The Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal

The Iberian Pyrite Belt is one of the most outstanding European ore provinces and hosts one of the largest concentrations of massive sulfide deposits today, totaling 1,850 million metric tons (Mt) in more than 90 deposits. Lagoa Salgada is a small orebody (estimated to have at least 4 Mt) and, as yet, an unexploited orebody found within this ore province. It is located 80 km northwest of Neves Corvo and occurs ~130 m beneath sediments of the Sado Tertiary basin, limiting interpretation to drill hole data. Lagoa Salgada is folded, faulted, and interpreted to occur mostly on the subvertical-overturned and intensely faulted limb of a southwest-verging anticline. It is represented by a central stockwork zone and a massive sulfide lens zone in the northwestern part of the orebody. Mineralization is mainly composed of pyrite with minor sphalerite, tetrahedrite-tennantite, arsenopyrite, chalcopyrite, galena, stannite, and supergene minerals. The orebody is hosted by a volcanic succession of rhyodacitic composition. These small orebodies and some of the other abandoned mines within the Iberian Pyrite Belt may represent interesting and feasible mining projects as a result of the added value generated by the presence of trace metals, such as In, serving a significant future demand for the high-tech industry. Lagoa Salgada is one such case. Indium is a significant trace metal in the ores of Lagoa Salgada as indicated by whole-rock analyses. This element is preferentially contained by sphalerite. Electron probe microanalyses (EPMA) of In contents within sphalerite show a large variability, ranging from below detection limits to an obtained maximum of 0.8 percent In. Discrete inclusions of In-bearing minerals have not been observed, thus favoring the idea that In occurs either dispersed or in nanodomains within the host mineral.