Browsing by Author "Antunes, I. Margarida H. Ribeiro"
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- Assessment of metal and metalloid contamination in soils trough compositional data: the old Mortórios uranium mine area, central PortugalPublication . Neiva, A.M.R.; Albuquerque, M.T.D.; Antunes, I. Margarida H. Ribeiro; Carvalho, P.C.S.; Santos, A. C. T.; Boente, C.; Cunha, Pedro Proença e; Henriques, S.B.A.; Pato, R. L.ABSTRACT: Soils from the old Mortórios uranium mine area were studied to look for contamination, as they are close to two villages, up to 3 km away, and used for agriculture. They are mainly contaminated in U and As and constitute an ecological threat. This study attempts to outline the degree to which soils have been affected by the old mining activities through the computation of significant hot clusters, Traditional geostatistical approaches commonly use raw data (concentrations) accepting that the analyzed elements represent the soil’s entirety. However, in geochemical studies these elements are just a fraction of the total soil composition. Thus, considering compositional data is pivotal. The spatial characterization, considering raw and compositional data together, allowed a broad discussion about not only the concentrations’ spatial distribution, but also a better understanding on the possibility of trends of “relative enrichment” and, furthermore an insight in U and As fate. The highest proportions (compositional data) on U (up to 33%), As (up to 35%) and Th (up to 13%) are reached in the south-southeast segment. However, the highest concentrations (raw data) occur in north and northwest of the studied area, pointing out to a “relative enrichment” toward the south-southeast zone. The Mondego Sul area is mainly contaminated in U and As, but also in Co, Cu, Pb and Sb. The Mortórios area is less contaminated than the Mondego Sul area.
- Assessment of metal and metalloid contamination in the waters and stream sediments around the abandoned uranium mine area from Mortórios, central PortugalPublication . Neiva, A.M.R.; Carvalho, P.C.S.; Antunes, I. Margarida H. Ribeiro; Albuquerque, M.T.D.; Santos, A.C.S.; Cunha, Pedro Proença e; Henriques, S.B.A.ABSTRACT: In the abandoned Mortórios uranium mine area there are quartz veins containing wolframite and sulphides and basic rock dykes with torbernite and autunite cutting a porphyritic granite. The basic rock dykes were exploited and produced about 27 t of U3O8, from 1982 to 1988. There are an open pit lake and nine dumps. Surface water and groundwater are contaminated in U, As, Cd, Cr, Cu, Fe, Mn, Ni and Pb. Stream sediments are contaminated in U, As, Th and W, which are adsorbed by smectite, kaolinite and iron- and aluminium- oxy-hydroxides. The maximum U concentrations are of 1268 μg/L in the open pit lake, 100 μg/L in surface water, 103 μg/L in groundwater and 81.5 mg/kg in stream sediments all downstream of the open pit lake and dumps. Further downstream the U concentration in water decreases, due to the high mobility of U (VI), but the U concentration in stream sediments increases. Calcium uranyl carbonate dominates in the open pit lake, but uranyl carbonate complexes dominate in surface water and gr oundwater. The maximum As concentrations are 56.0 μg/L in the open pit lake, 63.4 μg/L in the surface water and 66.7 μg/L in the groundwater, both downstream of the open pit lake and dumps. The arsenic occurs as As (V). The Mortórios area is compared with two other areas exploited from open pits, all located in the uranium-bearing Beira area of central Portugal. Vale de Abrutiga produced 90 t of U3O8 between 1982 and 1989 and Mondego Sul produced 75 t of U3O8 from 1987 to 1991. The two mines consist of quartz veins containing sulphides, saleeite and meta-saleeite at Vale de Abrutiga and with sulphides, autunite, torbernite, meta-uranocircite and meta-saleeite at Mondego Sul cutting the Schist-graywacke Complex. The mine area of Vale de Abrutiga with the highest exploitation of U3O8 has strongly acidic to slight alkaline water, which is the most contaminated. Mortórios with the lowest exploitation presents a higher contamination of slightly acidic to alkaline water than that of acidic to alkaline water from Mondego Sul, but the former has As (V), whereas the latter has As (III), which is toxic. The stream sediments from Mortórios present the lowest contamination, except for Th that has a higher median value than that from Vale de Abrutiga. Stream sediments from Mondego Sul have higher U, Th, Pb and lower Co, Cr, Cu and Zn median values than those of Vale de Abrutiga.
