A typological classification of Spanish precious metals deposits

• Autores: Ricardo Martínez Castroviejo
• Localización: Cadernos do Laboratorio Xeolóxico de Laxe: Revista de xeoloxía galega e do hercínico peninsular, ISSN 0213-4497, Nº 20, 1995, págs. 253-279
• Idioma: inglés
• Títulos paralelos:
  • Clasificación tipológica de los yacimientos españoles de metales nobles
• Enlaces
  • Texto completo
• Resumen

  • Last decade's intensive exploration for precious metals in Spain led to a new understanding of various types of deposits and prospects. A summary review of recent progress is presented, allowing the systematic (typological) classification of the Spanish precious metals deposits shown in Table 1: 19 types are defined in the framework of the Iberian Geology, their exploration significance being also considered. Hypogene deposits in the Hercynian Hesperian Massif, and epithermal gold deposits in the Neogene calc-alcaline Volcanic Province of SE Spain have been very much explored and are therefore emphasized, although their mining production is by far not to compare with the precious metals output the SWIPB (SW Iberian Pyrite Belt).

    In the Hesperian Massif, different metallotects have been demonstrated to be related to attractive concentrations of gold, bound to Hercynian shear-zones, in Galicia, in Extremadura, etc.; other concentrations (e. g., in Galicia and Asturias) are related to granite or porphyry intrusions (Salave) and skarn formations (Carlés). PGE or Platinum elements (± chromite) have been found in ophiolitic thrust complexes occurring in N Galicia, e. g. the Herbeira Massif of the Cabo Ortegal Complex, as had been in the 1940's in Northern Portugal (Bragança and Morais complexes). Exploration for silver has demonstrated a small orebody in Fuenteheridos (Aracena, SW Spain), not minable under severe environmental constraints, but none of the classic Spanish silver producing districs (vein-Type deposits, e. g. Guadalcanal or Hiendelaencina) has recovered activity.

    Most of the EU (European Union) gold and silver production is won from only two types of deposits in the Spanish Hesperian Massif: the masive sulphides of the SWIPB, in which precious metals are won as by-products, and the related gossan deposits.

    In the Alpine domains, the SE Spanish volcanic region (Almería-Murcia), has for centuries been worked for Pb-Ag-Zn-(Cu) and for Sn (Fe) and is presently well know for its epithermal gold and silver mineralizations (e. g. Rodalquilar and Transacción mines, Almería), but its full potential has yet to be realized. Recent work has shown epithermal precious metal-bearing bodies to occur in an area spreading over one hundred Km. northwards from those mines, and demonstrated the feasibility of their detection by remote sensing. Sediment-hosted epithermal deposits have not yet been found in the region, but are not to be excluded. An attractive, possibly economic, base metal and silver prospect is under investigation near Mazarrón (Murcia). In another context, the ultramafic massifs of the Serranía de Ronda (Málaga) are know as PGE metallotects, in which a new type of PGE mineralization has been recently defined. On the other hand, exploration for gold in the Hercynian Basement of Alpine domains has also shown interesting prospects to occur, as in the pyreneean Vall de Ribes district.

    Finally, the formerly very important detrital (paleo-placer and placer) gold concentrations of Neogene to Quaternary age, occurring mainly in NW Spain although explored by various companies, did not lead to any mining activity yet. The overall picture of these years of research is an increased knowledge of the Spanish precious metals ore geology, the full reconnaissance and higher mining production of the gossan bodies of the SWIPB and the development of several prospects (Carlés-Salas, Salave, Fuenteheridos, Mazarrón, etc.) and of a gold mine (Transacción, Almería, of ephemeral activity). On the other hand, sorne questions have arisen which define interesting goals for future research, as the precise models of the different types of shear-zone orebodies, the evolution at depth of the Au-Ag orebodies in the known epithermal districts (e. g. Cabo de Gata, Almería), and the regional extent and exploration of thes.e orebodies (partly, under metamorphic and sedimentary Hercynian formations) in the SE Spain Neogene volcanic province, as well as the possible existence of disseminated, sediment-hosted Carlin-Type ore bodies.