Award Abstract #0454700
Collaborative Research: Testing models of magmatic and hydrothermal segmentation: A 3-D seismic tomography experiment at the Endeavour Ridge

NSF Org:	OCE Division of Ocean Sciences
Initial Amendment Date:	May 17, 2006
Latest Amendment Date:	June 3, 2008
Award Number:	0454700
Award Instrument:	Continuing grant
Program Manager:	Brian Midson OCE Division of Ocean Sciences GEO Directorate for Geosciences
Start Date:	August 1, 2006
Expires:	July 31, 2009 (Estimated)
Awarded Amount to Date:	$346728
Investigator(s):	William Wilcock wilcock@u.washington.edu (Principal Investigator) Andrew Barclay (Former Co-Principal Investigator)
Sponsor:	University of Washington 4333 Brooklyn Ave NE SEATTLE, WA 98195 206/543-4043
NSF Program(s):	MARINE GEOLOGY AND GEOPHYSICS
Field Application(s):	0204000 Oceanography
Program Reference Code(s):	OTHR,1620,0000
Program Element Code(s):	1620

ABSTRACT

Competing models for controls on the segmentation and intensity of ridge crest processes are at odds on the scale of mantle and crustal magmatic segmentation, the distribution of hydrothermal venting with respect to a volcanic segment and the properties of the thermal boundary layer that transports energy between the magmatic and hydrothermal systems. The recent discovery of an axial magma chamber (AMC) reflector beneath the Endeavour segment of the Juan de Fuca ridge, as well as systematic along axis changes in seafloor depth, ridge crest morphology and hydrothermal venting provide an ideal target for testing conflicting hypotheses. The scientific objectives of this project are to: (1) Determine if the segmentation and intensity of the magma-hydrothermal systems at the Endeavour ridge are related to magma supply or to the magma plumbing between the mantle and crust, and (2) Constrain the thermal and magmatic structure underlying the Endeavour hydrothermal system in order to understand the patterns of energy transfer. An active source seismic tomography experiment, using an array of 64 three-component ocean-bottom seismometers, will image the 3-D seismic structure of the crust and topmost mantle along an 80-km-long section of the Endeavour ridge. The experiment will image four targets: (1) crustal thickness variations within 25 km of the axial high (0 to 900 kyr); (2) the 2-D (i.e., map view) structure of the uppermost mantle beneath the spreading axis; (3) the 3-D structure of the crustal magmatic system and (4) the detailed 3-D, shallow crustal thermal structure beneath the Endeavour vent field. The results of imaging will define the recent history of magma supply, the pattern of melt delivery from the mantle to the crust and the structure and segmentation of the subseafloor magmatic and hydrothermal systems. These measurements are essential to testing critically competing hypotheses for what regulates the intensity of ridge crest magmatic and hydrothermal processes.

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