Resumen de Las mineralizaciones auríferas de los Pirineos y su significado en la evolución del orógeno Hercínico.
Albert Soler i Gil, Esteve Cardellach i López, D. Arcos Bosch, Joaquín Delgado Rodríguez
Gold is found in the Hercynian terranes of Central and Eastern Pyrenees as disseminations in metasediments of lower Paleozoic age; in veins contemporaneous with the main Hercynian foliation; in veins related to the Hercynian shear zones, faults and thrusts that postdate the main foliation and in skarns related to late Hercynian granites. Gold is associated to arsenopyrite, a typical feature throughout the Pyrenees. Two types of mineralizing fluid have been recognized: a CO2- rich low salinity (6% wt NaCI eq.) fluid, present in the synfoliation veins and a CO2- free and high salinity (up to 30% wt NaCI eq) fluid found in the post-foliation deposits. Ore deposition took place around 500 ºC and 5kb in the synfoliation veins and around 350 ºC and 2kb in the post-foliation veins and skarns. The late Hercynian uplift of themetamorphic terranes caused a steep rise in the thermal gradient (from 25 to 50ºC/km), theexpansion of porous fluid, and its migration into faults and thrusts. In the case of the skarns, the fluids were mobilized because of the thermal gradient related to the contact metamorphism.
