Unknown
In:
J. Geophys. Res., San Francisco, Schweizerbart'sche Verlagsbuchhandlung, vol.
110, no. B09410, pp. 205-218, pp. TC1011, (ISSN 0016-8548, ISBN
3-510-50045-8)
Publication Date:
2005
Description:
Theoretical and experimental studies indicate that when oceanic crust is
hotter than about 800 C, variations in crustal thickness drive lower crustal flow. We
investigate the nature of crustal flow beneath Iceland, where zero-age crust varies in
thickness from under 20 km to over 40 km over a distance of 100 km and temperatures
exceed 1000 C below depths of a few kilometers. We model the regional characteristics of
crustal flow using the two-dimensional channel flow equation with depth-dependent
viscosity. The model predicts the observed decay in crustal thickness contrasts between
zero-age and off-axis crust on shore Iceland and development of a sharp Moho step as the
plate moves away from the rift axis. These features become locked in place as plate
cooling increases the viscosity. Observations are best matched by model predictions when
the solidus viscosity is of order 10^18 Pa s, in agreement with viscosity estimates from
deformation rates associated with deglaciation and plate boundary processes. Crustal
flow acts to erase the crustal thickness memory of ridge-plume interaction, so that maps
of Icelandic crustal thickness can be used neither to derive a detailed plume flux
history nor to test in detail whether the Iceland Plume center is fixed relative to
other hot spots. Crustal flow beneath Iceland is an unusually clear example of the kind
of flow postulated to explain continental phenomena including exhumation of metamorphic
core complexes and associated development of low-angle detachments within extensional
terrains and sharp-edged plateau topography in major collisional belts
Keywords:
Rheology
;
Plate tectonics
;
GeodesyY
;
ConvolutionE
;
crustal
;
flow
;
Iceland
;
viscosity
;
8137
;
Tectonophysics:
;
Hotspots,
;
large
;
igneous
;
provinces,
;
and
;
flood
;
basalt
;
volcanism
;
8120
;
Dynamics
;
of
;
lithosphere
;
and
;
mantle:
;
general
;
(1213)
;
3035
;
Marine
;
Geology
;
and
;
Geophysics:
;
Midocean
;
ridge
;
processes
;
8011
;
Structural
;
Geology:
;
Kinematics
;
of
;
crustal
;
and
;
mantle
;
deformation
;
9325
;
Geographic
;
Location:
;
Atlantic
;
Ocean
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