The deep structure of the Western Verkhoyansk sector of the Verkhoyansk fold and thrust belt according to geophysical data

The Verkhoyansk fold and thrust belt (VFTB) is the largest geological structure in the Verkhoyansk–Kolyma orogenic region. Despite decades of study of the Verkhoyansk fold and thrust belt, the region’s deep structure remains poorly understood. Existing models and schematics of the region’s lithospheric structure are based primarily on the interpretation of key seismic profiles located in the northern end and South Verkhoyansk sector of the fold and thrust belt. The aim of this study is to summarize the available data and analyze anomalous geopotential fields and their transforms to clarify the deep structure.

This paper presents the results of geophysical surveys of the West Verkhoyansk sector and adjacent territories of the Verkhoyansk fold and thrust belt. To obtain information on the distribution of magnetic and density heterogeneities, higher-order derivatives were recalculated in the Oasis Montaj geoinformation system, and two- dimensional energy filtering with separation of fields into mid- and low-frequency components was performed in the automated COSCAD 3D program. To study the deep structure of the study area by solving an inverse problem in COSCAD 3D, magnetic and gravity models were calculated to estimate the parameters of anomaly-forming objects.

The data obtained allowed us to clarify the tectonic structure and distribution of igneous formations and estimate the depths of magnetic and density heterogeneity sources in the West Verkhoyansk sector of the Verkhoyansk fold and thrust belt. Hidden tectonic faults with sublongitudinal and east-northeast strikes were identified. The position of the West Verkhoyansk buried rift graben was demonstrated. The resulting geophysical models revealed three structural stages, with different magnetic and density mass source positions, correlating with the sedimentary cover and the upper and lower crust.

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