Early Jurassic Magmatism of the Kobyumé Graben System (Verkhoyansk Framing of the Siberian Craton) and Its Geodynamic Nature

Abstract

Data on the Early Jurassic volcanic rocks of the Kobyume graben system, which formed at the Verkhoyansk passive margin of the Siberian Craton, are presented. The volcanic complex contains products of basaltic eruptions that occurred under conditions of a shallow sea. The basalts have elevated TiO2 contents (>1.8 wt%), and variations of their composition were controlled by fractionation processes. By their geochemical characteristics, the volcanic rocks are transitional between ocean island basalts and enriched basalts of mid-oceanic ridges. Taking into account the remote location of the Kobyume graben region from the convergent boundaries of lithospheric plates and from the nearest areas of contemporaneous magmatism, the data obtained support the conclusion that the Kobyume tectono-magmatic areal is a result of a small mantle plume effect onto the passive margin of the Siberian continent.