The crustal structure of the Kane fracture zone from seismic refraction studies
Citable URI
https://hdl.handle.net/1912/9605Location
Kane Fracture Zone24°N, 44°W
DOI
10.1575/1912/9605Abstract
A detailed seismic refraction experiment was carried out across the Kane Fracture Zone near 24°N,
44°W using explosive and air gun sound sources and eight ocean bottom hydrophone receivers. The
shooting lines and receive rs formed a 'T' configuration across the fracture zone, with two receivers located
about SO km apart in the fracture zone trough and the remaining six receivers positioned 25-30 km
apart on either side of the fracture zone. The crustal thicknesses and velocities observed at the receivers
located north and south of the Kane Fracture Zone fall within the range of those typically observed for
normal oceanic crust. There is no convincing evidence for signficantly different crustal thicknesses or upper
mantle velocities on either side of the fracture zone despite a 10-m.y. age difference. Anomalously
thin crust is present beneath the Kane Fracture Zone trough with total crustal thicknesses of only 2-3
km, about half the thickness of normal oceanic crust. This crust is also characterized seismically by low
compressional wave velocities (~4.0 km/s) at shallow depths and the absence of a normal layer 3 refractor.
This anomalous crust extends over a width of a t least 10 km. Dense, high-velocity mantle type material
may also exist at shallow depths beneath the adjacent Kane Fracture Zone ridge. Results from other
geological and geophysical studies of fracture zones suggest that this type of crustal structure may by typical
of many Atlantic fracture zones. We propose that the anomalously thin crust found within these fracture
zones is a primary feature caused by the accretion of a thinner volcanic and plutonic layer within the
fracture zone. This anomalous crust, which probably is restricted to a zone no wider than a typical transform
fault valley (~10 km) in most cases, is inferred to consist of a few hundred meters of extrusive basalts
and dikes overlying about 2 km of gabbro and metagabbro, possibly interbedded with ultramafics.
This anomalously thin crustal section may be extensively fractured and brecciated at shallow levels by
faulting in the active transform domain. A relatively narrow zone of thin crust within fracture zones can
ex plain a number of geological and geophysical characteristics of fracture zones including the depth of
the transform fault valley and the exposure of deep crustal and upper mantle rocks in the walls of fracture
zones.
Description
Also published as: Journal of Geophysical Research 85 (1980): 3759-3777
Collections
Suggested Citation
Detrick, R. S., & Purdy, G. M. (1980). The crustal structure of the Kane fracture zone from seismic refraction studies. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/9605Related items
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