The Harz Mountains, Germany: Finite-element modelling of the evolution based on the interpretation of the gravity field

Abstract

The new Bouguer anomaly map of the Harz Mountains based on 60,000 gravity measurements is presented. The interpretation is done by three dimensional (3-D) gravity modelling, mostly concentrating on the granitic intrusions. The Brocken Granite is modelled as a flattish body with maximum thickness of 2.5 km. The Ramberg Granite is up to 8.5 km thick with a northsouth extent of 35 km. The present mass distribution is an important boundary condition for geodynamic investigations using the finite-element method (FEM). It can be shown that the Harz Mountains are not isostatically compensated. Further calculations deal with the Central European Variscan Belt and reveal a horizontal shortening of 600 m for the Harz Mountains. Considering the Harz Mountains as a wrench-fault-system by taking into account an east-west shortening of 1 km results in a calculated uplift of 220 m which is much less than the vertical displacement at the northern boundary fault zone estimated from gravity and seismic studies.