Limestone can be an option for sulfate sorption, particularly from neutral mine drainages because calcium ions on the solid surface can bind sulfate ions. This work investigated sulfate removal from mine waters through sorption on limestone. Continuous stirred-tank experiments reduced the sulfate concentration from 588.0mg/L to 87.0mg/L at a 210-min residence time. Batch equilibrium tests showed that sulfate loading on limestone can be described by the Langmuir isotherm, with a maximum loading of 23.7mg/g. Fixed-bed experiments were utilized to produce breakthrough curves at different bed depths. The Bed Depth Service Time (BDST) model was applied, and it indicated sulfate loadings of up to 20.0gSO(4)(2-)/L-bed as the flow rate increased from 1 to 10mL/min. Thomas, Yoon-Nelson and dose-response models, predicted a maximum particle loading of 19mg/g. Infrared spectrometry indicated the presence of sulfate ions on the limestone surface. Sulfate sorption on limestone seems to be an alternative to treating mine waters with sulfate concentrations below the 1200-2000mg/L range, where lime precipitation is not effective. In addition, this approach does not require alkaline pH values, as in the ettringite process.

ABSTRACT:Mapping methods for iron oxides and clay minerals, using Landsat-8/Operational Land Imager (OLI) and Earth Observing 1 (EO-1)/Hyperion imagery integrated with airborne geophysical data, were applied in the N4, N5, and N4WS iron deposits, Serra Norte, Carajás, Brazil. Band ratios were achieved on Landsat-8/ OLI imagery, allowing the recognition of the main minerals from iron deposits. The Landsat-8/OLI imagery showed a robust performance for iron oxide exploration, even in vegetated shrub areas. Feature extraction and Spectral Angle Mapper hyperspectral classification methods were carried out on EO-1/Hyperion imagery with good results for mapping high-grade iron ore, the hematite-goethite ratio, and clay minerals from regolith. The EO-1/Hyperion imagery proved an excellent tool for fast remote mineral mapping in openpit areas, as well as mapping waste and tailing disposal facilities. An unsupervised classification was carried out on a data set consisting of EO-1/Hyperion visible near-infrared 74 bands, Landsat-8/OLIderived Normalized Difference Vegetation Index, Laser Imaging Detection and Ranging-derived Digital Terrain Model, and high-resolution airborne geophysical data (gamma ray spectrometry, Tzz component of gradiometric gravimetry data). This multisource classification proved to be an adequate alternative for mapping iron oxides in vegetated shrub areas and to enhance the geology of the regolith and mineralized areas. KEYWORDS:Remote sensing; Multispectral and hyperspectral imagery; Iron ore. RESUMO: Métodos de mapeamento para óxidos de ferro e argilas, aplicados em imagens Landsat-8/Operational Land Imager (OLI) e Earth Observing 1 (EO-1)/Hyperion e integrados com dados aerogeofísicos, foram testados nos depósitos de ferro de N4, N5 e N4WS, Serra

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Manganese removal from mining-affected waters is an important challenge for the mining industry. Addressed herein is this issue in both batch and continuous conditions. Batch experiments were carried out with synthetic solutions, at 23+/-2 degrees C, initial pH 5.5 and 8.3 g limestone/L. Similarly, continuous tests were performed with a 16.5 mg/L Mn(2+) mine water, at 23 degrees C, initial pH 8.0 and 20.8 g limestone/L. Calcite limestone gave the best results and its fine grinding proved to the most effective parameter for manganese removal. In either synthetic solutions or industrial effluents, the final manganese concentration was below 1 mg/L. A change in limestone surface zeta potential is observed after manganese removal and manganese carbonate formation was suggested by IR spectroscopy. The conclusion is that limestone can remove manganese from industrial effluents for values that comply with environmental regulations.

Mafic dikes are abundant in the Quadrilátero Ferrífero and Southern Espinhaço regions, southeastern State of Minas Gerais. The dikes range from 1,7 Ga to 120 Ma and form at least three swarms that differ in trend, mineralogy, composition and age. The oldest swarnrhas a baddeleyite U/Pb age of 1,7 Ga (Ibirité Gabbro) and K-Ar age of about 1 ,7-1 ,5 Ga (schists), trends north-south, the dikes vary in width from centimeters to meters, and are deformed and metamorphosed to cnlorite-sericke-quartz-plagioclase schist or are some meters wide and contain plagioclase, augite,-ilmenite, quartz and traces of baddeleyite. These dikes are enriched in LREE [(La/Sm)N =3,68-6.39], and depleted to enriched in HREE [(Dy/Yb)N = 0,82-1,29]. These dikes (and sills also) are related to the opening of the Espinhaço Basin. Nprthwest-and northeast-trending mafic dikes have a U/Pb age of about 906 Ma. They are commonly ten meters wide, and are of metagabbro with relict igneous textures and containing altered plagioclase (Ans-52), amphibole, epidote, ilmenite, quartz, and apatite. Samples of this dike swarm are slightly enriched in LREE and HREE with a (La/Sm)N = 1 .32 to 2.2 and (Dy/Yb)N = 1 .36 to 1 .88, respectively, and also show small negative europium anomaly. Sills, stocks, plugs, laccoliths and phaccoliths with compositions similar to dikes are present in the study area. The Sm-Nd data indicate negative ENU (T) (+ 1 .34 and-3.20) and model ages (T DM) of ca. 2.59 and 1 .35 Ga. These dikes may be related the first stages of the Panafrican/Brasiliano event. North-south, east-west, northwest and northeast trending Phanerozoic dikes are of diabase composed of plagioclase (An«)), augite and magnetite. They show moderate LREE (La/Sm)N = 2,53, and slight HREE enrichments, (Dy/Yb)N = 1,47. These dikes have a K/Ar age of about 120 Ma and may be related to the fragmentation of Gondwanaland. The Quadrilátero Ferrífero and Southern Espinhaço dikes are tholeitic and exhibit prominent iron-enrichment. Some trace element distributions are similar to continental rift basalts. They represent significant amounts of mafic melts formed during the beginning of ample extensional tectonic regimes. There are significant variations in incompatible and partially compatible element abundances both within and between dike swarms, which is due not only to heterogeneous mantle sources, but also to crustal contamination. RESUMO ENXAMES DE DIQUES MÁFICOS DO QUADRILÁTERO FERRÍFERO E ESPINHAÇO MERIDIONAL, MINAS GERAIS, BRASIL Enxames de diques máficos são abundantes no Quadrilátero Ferrífero Quadrilátero Ferrífero e Espinhaço Meridional, sudeste de Minas Gerais. Três eventos de magmatismo básico ocorrem nestas regiões, cada qual com feições estruturais, petrográficas, geoquímicas e geocronológicas próprias. O enxame mais antigo tem idade de 1,7-1,5 Ga (U/P badeleíta-Ibirité Gabbro e K-Ar RT-xistos) e ocorre como sills e diques de direção NS, deformados e metamorfisados, ou como diques não deformados com a textura ignea preservada. Os deformados são clorita-sericita...