Preprints
https://doi.org/10.5194/se-2021-98
https://doi.org/10.5194/se-2021-98

  17 Aug 2021

17 Aug 2021

Review status: a revised version of this preprint is currently under review for the journal SE.

Crustal structure of the Volgo-Uralian subcraton revealed by inverse and forward gravity modeling

Igor Ognev1, Jörg Ebbing2, and Peter Haas2 Igor Ognev et al.
  • 1Institute of Geology and Petroleum Technologies, Kazan Federal University, 4/5 Kremlyovskaya street, Kazan 420008, Russia
  • 2Department of Geosciences, Kiel University, Otto-Hahn Platz 1, Kiel, D-24118, Germany

Abstract. Volgo-Uralia is a Neoarchean easternmost part of the East European craton. Recent seismic studies of the Volgo-Uralian region provided new insights into the crustal structure of this area. In this study, we combine satellite gravity and seismic data in a common workflow to perform a complex study of Volgo-Uralian crustal structure which is useful for further basin analysis of the area. In this light, a new crustal model of the Volgo-Uralian subcraton is presented from a step-wise approach: (1) inverse gravity modeling followed by (2) 3D forward gravity modeling.

First, inversion of satellite gravity gradient data was applied to determine the Moho depth for the area. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region, and the model is constrained by the available active seismic data.

The Moho discontinuity obtained from the gravity inversion was consequently modified and complemented in order to define a complete 3D crustal model by adding information on the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling where both seismic and gravity constraints were respected. The obtained model shows crustal thickness variations from 32 to more than 55 km in certain areas. The thinnest crust with a thickness below 40 km is found beneath the Pericaspian basin, which is covered by a thick sedimentary layer. The thickest crust is located underneath the Ural Mountains as well as in the center of the Volga-Uralian subcraton. In both areas the crustal thickness exceeds 50 km. At the same time, initial forward gravity modeling has shown a gravity misfit of ca. 95 mGal between the measured Bouguer gravity anomaly and the forward calculated gravity field in the central area of the Volga-Uralian subcraton. This misfit was interpreted and modeled as a high-density lower crust which possibly represents underplated material.

Our preferred crustal model of the Volga-Uralian subcraton respects the gravity and seismic constraints and reflects the main geological features of the region with Moho thickening in the cratons and under the Ural Mountains and thinning along the Paleoproterozoic rifts, Pericaspian sedimentary basin, and Pre-Urals foredeep.

Igor Ognev et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2021-98', Anonymous Referee #1, 11 Sep 2021
    • AC1: 'Reply on RC1', Igor Ognev, 17 Nov 2021
  • RC2: 'Comment on se-2021-98', Anonymous Referee #2, 12 Oct 2021
    • AC2: 'Reply on RC2', Igor Ognev, 17 Nov 2021
    • AC3: 'Reply on RC2', Igor Ognev, 21 Nov 2021

Igor Ognev et al.

Data sets

Crustal structure of the Volgo-Uralian subcraton revealed by inverse and forward gravity modeling [dataset] Igor Ognev, Jörg Ebbing, Peter Haas https://doi.org/10.5281/zenodo.5151503

Igor Ognev et al.

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Short summary
We present a new 3D crustal model of Volgo-Uralia, an eastern segment of the East European craton. We built this model by processing the satellite gravity data and used prior crustal thickness’ estimations from regional seismic studies to constrain the results. The modeling revealed a high-density body on the top of the mantle and otherwise reflected the main known features of Volgo-Uralian crustal architecture. We plan to use the obtained model for further geothermal analysis of the region.