Magmatic focusing to mid‐ocean ridges: the role of grain‐size variability and non‐Newtonian viscosity
Magmatic focusing to mid‐ocean ridges: the role of grain‐size variability and non‐Newtonian viscosity
Melting beneath mid-ocean ridges occurs over a region that is much broader than the zone of magmatic emplacement that forms the oceanic crust. Magma is focused into this zone by lateral transport. This focusing has typically been explained by dynamic pressure gradients associated with corner flow, or by a sublithospheric channel sloping upward toward the ridge axis. Here we discuss a novel mechanism for magmatic focusing: lateral transport driven by gradients in compaction pressure within the asthenosphere. These gradients arise from the covariation of melting rate and compaction viscosity. The compaction viscosity, in previous models, was given as a function of melt fraction and temperature. In contrast, we show that the viscosity variations relevant to melt focusing arise from grain-size variability and non-Newtonian creep. The asthenospheric distribution of melt fraction predicted by our models provides an improved explanation of the electrical resistivity structure beneath one location on the East Pacific Rise. More generally, we find that although grain-size and non-Newtonian viscosity are properties of the solid phase, their effect on melt transport beneath mid-ocean ridges is more profound than their effect on the mantle corner flow.
4342-4355
Turner, Andrew J.
d590ba07-07c3-4097-a2ab-09a26f2001b9
Katz, Richard F.
01d7145d-41ad-44eb-9671-ac78313e82c2
Behn, Mark D.
72f91c79-aea0-4a4f-879e-3813696b3eb2
Keller, Tobias
d8dfcfa5-89d1-4203-aa2d-8c142c00a169
17 January 2018
Turner, Andrew J.
d590ba07-07c3-4097-a2ab-09a26f2001b9
Katz, Richard F.
01d7145d-41ad-44eb-9671-ac78313e82c2
Behn, Mark D.
72f91c79-aea0-4a4f-879e-3813696b3eb2
Keller, Tobias
d8dfcfa5-89d1-4203-aa2d-8c142c00a169
Turner, Andrew J., Katz, Richard F., Behn, Mark D. and Keller, Tobias
(2018)
Magmatic focusing to mid‐ocean ridges: the role of grain‐size variability and non‐Newtonian viscosity.
Geochemistry, Geophysics, Geosystems, 18 (12), .
(doi:10.1002/2017GC007048).
Abstract
Melting beneath mid-ocean ridges occurs over a region that is much broader than the zone of magmatic emplacement that forms the oceanic crust. Magma is focused into this zone by lateral transport. This focusing has typically been explained by dynamic pressure gradients associated with corner flow, or by a sublithospheric channel sloping upward toward the ridge axis. Here we discuss a novel mechanism for magmatic focusing: lateral transport driven by gradients in compaction pressure within the asthenosphere. These gradients arise from the covariation of melting rate and compaction viscosity. The compaction viscosity, in previous models, was given as a function of melt fraction and temperature. In contrast, we show that the viscosity variations relevant to melt focusing arise from grain-size variability and non-Newtonian creep. The asthenospheric distribution of melt fraction predicted by our models provides an improved explanation of the electrical resistivity structure beneath one location on the East Pacific Rise. More generally, we find that although grain-size and non-Newtonian viscosity are properties of the solid phase, their effect on melt transport beneath mid-ocean ridges is more profound than their effect on the mantle corner flow.
This record has no associated files available for download.
More information
Accepted/In Press date: 15 November 2017
e-pub ahead of print date: 6 December 2017
Published date: 17 January 2018
Identifiers
Local EPrints ID: 488266
URI: http://eprints.soton.ac.uk/id/eprint/488266
ISSN: 1525-2027
PURE UUID: 108fdf65-9813-4491-96ea-fb024126c26b
Catalogue record
Date deposited: 19 Mar 2024 17:48
Last modified: 21 Mar 2024 03:16
Export record
Altmetrics
Contributors
Author:
Andrew J. Turner
Author:
Richard F. Katz
Author:
Mark D. Behn
Author:
Tobias Keller
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics