3D implicit geomodelling in the metamorphic units of the Italian Western Alps (Aosta Valley, Italy)

3D geological modelling of complex metamorphic settings that underwent a sequence of ductile and brittle deformation events is an extremely challenging task. In this contribution, we propose a workflow that deals with sparse and heterogeneous in density input data, based on structural interpretation in cross-sections followed by fully 3D implicit modelling. Complex geometries are involved: isoclinal folds, large volume variations of the lithological bodies, tectonic contacts between large-scale tectono-metamorphic units, thin tectonic slices, lenticular bodies, and many others. For such setting, among commercial geomodelling software packages no out-of-the-box modelling workflow is available. Our workflow therefore proposes to “cheat” on the geological meaning of some entities (e.g. lithological boundaries and tectonic contacts) in order to obtain a 3D model that properly fits the available data. A general description of the workflow is illustrated with practical examples from the study area.