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- 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 e petrologia dos granitos variscos sin-D3 da região de Santa Comba de Rossas, norte de PortugalPublication . Teixeira, R. J. S.; Gomes, Maria Elisa Preto; Silva, Paulo Bravo; Meireles, CarlosSUMMARY: In the Santa Comba de Rossas - Paredes area, a granitic complex (G1-G3) was emplaced during the syn-kinematic stages of the Variscan Orogeny, at 317.9 ± 8.7 Ma, as determined by whole rock Rb-Sr dating. The complex intruded Silurian metasediments, from the Parauthocthonous Domain of Galicia – Trás-os-Montes Zone, in a NW-SE trending antiform formed during the D1 and D3 deformation phases, but was itself affected by ductile and brittle deformation. Geochemical and isotopic characteristics suggest that the biotite > muscovite granite G1 and the biotite ≈ muscovite granite G2 correspond to distinct pulses of magma formed by partial melting of metasedimentary materials that subsequently evolved by fractional crystallization. This process was responsible for the increase in Sn content in those granites and, most probably, for the occurrence of the exocontact muscovite granite G3, which is the richest in Sn (77 ppm), due to a higher degree of fractional crystallization.