- Compositional trends in tourmalines from granites and quartz-tourmaline rocks from the Penamacor-Monsanto pluton (Eastern Central Portugal)Publication . Costa, Isabel Ribeiro da; Antunes, I. Margarida H. Ribeiro; Guimarães, Fernanda; Ramos, João Farinha; Recio, C.; Barriga, Fernando; Mourão, C.
- Geochemistry of minerals, waters and weathering from the Fonte Santa mine area, NE of PortugalPublication . Gomes, Maria Elisa Preto; Antunes, I. Margarida H. Ribeiro; Neiva, A.M.R.; Pacheco, F. A. L.; Silva, Paulo BravoThe quartz veins containing scheelite from Fonte Santa mine area were exploited for W between 1942 and 1982. At the end of November 2006, a flood event damaged the dam land of Fonte Santa mine and metal content of water increased. Fonte Santa mine area cuts the quartzites close to the Fonte Santa muscovite granite. The granite contains quartz, microcline, albite, muscovite, chlorite, columbite-tantalite, volframite, W-ixiolite and ilmenite. The quartz veins contain muscovite, chlorite, tourmaline, scheelite, pyrrhotite, pyrite, sphalerite, chalcopyrite, galena, arsenopyrite, magnetite, jarosite, phosphates of Pb, Fe and AI. The waters related to the Fonte Santa mine are poorly mineralized, with electrical conductivity < 965 ~S / cm, of mixed type or HCO3- and SO42- types. These waters have Fe and Mn contents that forbid to use that for human consumption and agriculture. Sodium, Mg and K water contents are associated with the alteration of albite, chlorite and muscovite of country rock, while Ca is related to the W-bearing quartz veins.
- Mineralogia dos filões aplito-pegmatíticos litiníferos da região de SeguraPublication . Antunes, I. Margarida H. Ribeiro; Neiva, A.M.R.; Silva, M. M. V. G.; Silva, Paulo BravoNa região de Segura, os filões aplito-pegmatíticos litiníferos Variscos intruíram o Complexo Xisto-Grauváquico, Câmbrico. Osfilões pegmatíticos são do tipo REL-Li e incluem-se na família dos pegmatitos LCT. A ocorrência de lepidolite, montebrasite, microlite, cassiterite e minerais do grupo da columbite primários sugerem um elevado grau de diferenciação nestes filões. A montebrasite primária é heterogénea e a lacroixite secundária ocorre nas suas zonas enriquecidas em Na. A cassietrite é zonada com alternância de zonas escuras e zonas claras e possui Mn > Fe, o que é raro. As zonas escuras são fortemente pleocróicas, com zonamento oscilatório, e possuem teores mais elevados de Nb e Ta do que as zonas claras. As inclusões de moscovite, apatite, ferrotapiolite, ixiolite e microlite foram encontradas em ambas as zonas de cassiterite, mas as exsoluções de ferrocolumbite, ferrocolumbite manganífera e manganocolumbite ocorrem nas zonas escuras.
- As rochas graníticas desde Castelo Branco a PortalegrePublication . Antunes, I. Margarida H. Ribeiro; Solá, A. Rita
- Transition metals responsible for striking colour variation in tourmalines : an EMP study of tourmalines from granites and quartz-tourmaline rocks associated to the Penamacor-Monsanto pluton (Eastern Central Portugal)Publication . Costa, Isabel Ribeiro da; Antunes, I. Margarida H. Ribeiro; Guimarães, Fernanda; Rodrigues, P. C. R.; Barriga, Fernando; Mourão, C.; Ramos, João Farinha; Hernandez, Récio
- Weathering and hydrochemistry associated with the old mine workings at Fonte Santa, NE of PortugalPublication . Gomes, M. Elisa Preto; Antunes, I. Margarida H. Ribeiro; Pacheco, F. A. L.; Neiva, A.M.R.; Silva, Paulo Bravo
- Weathering and hydrochemistry associated with the old mine workings at Fonte Santa, NE of PortugalPublication . Gomes, M. Elisa Preto; Antunes, I. Margarida H. Ribeiro; Pacheco, F. A. L.; Neiva, A.M.R.; Silva, Paulo Bravo