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Lithospheric structure of the Gorringe Bank: Insights into its origin and tectonic evolution

AuthorsJimenez-Munt, Ivone ; Fernandez, Manel ; Vergés, Jaume ; Afonso, Juan Carlos ; García-Castellanos, Daniel ; Fullea, J.
KeywordsPotential fields
Serpentinized peridotites
Issue DateOct-2010
PublisherAmerican Geophysical Union
CitationTectonics (29) : TC5019 (2010)
AbstractThe Gorringe Bank is a 5000 m high seamount near the Atlantic coast of Iberia characterized by a 9 m high geoid anomaly and a ~120 mGal Bouguer anomaly relative to the surrounding abyssal plains. It has been linked to a NW directed thrust carrying exhumed upper mantle rocks and transitional crust on top of flexed-down Eurasian oceanic crust along the Tagus Abyssal Plain. However, estimations of crustal shortening have yielded dissimilar results, and the deep structure of the ridge remains highly unknown. We present a restored cross section and a new model of the lithospheric structure based on gravity, geoid, elevation, and the presence of serpentinized peridotites. At least 20 km of shortening took place along a flat-ramp-flat thrust fault, and the density structure of the lithosphere is consistent with mantle serpentinization varying from 70% at the surface to 20% at 14 km depth and 0% at 40 km. The topographic relief and gravity anomalies are explained by assuming a flexural isostatic model with an elastic thickness Te of ~30 km. The evolution of the Gorringe Bank since the Late Jurassic is interpreted in relation to Eurasia-Africa-North America plate motion in four stages: (1) transtension between Newfoundland-Iberia and Africa, which generated small oceanic basins and mantle exhumation; (2) opening of the North Atlantic and seafloor spreading at the NW side of the exhumed Gorringe, which produced gabbro intrusions and serpentinization; (3) a quiescent tectonic period dominated by subsidence and sediment accumulation; and (4) a transpressional plate boundary between Eurasia and Africa with NW directed subcrustal thrusting and generation of the present Gorringe relief.
Publisher version (URL)http://www.agu.org/journals/tc/tc1005/2009TC002458/
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