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U-Pb age, oxygen and hafnium isotopic ratios in zircon from rocks of ocean core complexes at Mid-Atlantic Ridge have been studied using SHRIMP and MC-LA-ICP-MS techniques. U-Pb dating revealed four group of zircons: 1) 0,6-1,7 Ma, 2) 6,7-11,2 Ma, 3) 12,9-17,6 Ma, 4) 200 to 2044 Ma. The 18O values range from 4,74 to 7,2 and are distinct for zircon grains of different ages. Hafnium isotopic ratio for zircon aged from 0,6 to 17,6 Ma corresponds or is close to that of MORB from Central Atlantic. The oxygen and hafnium isotopic compositions of zircon elder than 280 Ma correspond to those of the sialic continental crust. A hypothesis of involvement of the ancient pre-Atlantic sialic (280 млн лет) and old Atlantic (7-17 Ma) crusts in a generation of the contemporary (young) oceanic crust during formation of the slow-spreading Mid-Atlantic Ridge has been proposed.

The results of study of Fe-Mn crusts from the Mendeleev Rise in the Arctic Ocean in 2016 sampled with manipulators from a submarine are presented. Concentrations of Fe, Mn, Co, Ni, Zn, Cu, Cr and Pb are measured in collected Fe-Mn crusts. The variations in the content of these elements are determined by the chemical properties of the elements, the height of the underwater topography, the composition of the underlying substrate and the presence of bottom silt.