Secondary jarosite and water-soluble iron-sulfate minerals control the composition of acid mine waters formed by the oxidation of sulfide in tailings impoundments at the (Zn-Pb-Ag) Pan de Azúcar mine located in the Pozuelos Lagoon Basin (semi-arid climate) in Northwest (NW) Argentina. In the primary zone of the tailings (9.5 wt % pyrite-marcasite) precipitation of anglesite (PbSO₄), wupatkite ((Co,Mg,Ni)Al₂(SO₄)₄) and gypsum retain Pb, Co and Ca, while mainly Fe²⁺, Zn²⁺, Al³⁺, Mg²⁺, As^3+/5+ and Cd²⁺ migrate downwards, forming a sulfate and metal-rich plume. In the oxidation zone, jarosite (MFe₃(TO₄)₂(OH)₆) is the main secondary Fe³⁺ phase; its most suitable composition is M = K⁺, Na⁺, and Pb²⁺and TO₄ = SO₄²⁻; AsO₄²⁻. During the dry season, iron-sulfate salts precipitate by capillary transport on the tailings and at the foot of DC2 (tailings impoundment DC2) tailings dam where an acid, Fe²⁺ rich plume outcrops. The most abundant compounds in the acid mine drainage (AMD) are SO₄²⁻, Fe²⁺, Fe³⁺, Zn²⁺, Al³⁺, Mg²⁺, Cu²⁺, As^3+/5+, Cd²⁺. These show peak concentrations at the beginning of the wet season, when the soluble salts and jarosite dissolve. The formation of soluble sulfate salts during the dry season and dilution during the wet season conform an annual cycle of rapid metals and acidity transference from the tailings to the downstream environment.

Variações dos isótopos de C e Sr em carbonatos pré e pós-glaciação Jequitaí (Esturtiano) na região de Bezerra-Formosa, Goiás

Geologia e ocorrências de ouro do Terreno Granito-Greenstone do Tocantins, TO: síntese do conhecimento e parâmetros para exploração mineral

Ultramafic (UM) rocks are defined as igneous rocks that contain more than 90% of mafic minerals. Soils derived from ultramafic rock are generally nutrient-deficient and have concomitant high concentrations of potentially phytotoxic trace elements (Ni, Cr, Co, Mn). Consequently, to assess the dynamics of nutrients and metals in the ultramafic complex of Niquelândia (Brazil), soil solutions have been sampled in soils characterized by high Cr(VI) availability. The metal contents in surficial water have also been analyzed to investigate the metals’ leaching and mobility. Soil solutions featured low nutrient contents, a large Ca:Mg imbalance, and high Ni and Cr concentrations. Chromium was present in its toxic dissolved form (Cr(VI)) in the soil and surficial solutions. Metals concentrations were often above the toxic limit for biota and were therefore able to affect soil functioning. Ni behavior in the topsoil appeared to be primarily controlled by organic matter, while Cr was more likely to be released from Fe-oxides by anionic exchange. This result agreed with the Cr(VI) lability assessed using isotopic exchange kinetics in a companion study. In these serpentinic tropical soils, the highly leached Fe-oxide horizons appear to play a large role in the sequestration and diffuse leaching of labile Cr(VI) and Ni, respectively, in the deeper part of soil profiles and the topsoil. At the catchment scale, surficial solutions results suggest that metals may be exported to surrounding ecosystems that are not adapted to these metals.