Abstract

A complete bathymetry and geophysical survey of the recent domain of the Mid-Atlantic Ridge north of the Azores, between 40°30′N and 45°N, was achieved during the 1998 Triatnord cruise of R/V L'Atalante. Interpretation of along-track data and geochemical analyses of rock samples show that the surveyed section represents a peculiar section of the Mid-Atlantic Ridge. This new data set allows us to tentatively place the northern limit of the influence of the Azores hotspot on the accretion processes between lat 43°N and 44°N. This limit is marked by a 1° wide transition zone. This fits well with the asymmetry of the upper mantle thermal structure, as previously inferred from seismic tomography and geoid models, thus enhancing the links between shallow and deeper accretion processes in a hotspot-ridge interaction context. Observations of along-ridge variations of geochemical parameters at various scales shed light on the relations between mantle (geochemical) heterogeneities and the accretion processes along the ridge axis, confirming the asymmetry in the along-ridge horizontal extent of the Azores plume.

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