3D model of the deep structure of the Pavlovsk batholite of the Don Terrane (East-Don Orogen)

Abstract

Introduction: Investigations of large granitoid complexes of the continental crust are of utmost importance for the geodynamic reconstruction of its development. Within the Voronezh crystalline massif, a granitoid complex is the Pavlovsk migmatite-granite-granosyenite complex. Until recently, we had very little information about its deep structure, which prevented researchers from developing accurate models of the upper part of the crust for further geodynamic reconstruction. The purpose of our study was to create a 3D petrodensity model of the crust in the Pavlovsk complex based on the interpretation of gravimetric data.

Methodology: To create the crust model, we needed a large amount of geological, geophysical, and petrophysical data, which we acquired using an ArcGIS system. The initial density model of the upper crust was based on the regional density model of the lithosphere, including the density distribution in the sedimentary cover and the petrodensity map of the crystalline basement of Voronezh crystalline massif. The three-dimensional inverse gravimetric problem was solved by means of an anomalous field linear inversion algorithm using an approximate inverse problem operator for a horizontal layer. The iterative solution of the inverse problem was performed on the actual landscape of the studied territory for a discrete dataset. The redistribution of anomalous densities was performed based on the a priori geological and geophysical data.

Discussion: The Pavlovsk migmatite-granite-granosyenite complex was observed at a depth of up to 8 km, with the major volume at a depth between 1 and 6 km. The determined morphological features of the spatial structure of the complex indicate the presence of lateral inhomogeneities in the vertical thickness distribution. The density of granitoids of different phases are close enough, which makes it impossible to identify them using the model. According to the obtained comprehensive model, the Pavlovsk batholite has a shape of a sill-like intrusions with a series of subvertical structures, which are interpreted as potential magma channels. Intrusions of such a form are common for situations when there is a limited dominance of the magma pressure over the lithostatic pressure.

Conclusions: The obtained model of the upper crust based in the geological and geophysical information is compatible with the existing approaches to the nature of the Pavlovsk migmatite-granite-granosyenite complex. The suggested model can be used in geodynamic constructions of the evolution of Voronezh crystalline massif.