Mineralogical and geochemical characterization of gold mining tailings and their potential to generate acid mine drainage (Minas Gerais, Brazil)

• Published in: Minerals (Basel) Vol. 11; no. 1; pp. 1 - 16
• Main Authors: Lemos, Mariana, Valente, Teresa Maria Fernandes, Marinho Reis, A. Paula, Fonseca, Rita, Delbem, Itamar, Ventura, Juliana, Magalhães, Marcus
• Format: Journal Article
• Language: English
• Published: Basel MDPI 01.01.2021; MDPI AG
• Subjects: Acid mine drainage; Aluminum; Anniversaries; Antimony; Brazil; Carbonates; Chromium; Circuits; Ciências da Terra e do Ambiente; Ciências Naturais; Copper; Cyanides; Deactivation; Flotation; Geochemistry; Geochemistry and environmental mineralogy; Gold; Gold ores; Grain size; Iron; Leaching; Magnesium; Manganese; Mercury; Metallurgy; Minas Gerais— Minas Gerais—Brazil; Mine drainage; Mine tailings; Mine wastes; Mineral processing; Mineralogy; Minerals; Mining; Mobility of toxic elements; Nickel; Ores; Oxidation; Oxides; Proteger a vida terrestre; Pyrite; Pyrrhotite; Science & Technology; Selenium; Silicates; Sulfides; Sulphides; Tailings; Temperature; Waste materials; Wastes; Water pollution; Zinc; Brazil; United States > US
• ISSN: 2075-163X; 2075-163X
• DOI: 10.3390/min11010039

For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings from an ongoing plant, were studied for their acid mine drainage potential and elements’ mobility. Detailed characterization of both tailings types indicates the presence of fine-grain size material hosting substantial amounts of sulfides that exhibit distinct geochemical and mineralogical characteristics. The samples from the ongoing plant show high grades of Fe in the form of oxides, cyanide, and sulfates. Differently, samples from the old circuit shave higher average concentrations of Al (0.88%), Ca (2.4%), Mg (0.96%), and Mn (0.17%), present as silicates and carbonates. These samples also show relics of preserved sulfides, such as pyrite and pyrrhotite. Concentrations of Zn, Cu, Au, and As are higher in the tailings of the ongoing circuit, while Cr and Hg stand out in the tailings of the deactivated circuit. Although the obtained results show that the sulfide wastes do not tend to generate acid mine drainage, leaching tests indicate the possibility of mobilization of toxic elements, namely As and Mn in the old circuit, and Sb, As, Fe, Ni, and Se in the tailings of the plant that still works. This work highlights the need for proper management and control of tailing dams even in alkaline drainage environments such as the one of the Cocoruto dam. Furthermore, strong knowledge of the tailings’ dynamics in terms of geochemistry and mineralogy would be pivotal to support long-term decisions on wastes management and disposal. This work was funded by FCT—Fundação para a Ciência e a Tecnologia through projects UIDB/04683/2020 e UIDP/04683/2020 and Nano-MINENV 029259 (PTDC/CTA-AMB/29259/2017, and by AngloGold Ashanti Brazil.