Tectonic/volcanic segmentation and controls on hydrothermal venting along Earth's fastest seafloor spreading system, EPR 27°

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Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 2200009 bytes) 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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