Rio Tinto (ES)

Other Names: Cerro Colorado, Atalaya, Filon Norte, Planes, San Dionisio
District: Iberian Pyrite Belt
Commodities :   Copper, Gold, Lead, Silver, Zinc

The Rio Tinto group of orebodies and mines occupies an area approximately 4 x 2 km in size, to the north of the town of Rio Tinto, approximately 65 km NE of Huelva in south-west Spain. It has a 4000 year history of mining. Large scale operations commencing in 1873 were carried out by the British-owned Rio Tinto Company until, in 1954, they sold their properties to mostly Spanish owners. The mines closed in 2003. Some orebodies (e.g. Au-Ag gossans) were by that time exhausted; others (e.g. VMS & stockworks) were unprofitable at going metal prices. A large resource remains in the ground. Cerro Colorado was originally a low hill capped by a prominent ferruginous gossan, located 2 km NE from the township of Rio Tinto, in the core of the Rio Tinto anticline. The gossan formed in-situ, partly on remnants of an erosion-dissected massive pyritite lens, and partly on footwall stockwork. It was up to 40 m thick, and the modern mined resource has been estimated at ~8 Mt @ 50 g/t Ag, 2.8 g/t Au; however, the amount removed is not known and the resource is now completely exhausted. The greatest precious metal enrichment occurs at the base, in the presence of jarosite. The shape of the stockwork ore zone is cylindrical, and its surface dimensions are 2200 x 1000 m with a thickness of at least 450 m. The pre-mining reserve of ~200 Mt of ore @0.43% Cu, 0.1 g/t Au was contained in an overall resource of some 1,500 Mt of low-grade material carrying 0.15% Cu, 0.15% Zn, 7 g/t Ag, 0.07 g/t Au. Ore material consisted of a dense network of veinlets, stringers and disseminations of mainly pyrite, chalcopyrite and minor zinc/lead sulphides in intensely chlorite-altered (and at the fringe sericite-altered) felsic volcanics. 

February 2004