The aeromagnetic map of the French Cadomian belt

Abstract In order to obtain an image of the subsurface of the Armorican Massif, two detailed aeromagnetic surveys were combined to obtain an aeromagnetic map at 350 m altitude with an interpolated grid of 250 m×250 m. The map shows good correlation between the magnetic anomalies and known geological structures and also distinguishes between long- and short-wavelength anomalies. The long-wavelength anomalies are associated with the overall subsurface arcuate structure of the Cadomian belt. The short-wavelength anomalies are commonly associated with the Lanvollon acid volcanic rocks and syntectonic diorites, with one set of short-wavelength anomalies in the east of the Saint-Malo region being associated with dykes that are exposed onshore and continue offshore.

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