Seafloor geomagnetic vector anomaly of the intersection of the Mid‐Atlantic Ridge and the Kane Transform Fault: Implications for magnetization of the oceanic crust

Abstract

We investigated the fine‐scale magnetic structure of the oceanic crust and upper mantle around the western intersection of the Mid‐Alantic Ridge and the Kane Transform Fault, using the geomagnetic vector field measured at the seafloor. The strikes of magnetic boundaries were found to reflect of the local tectonics represented by fault strikes and dips. The ridge‐transform intersection is characterized by magnetic boundary strikes rotated eastward. The strike directions reflect the direction of recent magmatic activity. These indicate that a few traces of faults extending obliquely from the ridge axis to the transform fault are associated with neovolcanism. Magnetic boundary strikes in the lower part of the transform valley wall and near a linear trace of the transform fault indicate deformation or tilting of the crust associated with transform faulting. It is also indicated that the crustal block around the median ridge is tilted by uplift, accompanied by injection or emplacement and serpentinization of peridotites. The nodal basin consists of extrusive basalts in the E–W direction and N–S trending magnetic strikes. Submersible observation of in situ magnetization of oceanic crust shows that extrusive basalts are typically strongly magnetized. The most recent neovolcanic ridge has a mean magnetization of 50 A/m. The mean magnetization of the ridge axis is 20 A/m. The magnetization of the 3 Ma ridge flank in the inside corner high is about 10 A/m. The gabbroic layer in the transform valley has a magnetization less than 2 A/m. The serpentinized peridotites in the median ridge have magnetization less than 1 A/m. This magnetization records a reversal in polarity, which is important because the serpentinized peridotites contribute to the marine geomagnetic anomaly pattern.