NEW DATA ON THE COMPOSITION OF BASALTS FROM SEAMOUNT NEAR THE EASTERN FLANK OF THE CHARLIE GIBBS FZ (NORTH ATLANTIC)

Abstract

Composition of basalts collected from the slopes of a single seamount (guyot) located south of the eastern flank of the Charlie Gibbs FZ in the North Atlantic, was studied. High-titanium and low-titanium groups related respectively to E-MORB and T-MORB oceanic tholeites, were singled out. Basalts of the first group are characterized by higher concentrations of TiO2, Na2O, K2O, P2O5, Fe2O3 and incoherent trace-elements. Basalts of both groups were melted from a mantle substrate of similar composition, which is a mixture of DM and HIMU mantle material and to a lesser extent – EM-2. Their difference in composition is due to the fact that high-titanic melts were formed deeper at a level between the spinel and garnet facies. Basalts similar in petro-geochemical and isotopic parameters were found in the axial zone of the Mid-Atlantic Ridge between the Charlie Gibbs and Maxwell FZ, where they compose large neovolcanic edifices formed with a sharp increase in the intensity of axial magmatism as a result of microplumes rise. Our studies give grounds to believe that the studied seamount was also formed as a large neovolcanic structure 64–67 million years ago under the influence of a microplume, which was branch of the Milne plume of the deep mantle.