Abstract
The crustal structure along a 312 km transect, stretching from the
axial mountains of the North Atlantic Knipovich Ridge to the continental
shelf of Svalbard, has been obtained using seismic reflection data
and wide angle OBS data. The resulting seismic Vp and Vs models are
further constrained by a 2-D-gravity model. The principal objective
of this study is to describe and resolve the physical and compositional
properties of the crust in order to understand the processes and
creation of oceanic crust in this extremely slow-spreading counterpart
of the North Atlantic Ridge Systems. Vp is estimated to be 3.50-6.05
km/s for the upper oceanic crust (oceanic layer 2), with a marked
increase away from the ridge. The measured Vp of 6.55-6.95 km/s for
oceanic layer 3A and 7.10-7.25 km/s for layer 3B, both with a Vp/Vs
ratio of 1.81, except for slightly higher values at the ridge axis,
does not allow a clear distinction between gabbro and mantle-derived
peridotite (10-40\% serpentized). The thickness of the oceanic crust
varies a lot along the transect from the minimum of 5.6 km to a maximum
of 8.1 km. The mean thickness of 6.7 km for the oceanic crust is
well above the average thickness for slow-spreading ridges (<10 mm/year
half-spreading rate). The areas of increased thickness could be explained
by large magma production-rates found in the zones of axial highs
at the ridge axis, which also have generated the off-axial highs
adjacent the ridge. We suggest that these axial and off-axial highs
along the ridge control the lithological composition of the oceanic
crust. This approach suggests normal gabbroic oceanic crust to be
found in the areas bound by the active magma segments (the axial
and off-axial highs) and mantle-derived peridotite outside these
zone.
Users
Please
log in to take part in the discussion (add own reviews or comments).