Hydrothermal alteration in the Linares-La Carolina Ba-Pb-Zn-Cu-(Ag) vein district, Spain: mineralogical data from El Cobre vein

Abstract

The Linares–La Carolina Ba–Pb–Zn–Cu–(Ag) vein deposits, Spain (Fig. 1), which were developed principally in the period 1875–1920, constituted one of the most outstanding mining districts of Europe, with an average lead production of 65 000 t/year and up to 500 g/t silver obtained as a by-product. The workings were concentrated on vein-type hydrothermal mineralization hosted by granitoids and metasediments. The El Cobre vein, a cordilleran vein-type deposit (sensu Gilbert and Park7), is representative of the veins in the district and is also one of the largest. It strikes northeast–southwest for about 5 km, has an average thickness of 2–3 m and is hosted by monzogranitic rocks (the so-called Monzogranito de Linares) and minor Carboniferous metasediments. The Linares monzogranite belongs to the Los Pedroches batholith—a large, late-Hercynian (312–308 m.y.)4,5 intrusive unit comprising granodiorites, monzogranites, tonalites, diorites and quartzdiorites.8,11 The Linares monzogranite is a mediumto coarse-grained, moderately peraluminous rock consisting of quartz (25–30 vol%), plagioclase (25–45 vol%; An34 and albite-rich An12–6), K-feldspar (10–30 vol%; Or97–93 Ab3–7) and biotite (4–11 vol%; AlVI = 0.21–0.18 atoms per formula unit). Pseudo-primary muscovite is very rare. The El Cobre vein records three stages of mineralization, which were separated by major brecciation events (Fig. 2). The first stage was characterized by deposition of quartz and