The Relationship Between Fluids and Tectonics at the Middle America Convergent Margin

HR: 08:35h
AN: T11E-03 [Abstracts]
TI: The Relationship Between Fluids and Tectonics at the Middle America Convergent Margin
AU: Grevemeyer, I
EM: igrevemeyer@ifm-geomar.de
AF: IFM-GEOMAR and SFB574, Wichhofstrasse 1-3, Kiel, 24148 Germany
AU: * Ranero, C
EM: cranero@icm.es
AF: ICREA, Instituto de Ciencias del Mar, CSIC, Pg. de la Barceloneta 37-49, Barcelona, 08003 Spain
AU: Sahling, H
EM: hsahling@uni-bremen.de
AF: Research Center Ocean Margins, University of Bremen, Bremen, 28359 Germany
AU: Barckhausen, U
EM: u.barckhausen@bgr.de
AF: Bundesanstalt f〉 Geowissenschaften and Rohstoffe, Stilleweg 2, Hannover, 30655 Germany
AU: Hensen, C
EM: chensen@ifm-geomar.de
AF: IFM-GEOMAR and SFB574, Wichhofstrasse 1-3, Kiel, 24148 Germany
AU: Wallmann, K
EM: kwallmann@ifm-geomar.de
AF: IFM-GEOMAR and SFB574, Wichhofstrasse 1-3, Kiel, 24148 Germany
AU: Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: IFM-GEOMAR and SFB574, Wichhofstrasse 1-3, Kiel, 24148 Germany
AU: Vannucchi, P
EM: paolavi@geo.unifi.it
AF: Universita` di Firenze, Via La Pira 4, Florence, 50121 Italy
AU: von Huene, R
EM: rhuene@mindspring.com
AF: IFM-GEOMAR and SFB574, Wichhofstrasse 1-3, Kiel, 24148 Germany
AU: McIntosh, K
EM: kirk@utig.ig.utexas.edu
AF: University of Texas at Austin, 4412 Spicewood Springs Rd., Bldg 600, Austin, TX 78759-8500 United States
AB: We have studied the hydrological system and tectonic structure along ~600 km of the Middle America margin (Costa Rica and Nicaragua) integrating thermal structure from heat flux data, seismic reflection images, detection of seafloor seepage sites and analysis of fluids. An inventory of active seepage sites was obtained with a multiscale approach, applying methods with increasing spatial resolution: multibeam bathymetry followed by mapping of selected regions with deep-towed sides-can sonar, and groundtruthing of key structures with 63 deep-towed camera observations. Results were used to plan sampling of material and fluid at vents. Fluid distribution and migration appear the main factors governing the evolution of the margin. Most free water along the plate boundary comes from dehydration of subducting sediment. The thermal structure of the subducting plate determines the area where water chemically-bond in sediment is released. The size of this area corresponds to the width of a subsiding continental slope, with subsidence caused by basal tectonic erosion. Margin collapse involves extensional faulting that promotes upward migration of plate-boundary fluids. As much as 90% of the water provided by minerals in subducting sediment is recycled into the ocean through mid-slope seepage, and only a small volume is transported along the dＤollement towards the deformation front. The thermally controlled decline in water release along the plate boundary implies changes in effective stress and fault mechanics that may be responsible for the onset of seismogenesis.
DE: 3025 Marine seismics (0935, 7294)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 8104 Continental margins: convergent
SC: Tectonophysics [T]
MN: Fall Meeting 2005