Extensional tectonics in the Gorringe Bank rocks, Eastern Atlantic ocean: evidence of an oceanic ultra‐slow mantellic accreting centre

Abstract

The Gorringe Bank corresponds to an upper mantle peridotite ridge enclosing a 500‐m thick/ 50‐km long laccolith‐like body of gabbro, locally cut and poorly covered by tholeiitic rocks. Strain and kinematic analysis of orientated gabbros and peridotites sampled during the GORRINGE diving cruise (1996) provides new kinematic constraints on extensional high‐temperature deformation recorded at deep levels during stretching, near an accreting centre axis of a mantle‐dominant oceanic lithosphere. It is argued that the Gorringe Bank lithosphere formed at an oceanic ultra‐slow, N010°–020°‐trending accreting centre, mostly by passive tectonic denudation of the mantle, without any synchronous large magmatism. This peculiar lithosphere may be representative of the Iberia oceanic domain located between the continent and the J anomaly ridge, which likely marks the beginning of true spreading at an oceanic spreading ridge.