Crustal structure of the ultra-slow spreading Knipovich Ridge, North Atlantic, along a presumed ridge segment center

Abstract

A combined ocean bottom seismometer, multichannel seismic reflection and gravity study has been carried out along the spreading direction of the Knipovich Ridge over a topographic high that defines a segment center. The youngest parts of the crust in the immediate vicinity of the ridge reveal fractured Oceanic Layer 2 and thermally expanded and possibly serpentinized Oceanic Layer 3. The mature part of the crust has normal thickness and seismic velocities with no significant crustal thickness and seismic velocity variations. Mature Oceanic Layer 2 is in addition broken into several rotated fault blocks. Comparison with a profile acquired *40 km north of the segment center reveals significant differences. Along this profile, reported earlier, periods of slower spreading led to generation of thin crust with a high P-wave velocity (Vp), composed of a mixture of gabbro and serpentinized mantle, while periods of faster spreading led to generation of more normal gabbroic crust. For the profile across the segment center no clear relation exists between spreading rate and crustal thickness and seismic velocity. In this study we have found that higher magmatism may lead to generation of oceanic crust with normal thickness even at ultra-slow spreading rates.

An integrated geophysical study of Vestbakken Volcanic Province, western Barents Sea continental margin, and adjacent oceanic crust

“…This is in accordance with most surrounding oceanic mantle velocities (Breivik et al 2003;Czuba et al 2011;Kandilarov et al 2010;Libak et al 2012;Mjelde et al 2002).…”

“…The layer reaches a maximum thickness of 6-7 km between km 75 and km 125. A similar thickness in oceanic layer 3 is observed off axis on the ultraslow Knipovich Ridge (Kandilarov et al 2010), on an expected magmatic center of this ridge. However, that crust has lower average velocities (~6.7 km/s) than in our model.…”

“…However, that crust has lower average velocities (~6.7 km/s) than in our model. Moreover, the thick crustal segment in Kandilarov et al (2010) is relatively narrow (~30 km) while our thick crust is observed over an interval more than 100 km wide. Along axis seismic studies from the ultraslow Southwest Indian Ridge show that the magmatic segment centers are typically 20-30 km wide (Minshull et al 2006).…”

“…This is significantly thicker than most of the surrounding oceanic crust (Jackson et al 1990;Kandilarov et al 2010;Klingelhöfer et al 2000;Libak et al 2012). However, Mjelde et al (2002) observed a 7-8 km thick oceanic crust west of the COB on the Senja margin and Kandilarov et al (2010) reported areas with 7-8 km thick oceanic crust on the eastern side of the Knipovich Ridge interpreted as crust accreted at a magmatic dominated spreading segment. Modeling shows that a spreading ridge is able to produce an igneous crust thicker than 8 km only if mantle temperatures are higher than normal (Bown and White 1994).…”

The Cenozoic western Svalbard margin: sediment geometry and sedimentary processes in an area of ultraslow oceanic spreading

“…We note, however, that Anomalies 5 (9.8 Ma; Cande and Kent 1995), 6 (19.6 Ma) and 7 (24.6 Ma) have been identified in a distance between c. 50 and 150 km from the Knipovich Ridge rift valley ( Fig. 2a) (Engen et al 2008;Kandilarov et al 2008Kandilarov et al , 2010.…”