Fluids and Variscan Metallogenesis in Granite Related Systems in Portugal

Most of the fluids that migrated in the higher crust at the end of Variscan orogeny were modified waters that were mixed with surface water during the decrease of the P-T conditions. The crustal discontinuities, the emplacement of the granitic rocks, the uplift and general decompression of the Variscan units were the main driving forces for this migration. In Iberian province some of the granites played also an important role in the ore forming processes supplying heat to drive the mineralizing system rather than being the source of fluids or metals. The existence of magmatic fluids although likely was never of importance, leaving practically no evidence of their existence in the fluid inclusion record. This is in contrast with large batholiths dominating other Sn-W provinces of the Variscan Belt such as the Cornubian and Erzegebirge where granites supplied significant amounts of fluid for the mineralizing process.