Seismic data and ancient zircons discovered on the Mendeleev Rise, Arctic Ocean, indicate continental crust

Abstract

The Alpha-Mendeleev Rise is located in the Amerasia Basin. The work is based on a synthesis of interpretation of regional 2D MCS seismic profiles and data from rock sampling using special underwater vehicles on the slopes of seamounts. The Rise is represented by alternation of highs (horsts) and half-grabens. At the base of the horst cover, bright reflectors are distinguished, which are interpreted as volcanics. Half-graben sections are wedge-shaped and are similar in geometry to seaward-dipping reflectors (SDRs) of continental passive volcanic margins. Rock sampling has shown that the horsts are composed of sedimentary rocks of Paleozoic age, penetrated by intrusions. Aptian-Albian sections with volcanics (basalts, trachybasalts, trachyandesites) were identified on the horsts. U/Pb dating of igneous rocks showed that typical age of rocks is 110-114 Ma. Magmatic Cretaceous rocks contain zircons with ages ranging from pre-Barremian Mesozoic to Precambrian. The presence of these ancient zircons indicates that the Alpha-Mendeleev Rise is composed of continental crust. A model of the crustal structure of the Alpha-Mendeleev Rise is proposed. The upper and lower crust is approximately 20-30% saturated with intrusions of basic composition. At the base of the crust, a high-velocity layer up to 5 km thick is distinguished.