U-Pb dating, oxygen and hafnium isotopic ratios of zircon from rocks of oceanic core complexes at Mid-Atlantic Ridge: evidence for an interaction of young and ancient crusts at spreading of the ocean floor

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Abstract

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 δ18O 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.

About the authors

N. S. Bortnikov

Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences

Email: silantyev@geokhi.ru

Academician of the Russian Academy of Sciences

Russian Federation, 35, Staromonetny, Moscow, 119017

S. А. Silantiev

Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences

Author for correspondence.
Email: silantyev@geokhi.ru
Russian Federation, 19, Kosygin street, Moscow, 119991

F. Bea

University of Granada

Email: silantyev@geokhi.ru

Foreign Member of the Russian Academy of Sciences

Spain, Avda. del Hospicio, Granada, 18010

P. Montero

University of Granada

Email: silantyev@geokhi.ru
Spain, Avda. del Hospicio, Granada, 18010

T. F. Zinger

Institute of Precambrian Geology and Geochronology of the Russian Academy of Sciences

Email: silantyev@geokhi.ru
Russian Federation, 2, Makarova embankment, St.Petersburg, 199034

S. G. Skolotnev

Geological Institute of the Russian Academy of Sciences

Email: silantyev@geokhi.ru
Russian Federation, 7, Pyzhevsky lane, Moscow, 119017

E. V. Sharkov

Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences

Email: silantyev@geokhi.ru
Russian Federation, 35, Staromonetny, Moscow, 119017

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