GRAVITY-ANOMALIES OF THE MID-ATLANTIC RIDGE NORTH OF THE KANE FRACTURE-ZONE

High-resolution gravity and multibeam bathymetric data were newly obta ined from the Mid-Atlantic Ridge (MAR) between latitudes 23 degrees 30 'N and 28 degrees N. Mantle Bouguer anomalies (MBA) show magmatic accr etion 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 hydrothe rmal field has been relatively low during the last 2-3 My. The MBA sho w 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 t he axial topography. Observed gravity anomalies support a tectonic int erpretation proposed from morphology and geomagnetic anomalies that th e segment south of the oblique zone has extended northward by repeated ly adding short segments which migrated westward through asymmetric sp reading in the oblique zone.