Gravity anomalies of the Mid-Atlantic Ridge north of the Kane fracture zone

High-resolution gravity and multibeam bathymetric data were newly obtained from the Mid-Atlantic Ridge (MAR) between latitudes 23 degrees 30'N and 28 degrees N. Mantle Bouguer anomalies (MBA) show magmatic accretion focused at discrete centers along the spreading axis except near the oblique portion of the MAR between 24 degrees 30'-24 degrees 50'N. The MBA also indicates that crustal production near the TAG hydrothermal field has been relatively low during the last 2-3 My. The MBA show 120 degrees-striking off-axis traces, indicating northward migration of the oblique portion and northward extension of the segments south of the oblique zone despite a long-wavelength southward deepening of the axial topography. Observed gravity anomalies support a tectonic interpretation proposed from morphology and geomagnetic anomalies that the segment south of the oblique zone has extended northward by repeatedly adding short segments which migrated westward through asymmetric spreading in the oblique zone.