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Three-dimensional crustal model of the Dinarides and marginal areas based on gravity and seismic models

The survey area includes the Dinarides and the peripheral areas of the Pannonian Basin and the Adriatic Sea, and it’s located at the collision of the Adriatic microplate and the Pannonian tectonic segment of Eurasia. The basic goal of the research is to determine a three-dimensional geological model of the crust and the uppermost mantle based on three-dimensional gravity and seismic models. The density model was determined based on 2D- gravity modelling according to the methodology applied by Šumanovac (2010). Gravity modelling is characterized by relatively wide ambiguity limits, but using the so-called "calibrated density set", they can be significantly constricted. The modelling was performed on the Alp07 profile and five gravity profiles placed approximately perpendicular to the Dinarides extension. The basic assumption is that the structure of the Dinarides is generally two-dimensional. This would mean that the geological properties along the Dinarides do not change, so the calibration of the density set is made on the Alp07 profile in the northern Dinarides. The two-dimensionality of the geological structure is clearly evident on regional geological and gravity maps, especially the Bouguer anomaly map. Based on two-dimensional density models of gravity profiles, a three- dimensional density model was developed, which clearly presents the relationships in the survey area. Two velocity models were constructed. The first model was constructed by converting the density model into velocities. The procedure opposite to the determination of the calibrated density set is now used. However, this transfer is now made on a 3D-density model, so a 3D-velocity model has been constructed to be able to correlate with the velocity model obtained by seismic method. The second velocity model of the Dinarides and marginal areas was determined by local earthquake tomography by means of inverse seismic modelling. By correlating all geophysical models, the first three-dimensional geological model in the area of the Dinarides and marginal areas was determined. The smallest thicknesses of the crust, only about 20 km, are located below the Pannonian Basin, and the crust is apparently single-layered. Small crust thicknesses, 25-30 km, are also found in the Adriatic Sea, the area of the undeformed Adriatic microplate. Beneath the Dinarides the crust thickens abruptly, and the greatest thicknesses lie below the centre of the Dinarides in a narrow and regular zone with a Dinaridic extension. The width of the Moho depression along the Dinarides is largely similar, but the maximum depths of the Moho changing from 45 km in the northern to 50 km in the southern Dinarides. Between the two-layer Dinaridic crust, which includes the Adriatic units, and the single-layer Pannonian crust, which includes European units, there is a wide Transitional Zone. It plays the role of a suture zone of two continents, Africa and Europe. The most prominent phenomenon is the high density body below the Sava Depression, which can be interpreted as a larger block of oceanic crust rocks.

Three-dimensional crustal model ; Dinarides ; gravity model ; seismic model

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