Las mineralizaciones de barita de Cerro del Hierro (Sevilla). Características mineralógicas y geoquímica

Abstract

Different barite deposits (stratabound, vein and karstic types) are occurring in the Lower Cambrian carbonatic materials of the Cerro del Hierro, Sevilla (Ossa-Morena Zone). Calcite, hematite, goethite and minor chalcopyrite are common associated minerals, with limonite and malachite as alterations. The content of barite can be as high as 98 %. There is a close relationship between barite type and Sr content (vein < stratabound < karstic deposits). δ₃₄S ranges between 32,7 ‰ (stratiform barites) and 20,7 ‰ (epigenetic barites). The ⁸⁷Sr/⁸⁶Sr ratio for the epigenetic barites oscillates between 0.70873 and 0.71112 which could be the result of the infiuence of different mineralization solutions. A primary origin for the stratabound barites is proposed, in relation with the diagenesis of the limestones occurred during the Lower Cambrian. Epigenetic barites were formed after the Hercynian Orogenesis by remobilization of the stratiform ores, with Ba and Sr supplied from the lixiviation of the host rocks. The last process could be much more important for the karstic barite formation.