HR: 1340h
AN: B13A-0183    [Abstracts]
TI: Evidence for Along-Strike Hydrothermal Circulation Within Young Oceanic Crust on the Eastern Flank of the Endeavour Axis, Juan de Fuca Ridge
AU: * Hutnak, M
EM: mhutnak@es.ucsc.edu
AF: University of California, Santa Cruz, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Fisher, A T
EM: afisher@es.ucsc.edu
AF: University of California, Santa Cruz, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Zuehlsdorff, L
EM: lzuehls@mtu.uni-bremen.de
AF: University of Bremen, Department of Geosciences PO Box 33 04 40, Bremen, 28334 Germany
AU: Spiess, V
EM: vspiess@mtu.uni-bremen.de
AF: University of Bremen, Department of Geosciences PO Box 33 04 40, Bremen, 28334 Germany
AU: Davis, E
EM: edavis@nrcan.gc.ca
AF: Pacific Geoscience Centre, Geological Survey of Canada 9860 W. Saanich Rd., Sidney, BC V8L 4B2 Canada
AB: Many geological, geophysical, and geochemical indicators at spreading centers suggest that the dominant direction of fluid circulation may be along-strike, subparallel to the primary orientation of neovolcanic and near-ridge faulting. Researchers are beginning to identify additional evidence from young ridge flanks for along-strike fluid (and heat and solute) flow. We present newly-compiled thermal, swath-map, and seismic data collected on young crust east of the Endeavour Segment of the Juan de Fuca Ridge. Hydrosweep data reveal several prominent basaltic outcrops just north of the ODP Leg 168 drilling transect, within an area experiencing a hydrothermal transition (HT) from exposed to sediment-covered basement. Seafloor heat flow is strongly suppressed 20 km east of the spreading center, and the pattern of thermal rebound with increasing distance from the ridge has been interpreted as evidence for dominantly across-strike hydrothermal circulation. We show that within one part of the hydrothermal transition, located on 1.2-1.3 Ma seafloor, the data are at least as well explained by along-strike fluid circulation, with cold seawater recharging through outcrops to the north of the HT area. Application of a simple analytical model for coupled heat and fluid flow suggests specific discharge in basement on the order of 1 m/yr, a rate consistent with earlier estimates of across-strike circulation, and with independent estimates of driving forces and crustal permeability. Dominantly along-strike circulation has also been inferred on 3.5 Ma crust to the east of the HT area, suggesting that this mode of fluid transport may be the rule, rather than the exception, on this young ridge flank. Since primary flow paths are likely associated with tectonic processes that occur during and soon after the crust is formed, it seems probable that along-strike fluid flow is also important today at the Endevaour Segment.
DE: 8130 Heat generation and transport
DE: 8135 Hydrothermal systems (8424)
DE: 4832 Hydrothermal systems
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3035 Midocean ridge processes
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting