Nonlinear stress dependence of permeability; a mechanism for episodic fluid flow in accretionary wedges

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doi: 10.1130/0091-7613(1999)027<0239:NSDOPA>2.3.CO;2
Author(s): Bolton, Alistair J.; Clennell, M. Ben; Maltman, Alex J.
Author Affiliation(s): Primary:
University of Wales, Institute of Geography and Earth Sciences, Aberystwyth, United Kingdom
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 27(3), p.239-242. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 24 refs.; illus.
Summary: Recent studies of the hydrogeology of accretionary wedges demonstrate that permeability is a dynamic property that depends upon the scale of observation and the prevailing stress state during measurement. We present results of laboratory geotechnical tests on sediments cored from the Costa Rica convergent margin during Ocean Drilling Program Leg 170. By measuring the permeability of samples of differing lithology before, during, and after shearing we show that hydrological behavior is linked to the consolidation state of the sediment at the onset of shear, and to the formation or reactivation of deformation fabrics. One sample obtained from a fault zone displayed a high permeability-effective stress dependence after being deformed at a high overconsolidation ratio. Under these conditions, shear zones in fine-grained sediments can dilate and thereby act as efficient fluid-flow conduits. Such stress-dependent permeability typifies the cyclic pressure build-up and release mechanisms (valving) invoked for many tectonic settings. We infer that a fracture permeability, opened up at high fluid pressures, is several times to several orders of magnitude greater than the matrix permeability. Our results help quantify the degree to which hydromechanical coupling can enhance flow in the actively deforming parts of accretionary wedges.
Year of Publication: 1999
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Caribbean Plate; Caribbean region; Central America; Cocos Plate; Consolidation; Cores; Costa Rica; Cycles; Dilatancy; East Pacific; Experimental studies; Fine-grained materials; Fluid dynamics; Fluid pressure; Fracture zones; Laboratory studies; Leg 170; Marine sediments; Mechanical properties; Middle America Trench; Nonlinear materials; North Pacific; Northeast Pacific; ODP Site 1039; ODP Site 1040; ODP Site 1043; Ocean Drilling Program; Overconsolidated materials; Overpressure; Pacific Ocean; Periodicity; Permeability; Plate convergence; Plate tectonics; Pressure; Sediments; Shear; Soil mechanics; Stress
Coordinates: N093823 N093823 W0861200 W0861200
N093943 N093943 W0861045 W0861045
N093916 N093916 W0861109 W0861109
Record ID: 1999024958
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