Gravity anomaly and density distribution of the Rhenish Massif.

Abstract

The study aims to explain the Bouguer anomaly by a geometric model of deep Rhenish massif structure constructed on the basis of available seismological, geological and other data. Well reproduced are the gravity decrease towards the Alps, the regional Rhine graben anomaly, the positive values of the E massif, with highs in the Odenwald/Spessart, Bergisches Land/Sauerland and the Harz regions and the negative values of the western massif; not reproduced is the gravity high of the Palatine, calling for a high-density mass in the crustal layers. The Eifel low-velocity body in the sub-crustal lithosphere has no conspicuous gravity effect, whilst the southern Rhine graben shows little velocity decrease but a clear density contrast of the order of -0.05 g/cm3. In both regions the computed densities are in excellent agreement with isostatic estimates. The discrepancy between the velocity-density characteristics of both anomalies suggests that besides heating, fluid phases affect uplift and volcanism.-J.M.H.