Origin and migration pattern of palaeofluids during orogeny: discussion onthe Variscides of Belgium and northern France

The origin, geochemistry and migration patterns of palaeofluids during an o rogeny have been investigated at the Variscan front zone in Belgium and nor thern France. A review has been made of four structural, mineralogical and geochemical studies of Variscan vein systems. The comparison of these case studies shows that open versus closed fluid how systems active during compr essional deformation can be distinguished based on the data acquired. Howev er, a detailed knowledge of the basin and of its diagenetic and tectonic ev olution is necessary to determine the origin and migration pattern of the a ncient fluids. This prerequisite partly restricts the predictability of the characteristics of the palaeofluids and the migration systems. (C) 2000 El sevier Science B.V. All rights reserved.