Crustal Structure of the Mendeleev Rise in the Arctic Ocean: Synthesis of Seismic Profiles and Rock Sampling Data

Abstract

The Mendeleev Rise is located in the Amerasian Basin of the Arctic Ocean. The study synthesizes interpretations of regional seismic profiles of the 2D CDP seismic reflection method and rock survey data using special underwater vehicles on the slopes of seamounts and scarps. The rise is represented by alternating highs (horsts) and half-grabens. At the base of the horst sections, bright reflectors are distinguished, interpreted as volcanic rocks. The half-graben sections are wedge-shaped in section view and are similar in geometry to seaward-dipping reflectors (SDR) of continental passive volcanic margins. Rock sampling has shown that the horsts consist of the Paleozoic sedimentary rocks penetrated by intrusions. The Aptian–Albian sections with volcanics (basalts, trachybasalts, trachyandesites) were identified on the horsts. U/Pb dating of igneous rocks has showed that typical age of the rocks is 110–114 Ma. The Cretaceous igneous rocks contain zircons with ages ranging from the Pre-Barremian Mesozoic to Paleozoic and Precambrian. These zircons were captured by basaltic magma during its upward movement. The presence of these ancient zircons indicates that the Mendeleev Rise consists of the continental crust. A model of the crustal structure of the Mendeleev Rise is proposed. The base of the section visible on seismic profiles is characterized by predominance of volcanics (from basalts to trachyandesites on horsts and basically basalts in half-grabens). The upper and lower crust is approximately 20–30% replete with intrusions. At the base of the crust, a high-velocity layer up to 5 km thick is distinguished. It is assumed that its lower part is entirely represented by gabbro-type intrusions, and the upper part is the lowest part of the lower crust, maximally saturated with intrusions.