Relation between Magmatic and Tectonic Processes in the Formation of the Oceanic Crust to the South of the Charlie Gibbs Fracture Zone (North Atlantic)

Abstract

The article presents new data on the structure and relationship of tectonic and magmatic processes during the formation of the Mid-Atlantic Ridge between the Charlie Gibbs and Maxwell fracture zones in the North Atlantic. It is shown that this region is characterized by significant reduction in volcanism, which leads to the excavation of low crustal and upper mantle rocks to the surface. Both individual inland oceanic complexes of the most varied configurations and extended sublatitudinal ridges composed of plutonic rocks are formed. Our analysis showed that this formation setting existed for at least 14‒16 Ma. The formation of most internal oceanic complexes is associated not only with tectonic factors, but also with the serpentinization of peridotites, which leads to a decrease in density, an increase in volume, and, as a result, to the emergence of large ultrabasic massifs, including separated blocks of gabbroids, dolerites, and basalts. Numerous zones of sliding, crushing, abrasion and deformation of rocks indicate tectonic movements. The study region is characterized by numerous non-transform displacements of different amplitudes, which are formed under conditions when relative displacements of oceanic lithosphere segments are realized in wide areas undergoing shear and extension deformations. The morphology of the emerging tectonic-magmatic structures of the region is determined by tectonic factors. The exceptions are cases when the volumes of melts entering the surface in a short period of time are significantly higher than the average for a certain segment of the rift valley. The analysis performed shows the presence within the region of sources of magnetic anomalies that are heterogeneous in nature, both of volcanic origin and associated with manifestations of superimposed tectonic activity.