The Kolárovo gravity and magnetic anomaly body in a subcrop of the Danube Basin: A new geological interpretation

Abstract

: We provide an analysis of the existing 2D and 3D gravimetric and magnetic interpretations of the well-known and significant Kolárovo gravity and magnetic anomaly, as well as present a new geological interpretation of its origin. It follows that the source of these anomalies is a high-density and highly magnetic crustal body with the following parameters: (a) density contrast is between +0.28 and +0.31 g cm −3 , (b) magnetic susceptibility is ~22000×10 −6 units of SI, (c) the depth of the upper boundary varies from ~4.5 to 6.0 km, (d) the depth of the center of the gravity body is between 8.7 and 12.5 km, and (e) the depth of the lower boundary moves in the interval from above 13 to 20 km. These factors and the inferred tectonic position of the Kolárovo body allow for its interpretation as a possible eclogite/ ultramafite body. It occurs within a belt of magnetic and gravity anomalies tracing the Eo-Alpine high-pressure metamorphic complexes from the Eastern Alps to the Western Carpathians via the northern periphery of the Rába–Hurbanovo– Diósjenő fault zone. We assume that the position of the Kolárovo crustal body resulted from the Oligocene–Lower Miocene uplift of the East Alpine–West Carpathian junction caused by the compressional tectonic regime accompanied by crustal thickening, surface uplift, and erosion of units forming the present basement of the Danube Basin. Simulta-neously, exhumation of the orogenic infrastructure occurred, which thus affected the Eo-Alpine metamorphic complexes, including the anomalous Kolárovo body. Subsequently, during the Middle–Late Miocene rifting and subsidence of the Danube Basin, the Kolárovo body was buried to its present position.