Identification of the magnetization low of the Lucky Strike hydrothermal vent using surface magnetic data

[1] Two surface magnetic surveys, covering the Lucky Strike hydrothermal area, are merged into a single magnetic anomaly description, which, when inverted in the presence of topography, shows a magnetization low at the segment center, close to the central volcano, in the middle of which is located the hydrothermal vent. To test if this magnetization is in any way connected with the hydrothermal vent field, we devised a method to distinguish a ‘‘regional’ ’ field that can be attributed to the ‘‘normal’ ’ spreading geometry from the ‘‘local’ ’ field that can be attributed to the hydrothermal vent area itself. This is achieved by the computation of a three-dimensional regional magnetic field that takes into consideration bathymetry, location of the ‘‘zero-age’ ’ axis, asymmetry in the half spreading rates, magnetization decay with age, polarity reversals, and the transition between consecutive magnetic blocks. This model was fitted to the observed surface magnetic data, and the ‘‘magnetic residual’ ’ was inverted to allow a better definition of the magnetization anomalies. We show that as far as surface magnetic data are concerned, the magnetization low has only partial correlation with the hydrothermal field and is the signature of a relatively large area in which bulk magnetization is lower than average