ABSTRACT
The studied deposits belong to the “Bielsa district” and are located in the Axial Zone of the Spanish Central Pyrenees. They consist of E-W trending F-(Pb-Zn) veins, hosted by the granodioritic Bielsa batholith and the lower Triassic red-beds. Primary deposition of the lodes should have occurred after cooling of low fractionated fluids derived from the Hercynian basement, as REE+Y data suggest. Structural and textural observations, together with microthermometrical analysis of fluid inclusion planes (FIP) indicate that veins were strongly sheared during the Alpine orogeny, involving Triassic fluids.
