Prediction of leachate quality for a gossan dump, Angostura, Spain

Abstract

The Iberian Pyrite Belt (IPB) is one of the largest of the world’s massive sulfide provinces. Since the Chalcolithic era, gossans formed from massive sulfide mineralization have been worked for copper, silver and gold. Consequently many historical mine sites have abandoned dumps of gossanous material. One such example is located at Angostura, a historical copper mine which operated from 1906 to 1931. The aims of this study are to determine the mineralogical hosts of environmentally significant elements (As, Ba, Bi, Co, Cu, Hg, Mo, Sb, Se, Ni, Pb, Zn) in gossanous waste rocks dumped adjacent to the Angostura open cut, using geochemical, optical, SEM-MLA and laser ablation techniques. Our findings demonstrate that the gossan materials are enriched in environmentally significant elements with several hosted by iron oxides and iron-oxyhydroxides. Leaching of these gossan materials was performed using three extractants to represent different conditions which may be experienced in a surficial environment (i.e., deionized water, hydrogen peroxide and sulfuric acid). Results from these experiments indicated that under ambient surface conditions all analyzed elements will not be released from their goethite and hematite hosts. However, under ARD conditions, elements such Co, Cu, Pb and Zn will be mobilized.