Unknown
In:
J. Geophys. Res., Amsterdam, Schweizerbart'sche Verlagsbuchhandlung, vol. 107,
no. B10, pp. ECV 6-1-ECV 6-17, pp. 2223, (ISSN 0016-8548, ISBN 3-510-50045-8)
Publication Date:
2002
Description:
We use laboratory experiments and numerical models to quantify the effects
of dike interaction on the focusing of magma as it ascends in the upper mantle.
Laboratory experiments involve injecting buoyant fluid into the base of a tank filled
with solidified gelatin. When we initiate two dikes parallel to each other, but
separated by a horizontal distance x, they tend to merge as they ascend. This behavior
is also predicted by numerical models of two-dimensional dikes. The key parameters that
control the maximum horizontal separation x c over which dikes will intersect are dike
driving pressures, dike head lengths L (i.e., the length over which driving pressure is
large), and the difference between the principal stresses of the remote stress field.
When the remote differential stress is small compared to the dike driving pressure, two
dikes of equal driving pressure and length will intersect over distances of x c ? L.
This distance decreases with increasing remote differential stress. We quantify the
effects on magma transport from a broad lateral distribution of magma using numerical
simulations of multiple-dike interaction. When the average dike spacing prior to
interaction is within ?3 L and remote differential stresses are insignificant, dike
interaction can focus magma over horizontal distances many times L but at least ?6 L.
Dike interaction can focus magma in the asthenosphere beneath mid-ocean ridges for low
mantle viscosities (?10 19 Pa s) and if dikes initiate with average separations of a few
hundred meters, or less. Such focusing is predicted to grow dikes of increasing magma
flux approaching lateral separations of a kilometer.
Keywords:
Fluids
;
Plate tectonics
;
ascent
;
sheeted
;
dykes
;
Modelling
;
JGR
;
8434
;
Volcanology:
;
Magma
;
migration
;
8145
;
Tectonophysics:
;
Physics
;
of
;
magma
;
and
;
magma
;
bodies
;
8120
;
Dynamics
;
of
;
lithosphere
;
and
;
mantle--general
;
3035
;
Marine
;
Geology
;
and
;
Geophysics:
;
Midocean
;
ridge
;
processes
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