Deep Structure of the Eastern Margin of the Siberian Craton, NE Russia: Evidence from Analysis of an Anomalous Gravitational Field

Abstract

The paper presents the results of a study of the anomalous gravitational field of the Verkhoyansk fold-and-thrust belt. The belt is located on the eastern margin of the Siberian craton and represents the frontal part of the accretion-collision Verkhoyansk-Kolyma folded area (Northeastern Russia). The base of the fold-thrust belt is the pre-Mesoproterozoic crystalline basement, overlain by sedimentary strata. The purpose of this study is to clarify the features of the deep structure of the Verkhoyansk fold-and-thrust belt based on an analysis of modern geological and geophysical data. According to the results of the analysis of the gravitational field Δg, the Yana, Tompo-Gornostakh gravity maxima and the West Verkhoyansk, Derbekin and South Verkhoyansk gravity minima are identified. Regional anomalies Δg reflect relatively upstanding and downdip blocks of the Verkhoyansk fold-and-thrust belt basement. The maximum subsidence of the surface of the crystalline basement is observed in the South Verkhoyansk sector, the minimum – in the Sette-Daban tectonic zone. The Adycha-Elgin tectonic zone is characterized by a heterogeneous block structure of the basement. In the area of the Kitchansky uplift, a subvertical scarp is identified in the crystalline basement relief. Gravitational anomalies corresponding to magmatic plutons and regional fault structures are identified. The confinement of anticlinoria of the West Verkhoyansk sector to local gravitational anomalies of a negative sign is noted. The correlation of the boundaries of tectonic zones with linear alternating anomalies Δg is determined.