A NEW LOOK AT BELGIAN AEROMAGNETIC AND GRAVITY-DATA THROUGH IMAGE-BASED DISPLAY AND INTEGRATED MODELING TECHNIQUES

Digital processing and image-based display techniques have been used t o generate contour and shaded-relief maps of Belgian aeromagnetic data at a scale of 1:300 000 for the whole of Belgium. These highlight the important anomalies and structural trends, particularly over the Brab ant Massif. North and vertically illuminated shaded-relief plots, enha nced structural belts trending west-east to northwest-southeast in the Brabant Massif and west-east to southwest-northeast in the core of th e Ardennes. The principal magnetic lineaments have been identified fro m the shaded-relief plots and tentatively correlated to basement struc tures. Most short lineaments are correlated with individual folds whil e the more extensive lineaments are correlated with large scale fault structures. Magnetic highs within the Brabant Massif are attributed to folded sediments of the Tubize Group. The magnetic basement in the ea st of Belgium is sinistrally displaced to the north by an inferred dee p NNW-SSE crustal fracture. The Bouguer anomaly map of Belgium identif ies the Ardennes as a negative area, and the Brabant Massif as a posit ive area, with the exception of a WNW-trending gravity low in its west ern part. The southern margin of the Brabant Massif is defined by a st eep gravity gradient coincident with the Faille Bordiere (Border Fault ). Trial modelling of the gravity and magnetic data, carried out along profiles across the Brabant and Stavelot massifs, has identified prob able acid igneous intrusions in the western part of the Brabant Massif , and a deep magnetic lower density body underlying the whole Ardennes region, which is thought to be a distinctive Precambrian crustal bloc k.