Indium in the Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal

The Iberian Pyrite Belt (IPB) is one of the most outstanding ore provinces in Europe hosting some of the largest concentrations of massive sulphides and 22% of the world-class (>32 Mt) VMS orebodies. A significant number of (pyrite) mines are now inactive but some orebodies still remain unexploited; this is the case of Lagoa Salgada. It is the most NW orebody known and occurs beneath approximately 130 m of Cenozoic sediments which limits interpretation solely to borehole intersection data. The orebody is folded and interpreted to occur on the subvertical-overturned and intensely faulted limb of a SW verging anticline. It is hosted within a thick IPB volcanic sedimentary sequence and is made up of a central stockwork and a massive sulphide lens. An electron microprobe study revealed consistent trace amounts of indium in sphalerite, thus contrasting with the neighbouring Neves Corvo mine where indium is known to occur associated with stannite and stanoidite. The occurrence of elevated trace amounts of indium in sphalerite from Lagoa Salgada could make this orebody an attractive economic target beyond the traditional tin base metal suite so far extracted in the Iberian Pyrite Belt.