016/j.epsl.2012.12.030

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Official URL: http://dx.doi.org/10.1016/j.epsl.2012.12.030

Abstract

Since its inception at 62 Ma, mantle convective upwelling beneath Iceland has had a significant influence on Cenozoic vertical motions, magmatism and paleoceanography in the North Atlantic Ocean. Crucially, intersection of the Reykjanes Ridge with the Icelandic Plume provides us with a useful window into the transient activity of this plume. Here, the spreading ridge acts as a linear sampler of plume activity, which is recorded as a series of time-transgressive V-shaped ridges and troughs. We present the results of a detailed study of the spreading ridge close to 60°N, where the youngest V-shaped ridge of thickened oceanic crust is forming today. A combination of multibeam bathymetry and seismic reflection profiles, acquired along and across the ridge axis, is used to map the detailed pattern of volcanism and normal faulting. Along the ridge axis, the density of volcanic seamounts varies markedly, increasing by a factor of two between 59°N and 62°N. Within this zone, seismic imaging shows that there is enhanced acoustic scattering at the seabed. These observations are accompanied by a decrease in mean fault length from View the MathML source to View the MathML source. A 1960–2009 catalog of relocated teleseismic earthquake hypocenters indicates that there is a pronounced gap in seismicity between 59°N and 62°N where the cumulative moment release is two orders of magnitude smaller than that along adjacent ridge segments. A steady-state thermal model is used to show that a combination of increased melt generation and decreased hydrothermal circulation accounts for this suite of observations. The predicted decrease in the thickness of the brittle seismogenic layer is consistent with geochemical modeling of dredged basaltic samples, which require hotter asthenospheric material beneath the spreading axis. Thus, along-axis variation in melt supply caused by passage of a pulse of hot material modulates crustal accretion processes and rheological properties.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA64;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 363
Page Range: pp. 109-120
Identification Number: 10.1016/j.epsl.2012.12.030
Depositing User: Sarah Humbert
Date Deposited: 20 Dec 2012 14:21
Last Modified: 23 Jul 2013 10:05
URI: http://eprints.esc.cam.ac.uk/id/eprint/2639

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