Seamount,anton,dohrn and the evolution of the rockall trough

• Main Authors: Jones, Ejw, Siddall, R, Thirlwall, Mf, Chroston, Pn, Lloyd, Aj
• Format: Article in Journal/Newspaper
• Language: English
• Published: Gauthier-Villars 1994
• Subjects: ATLANTIC; BASALTS; GUYOT; RIFTING; ROCKALL; Anton Dohrn Seamount; Rockall Trough; Iceland
• Online Access: https://archimer.ifremer.fr/doc/00098/20887/18501.pdf; https://archimer.ifremer.fr/doc/00098/20887/

Seismic data from the flat-topped Anton Dohrn Seamount in the central Rockall Trough reveal that the feature is capped by a thin (approximately 100 m) sedimentary layer which covers an extensive erosion surface lying approximately 800 m below sea level. The surface of erosion truncates a volcanic sequence that outcrops on the eastern side of the seamount to form a well-defined terrace from which alkali basalts and chalks of late Cretaceous age have been recovered. A refraction profile shot over the summit plateau and ultrasonic measurements on the basalts suggest that sedimentary and volcanoclastic units are abundant constituents of a low-velocity (3.69 km s-1) volcanic core which persists to depths of over 1 500 m. The seamount differs from the shallow Cenozoic volcanic piles in the region where high seismic velocities (> 5 km s-1) occur close to the sea bed. Minor element abundances and REE inversion indicate that the Anton Dohrn basalts have been generated as a result of within-plate igneous activity, with most melting taking place in the spinel-garnet peridotite transition zone. Pb-isotope ratios are consistent with eruption of the basalts in an oceanic rift. There is no evidence for contamination by continental crust. The presence of late Cretaceous sediments, the REE patterns and Nd- and Pb-isotope ratios suggest that the seamount is related to a distinct phase of igneous activity pre-dating the development of the main Iceland plume. The crestal erosion surface is probably of Paleocene age and directly associated with a broad regional uplift around Iceland. Its present depth is about one half of that predicted from subsidence models. The depth anomaly probably reflects continued dynamic support from the Iceland plume.