The different fluid percolations in the granitic complex of Saint-Sylvestre (Northwest French Massif Central) at the end of the Hercynian orogeny is relatively well described in the mining area, but their extension is unknown at the scale of the whole massif. Microthermometric and microstructural studies, outside any mineralized zone, show that different fluids circulated among three sets of microfissures: i) aqueous-carbonic fluids (N40 o E and N150 o E), ii) aqueous vapours and liquids (east-west) similar to those considered as linked to the granite episyenitisation, and iii) low temperature aqueous fluids (east-west). The first event is characterized by high temperatures at rather low pressures, indicating a high geothermal gradient (80-90 o C.km - 1 ) similar to those observed in the proximity of intrusions in the present-day geothermal field. It confirms the close space-time relationships between the migration of these aqueous-carbonic fluids and the Late Hercynian granites intruding the Saint-Sylvestre massif some kilometers southwards. Other fluid events, attesting a cooling of more than 200 o C after the previous fluid stages, seem to be related to the incoming of meteoric fluids in the system, followed by local fluid immiscibility and cooling. These processes are common features of geothermal areas.La percolation de differents types de fluides dans le complexe de Saint-Sylvestre (Nord-Ouest du Massif central), a la fin de l'orogenese Hercynienne, est assez bien decrite dans les secteurs mineralises et/ou alteres, mais leur extension a l'echelle du massif reste peu connue. Les etudes microstructurales et microthermometriques, realisees hors contexte mineralise, montrent que differents fluides percolent selon trois orientations de microfissures : (i) fluides aquo-carboniques (N40 o E et N150 o E), (ii) fluides aqueux vapeurs et liquides (est-ouest) similaires a ceux responsables de l'episyenitisation, (iii) fluides aqueux de faible temperature (egalement est-ouest). Le premier evenement est caracterise par des temperatures elevees (450 o C), pour des pressions relativement faibles, indiquant un fort gradient geothermique (80-90 o C.km - 1 ), similaire a ceux observes a proximite d'intrusions dans les champs geothermiques actuels. Il confirme l'etroite relation espace-temps entre la migration de ces fluides aquo-carboniques et les granites tardifs intrudant le massif de Saint-Sylvestre. Les autres evenements fluides, attestant un refroidissement de plus de 200 o C, semblent etre lies a la venue de fluides meteoriques dans le systeme, suivie par une immiscibilite locale des fluides, et a un refroidissement, processus commun des systemes geothermiques.