Basement segmentation and tectonic structure of the Lomonosov Ridge, arctic Ocean: Insights from bedrock geochronology

Abstract

Apparent variations in the morphology of the Lomonosov Ridge and its along-strike segmentation are caused by the heterogeneity of the basement. Based on the morphological diversity, we divide the Lomonosov Ridge into three segments: Siberian, Central and North American. New petrographic and geochronological data from the rock clasts sampled in the “Arctika-2007-1” expedition, are integrated with seismic and relevant mineralogical, petrographic and isotopic data. Recovered fragments of the high-grade metamorphic and siliciclastic rocks are attributed to the bedrock of the Siberian and Central Segments of the Lomonosov Ridge respectively.The mineralogical and isotopic analysis of detrital zircons from Neoproterozoic arkose defines the Grenvillian age for the basement of the Siberian Segment of the Lomonosov Ridge. The U-Pb dating of the metamorphic zircons from gneisses and schists suggests that Timanian crystalline basement of the Central Segment was affected by an upper-Ordivician (∼450 Ma) felsic magmatism, followed by the mid- to high-grade Caledonian tectonometamorphic event (∼400 Ma). The Central Segment is therefore inferred to be a frontal part of Caledonian convergent shear and fold zone.Caledonian deformation front is suggested between the northeastern and southwestern islands of De Long archipelago. Northward from the shelf break, the orogenic front is expected between the Geophysicists Spur and the main horst of the Siberian Segment. Within the Central Segment the Caledonian deformation front is inferred to stretch along the western flank of the Lomonosov Ridge.