The terms "boudin" and "boudinage"' were first introduced, as descriptive terms, for particular geometric features associated with quartz veins in competent metaquartzitic layers in the High-Ardenne Slate Belt (Belgium). The occurrence of the "boudins" has subsequently been used to draw kinematic conclusions on a pre-Variscan extensional event in the Rhenohercynian belt. In this paper, a combined structural and fluid-inclusion approach allows proposing a new and more representative kinematic model for the development of the veins and associated structures, Moreover, the kinematic significance of "interboudin" veins is emphasized. In this regard, microthermometry of primary CO2-N-2 fluid inclusions in the quartz of the "interboudin" veins suggests that the origin of vein development is hydraulic fracturing in an already compressional setting. This suggestion implies the presence of fluid and near-lithostatic fluid pressures to permit fracturing at great depths where the rocks otherwise would be either stable or in the realm of ductile behaviour. The vein filling fluid had a local origin and was most likely related to the formation of bedding-parallel dissolution seams within the host rock. Veining is followed by layer-parallel shortening, resulting in the development of "double-sided" mullions at both interfaces of metaquartzitic layers, pinned by pre-existing veins. Subsequently, these polyphase structures behave passively in the Variscan deformation. (C) 2002 Elsevier Science B.V. All rights reserved.