KING'S TROUGH – AN ANCIENT ANALOGUE OF THE TERCEIRA RIFT (NORTH ATLANTIC)

The paper compares the young structures of the Terceira rift and the ancient ones – the King's trough. It was shown that despite the significant difference in the time of their formation, they have much in common. They are located obliquely in relation to all the structures that formed within the Mid-Atlantic Ridge, have a similar extent, and combine parameters characteristic of both continental (superslow rate of extension, thickness of the lithosphere, alkaline volcanism) and oceanic rifts (segmentation, magmatism localized in a narrow area). The stages of formation of the structures are similar. They were formed on the already existing oceanic crust. The initial stage in both cases is associated with diffuse plume tholeiitic magmatism, distributed in some extension area with the formation of large linear uplifts. The second stage was characterized by almost complete cessation of magmatism and localization of extension in a single narrow area. Alkaline magmatism of the central type is typical for the final stage. Both of these structures are part of triple junctions, being fragments of the boundaries of lithospheric plates. The noted similarities indicate the recurrence in time of the kinematics of the movement of lithospheric plates in the North Atlantic with the formation of structures at the plate boundaries that are different in age but similar in geological history and formation mechanisms.