Etude comparee des structures profondes et des anomalies magnetiques allongees reconnues en manche occidentale et en baie d'audierne: Existence possible d'une suture cryptique au nord-ouest du massif armoricain (France)

Abstract

The magnetic anomaly which spreads off the Audierne Bay is caused by an ophiolitic complex which can be studied onshore. This complex, which is a remnant of oceanic crust, separates a monometamorphic Paleozoic unit from a polymetamorphic Precambrian block. Magnetic susceptibilities have been measured on rocks of the complex. Calculated models show that the main magnetic anomaly of the English Channel can be explained by such a kind of rocks. This information completes the study of the deep structures (the main basic intrusion of the English Channel separates a Paleozoic basin from a polymetamorphic basement) and leads us to believe that another oceanic suture exists in the northwestern part of the Armoricain area. The relations between those two sutures are discussed.