Geology and mineralogy of the Linares area, a new gold mineralization in the Navelgas Gold Belt, western Asturias, Spain

摘要

The Linares granites (Navelgas Gold Belt) are located in the Narcea Antiform, a zone between the Cantabrian and the Asturian-Leonese Zones of the Iberian Massif. Several outcrops and two different granite facies, porphyritic and equigranular, are observed. Both are monzogranites with high K-content and light peraluminous character. Geochronological data (K-Ar in biotites) give an age of 290~(+-)6 Ma for the porphyritic and 276~(+-)6Ma for the equigranular. Hydrothermalism and sulfide-gold mineralization in the porphyritic intrusions are characterized by a propylitic alteration from a stockwork of quartz veins several centimetres wide. The equigranular granite presents a disseminated mineralization together with strong potassic alteration and silicification. In both cases, pyrrhotite, chalcopyrite and arsenopyrite are the most abundant metallic minerals and pyrite, sphalerite and loellingite are also present. Native gold accompanies bismuth and tellurium minerals, which occupy fractures, above all in arsenopyrite and, occasionally, in chalcopyrite.