Geochemistry in the Uranium bearing minerals of the Vale da Abrutiga Mine (Central Portugal)

Abstract

P a l a v r a sc h a v e : m ineralização de urânio, fo sfa to s secundários de urânio, Portugal. K ey w o r d s : uranium mineralization, secondary uranium phosphates, Portugal. R e su m oA antiga mina do Vale de Abrutiga está localizada na região central de Portugal. N esta região, o granito de grão grosseiro a muito grosseiro, porfiróide, biotítico, peralu m in o so de 308 ± 11 Ma in tru íu o C om plexo X isto -M etagrauváquico Câmbrico. O granito contém 10 ppm de U e uraninite primária, e foi, provavelmente, a fonte de U da m ineralização, que ocorre essencialmente em filonetes de quartzo, os quais intersectam o Complexo Xisto-metagrauváquico, mas também a impregnar indistintamente o filito adjacente a estes filões. Os filonetes de quartzo mineralizados estão brechificados e preenchem falhas com orientação N10°W, 8 0 Έ , as quais intersectam veios de quartzo mais antigos, de direcção NW-SE. O jazigo é do tipo dissem inado, ocorrendo a m ineralização na zona superficial, alterada. O m inério de urânio foi explorado a céu aberto, com um teor de 1 Kg UsOg/ton. A m inerali zação é formada por fosfatos secundários de urânio: saleíte, meta-saleíte e Fe-saleíte. Os filonetes de quartzo contêm, também, outras fases portadoras de urânio, como por exemplo oxi-hidróxidos de Fe, zircão, xenotima, monazite, anatase, moscovite e clorite. De um modo geral os minerais portadores de urânio apresentam os bordos mais ricos em urânio do que os seus núcleos.

Contaminated water, stream sediments and soils close to the abandoned Pinhal do Souto uranium mine, central Portugal

“…These correlations in stream sediments reflect the capacity of Fe-oxyhydroxides to adsorb metals and metalloids in the surface environment (e.g. Abdelouas, 2006;Cabral Pinto et al, 2008;Carvalho et al, 2012;Grosbois et al, 2007;Root et al, 2007) and indicate the influence of mine dumps, because the stream sediments receiving the direct drainage from these mine dumps have the highest concentrations of Fe, As, Cd, Cr, Pb and Th (Table 3). (Portuguese Decrees, 1998, 2007, except for U (WHO, 2010).…”

“…In the stream sediments, Fe-oxides precipitate (PS-SED5) is the main carrier of Fe, As, Cd, Co, Sr, Th, U and W (Table 3), because it immobilises metals and metalloids adsorbed onto the surfaces of Fe-oxyhydroxides (e.g. Cabral Pinto et al, 2008;Carvalho et al, 2012;Frau and Ardau, 2004;Grosbois et al, 2007;Pinto et al, 2004) and some is retained in organic matter. Variations in pH and Eh or a flood event can cause dissolution of these Fe-oxyhydroxides and thus release high amounts of toxic metals and metalloids into the environment (Carvalho et al, 2012;Siegel, 2002).…”

“…The high uranium concentration of up to 71.85 μg/l in the water sample (PS7) from upstream of the mine influence suggests that the country granite contains uranium. The Variscan two-mica granite from the Pinhal do Souto uranium mine, which is cut by the mineralised quartz vein, has a mean 10 ppm U concentration (Silva and Neiva, 2000) and contains uraninite (Cabral Pinto et al, 2008. This granite belongs to the Beira batholith, which contains uranium minerals (Cotelo Neiva, 2003) and is an important source of uranium for surface water and groundwater (Porcelli et al, 1997).…”

“…The Al content was used for normalisation, as Al is almost immobile in the surface environment. The average of each element from the five regional stream sediment samples collected in the Pinhal do Souto uranium mine area (Table 3) was used as a baseline value, because background values depend on the scale and lithology and the use of background values obtained in large areas consisting of several lithological Pinto et al (2004), Cabral Pinto et al (2008 Waters and stream sediment samples are downstream the uranium mines and dumps. *below the detection limit.…”

Experimental and Theoretical Studies on the Adsorption Mechanisms of Uranium (VI) Ions on Chitosan

“…Although these features are advantages, it is very important to remember that U is a harmful pollutant in the natural environment. In particular, it has been pointed out that the mining and milling of U minerals generates a large amount of waste materials (tailings), which lead to environmental health damage [ 2 , 3 , 4 , 5 , 6 , 7 ]. To solve these problems, the proper management of U tailings by phytoremediation has been implemented recently [ 2 , 3 ].…”