Geoquímica y origen de los fluidos asociados a los yacimientos de fluorita de "Berbes-La Cabaña" y "La Collada" (Asturias)

Abstract

This study evaluates a-CI-Br systematic of fluid inclusions in fluorites from "Berbes-La Cabaña" and "La Collada" districts in Asturias (N of Spain). The fluorites were formed as H20-NaCI-Ca2CI fluids represented by primary inclusions (Lwl) showing moderate salinity (Tm:-l 2.4° to -6.6°C) and homogenization temperature between 130° to 150°C. Lw2 inclusions are secondary with low salinity (Tm:-2.9 to -2.7°C) and global homogenization ranging between 130° to 135°C. Hypersaline Lw-s inclusions have distinguished in La Collada district. The high salinity of these inclusions could be explained as resulting of reequilibration processes. Comparison ofNa-CI-Br compositions show fundamental differences in halogen chemistry between two regions. Crush-leach extraction ana chemical analysis of the inclusions from "Berbes-La Cabaña fluorites reveals that the fluid chemistry is influenced by the fluid-rock interaction with Na-Ca exchange. The low concentration of Br suggest a brine derived from halite dissolution by reaction with evaporites. In contrast, Cl/ Br and Na/Br decrease strongly In brines from "La Collada" fluorites and are similar to modern seawater. These halogen ratios are consistent with solutes derived from evaporation of seawater.