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

• Published in: Tectonics
• Main Authors: Jiménez-Munt, I., Fernàndez, M., Vergés, J., Afonso, J. C., Garcia-Castellanos, D., Fullea, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: Newfoundland; North Atlantic
• Online Access: https://researchers.mq.edu.au/en/publications/80bc7e15-1d4f-4edc-9ebc-2a90ed9a389a; https://doi.org/10.1029/2009TC002458; https://research-management.mq.edu.au/ws/files/62413161/Publisher%20version%20(open%20access).pdf; http://www.scopus.com/inward/record.url?scp=78149342431&partnerID=8YFLogxK

The 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 T e 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.