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GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,
VOL. 5,
Q12007,
doi:10.1029/2004GC000764,
2004
Tectonic/volcanic segmentation and controls on hydrothermal venting along Earth's fastest seafloor spreading system, EPR 27°–32°S
Richard Hey
School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, Hawaii, 96822, USA
Edward Baker
NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way N.E., Seattle, Washington, 98115-0070, USA
DelWayne Bohnenstiehl
Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York, 10964, USA
Gary Massoth
Institute of Geological and Nuclear Sciences, Ltd., 30 Gracefield Road, Lower Hutt, P.O. Box 31-312, New Zealand
Martin Kleinrock
Joint Oceanographic Institutions, Inc., 1201 New York Ave, NW, Suite 400, Washington, DC, 20005, USA
Fernando Martinez
School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, Hawaii, 96822, USA
David Naar
College of Marine Science, University of South Florida, 140 Seventh Avenue South, St. Petersburg, Florida, 33701-5016, USA
Debra Pardee
School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, Hawaii, 96822, USA
John Lupton
NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive, Newport, Oregon, 97365, USA
Richard Feely
NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way N.E., Seattle, Washington, 98115-0070, USA
Jim Gharib
School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, Hawaii, 96822, USA
Joe Resing
NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way N.E., Seattle, Washington, 98115-0070, USA
Cristian Rodrigo
Servicio Hidrografico y Oceanografico de la Armada de Chile, Errazuriz 232 Playa Ancha, Valparaiso, Chile
Francis Sansone
School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, Hawaii, 96822, USA
Sharon Walker
NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way N.E., Seattle, Washington, 98115-0070, USA
Abstract
We have collected 12 kHz SeaBeam bathymetry and 120 kHz DSL-120 side-scan sonar and bathymetry data to determine the tectonic
and volcanic segmentation along the fastest spreading (∼150 km/Myr) part of the global mid-ocean ridge system, the southern
East Pacific Rise between the Easter and Juan Fernandez microplates. This area is presently reorganizing by large-scale dueling
rift propagation and possible protomicroplate tectonics. Fracture patterns observed in the side-scan data define structural
segmentation scales along these ridge segments. These sometimes, but not always, correlate with linear volcanic systems defining
segmentation in the SeaBeam data. Some of the subsegments behave cohesively, with in-phase tectonic activity, while fundamental
discontinuities occur between other subsegments. We also collected hydrothermal plume data using sensors mounted on the DSL-120
instrument package, as well as CTDO tow-yos, to determine detailed structural and volcanic controls on the hydrothermal vent
pattern observed along 600 km of the Pacific-Nazca axis. Here we report the first rigorous correlation between coregistered
hydrothermal plume and high-resolution marine geophysical data on similar scales and over multisegment distances. Major plume
concentrations were usually found where axial inflation was relatively high and fracture density was relatively low. These
correlations suggest that hydrothermal venting is most active where the apparent magmatic budget is greatest, resulting in
recent eruptions that have paved over the neovolcanic zone. Areas of voluminous acoustically dark young lava flows produced
from recent fissure eruptions correlate with many of the major hydrothermal vent areas. Increased crustal permeability, as
gauged by increased fracture density, does not enhance hydrothermal venting in this area. Axial summit troughs and graben
are rare, probably because of frequent volcanic resurfacing in this superfast spreading environment, and are not good predictors
of hydrothermal activity here. Many of the hydrothermal areas are found in inflated areas near the ends of segments, suggesting
that abundant magma is being supplied to these areas.
Received 25
May
2004;
accepted 21
October
2004;
published 15
December
2004.
Keywords: seafloor spreading;
mid-ocean ridges;
hydrothermal plumes.
Index Terms: 3035 Marine Geology and Geophysics: Midocean ridge processes; 3045 Marine Geology and Geophysics: Seafloor morphology and bottom photography; 3094 Marine Geology and Geophysics: Instruments and techniques; 4832 Oceanography: Biological and Chemical: Hydrothermal systems; 8150 Tectonophysics: Plate boundary—general (3040).
Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 2200009 bytes)
Citation: Hey, R., et al.
(2004),
Tectonic/volcanic segmentation and controls on hydrothermal venting along Earth's fastest seafloor spreading system, EPR 27°–32°S,
Geochem. Geophys. Geosyst.,
5,
Q12007,
doi:10.1029/2004GC000764.
Copyright 2004 by the American Geophysical Union.
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