Basalts of a Seamount on the Eastern Flank of the Charlie Gibbs Transform Fracture Zone, North Atlantic: Petrochemical and Isotopic Evidence of a Microplume-Affected Formation in the Axial Zone of the Mid-Atlantic Ridge

The composition of basalts dredged from the slopes of a single seamount (guyot), which is located south of the eastern end of the Charlie Gibbs Fracture Zone in the North Atlantic, is studied. Groups of high- and low-Ti rocks, which belong to oceanic tholeiites of the E-MORB and T-MORB types, respectively, are recognized. The first group of basalts have higher contents of TiO 2 , Na 2 O, K 2 O, P 2 O 5 , Fe 2 O 3 , and incompatible trace elements. The basalts of both groups are similar in the normalized lithophile element patterns indicating their melting from a similar mantle substrate. The difference in their composition is probably caused by melting of high-Ti volcanic rocks at a deeper intermediate level between spinel and garnet facies. Our studies give grounds to believe that the seamount also formed as a large neovolcanic rise 64–67 Ma ago under the influence of a microplume, which was a branch of the Milne deep mantle plume.