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GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,
VOL. 8,
Q09009,
doi:10.1029/2007GC001673,
2007
Trench-parallel fluid flow in subduction zones resulting from temperature differences
Glenn A. Spinelli
Earth and Environmental Science Department, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801
USA
Demian M. Saffer
Department of Geosciences, Pennsylvania State University, Deike Building, University Park, PA 16802 USA
Abstract
Differences in the thermal state of subducting crust along the trench of a subduction zone cause differences in subduction
zone temperature that persist to tens of kilometers down-dip of the trench. The resulting differences in fluid viscosity,
permeability, and hydraulic conductivity can lead to trench-parallel variations in fluid pressure on the plate boundary fault.
Temperature differences in locations with low décollement temperature (<75°C) at the trench result in large differences in
fluid viscosity and fluid flow from the cold to the hot side of the system. Margins characterized by high décollement temperature
at the trench are probably dominated by temperature-controlled differences in intrinsic permeability, resulting in fluid flow
from the hot to the cold side of the system. Margins with large trench-parallel temperature differences support considerable
trench-parallel fluid flow, and the effect is accentuated for cases where compaction driven dewatering is concentrated near
the trench. Type locations for along-strike hydrologic differences include margins with subducting crust with differences
in plate age along the trench or patchy hydrothermal circulation. In such cases, the three-dimensional pattern of subduction
zone fluid flow should be considered when inferring the location of the source of fluids sampled from boreholes or seeps.
Additionally, trench-parallel differences in fluid pressure control effective stress on the plate boundary fault. Reduced
effective stress on the plate boundary on the low hydraulic conductivity side of a subduction zone reduces the effective friction
coefficient, which both reduces frictional heating and may delay the onset of frictional instability.
Received 2
May
2007;
accepted 7
August
2007;
published 19
September
2007.
Keywords: subduction;
temperature;
pressure;
décollement.
Index Terms: 3021 Marine Geology and Geophysics: Marine hydrogeology; 3060 Marine Geology and Geophysics: Subduction zone processes (1031, 3613, 8170, 8413); 0545 Computational Geophysics: Modeling (4255).
Read Full Article (file size: 905027 bytes) Cited by
Citation: Spinelli, G. A., and D. M. Saffer
(2007),
Trench-parallel fluid flow in subduction zones resulting from temperature differences,
Geochem. Geophys. Geosyst.,
8,
Q09009,
doi:10.1029/2007GC001673.
Copyright 2007 by the American Geophysical Union.
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