Browsing by Issue Date, starting with "2013-09"
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- The Juzbado-Penalva do Castelo wrench ductile shear zone : a major structure oblique to the main Iberian Variscan trendPublication . Pereira, Inês; Dias, Rui; Bento dos Santos, Telmo; Mata, João
- Resultados del proyecto GEMAS en la Península IbéricaPublication . Bel-Ian, A.; Locutura, Juan; Batista, Maria Joao; Martínez, S.
- Opportunities for recovering critical raw materials from mine wastes : the type-case of rhenium in residues from the exploitation of old portuguese minesPublication . Figueiredo, M. Ondina; Silva, Teresa; Batista, Maria Joao; Veiga, JP; de Oliveira, Daniel Pipa Soares
- Ascertaining the degradation state of ceramic tiles : a preliminary non-destructive step in view of conservation treatmentsPublication . Silva, Teresa; Figueiredo, M. Ondina; Prudêncio, Maria IsabelConserving the cultural heritage is a general concern and the use of non-destructive techniques to characterize ancient materials is important. Serious deterioration effects in environmentally exposed ancient glazed ceramic tiles arise from the development of micro-organisms (algae/fungi) within the pore system. Subsequent biodegradation processes are particularly harmful once the decorated glaze is damaged by exfoliation/detachment. Three case studies will be addressed: Portuguese polychrome decorated tiles from the interior of two churches (16th–17th century) and from the outdoor of a Palace (18th century). Small tile fragments were directly irradiated in a wavelength-dispersive X-ray fluorescence spectrometer for glaze chemical characterization and subsequently irradiated in a powder diffractometer to assess the phase constitution of both glaze and ceramic body. Cleaning and conserving these ancient cultural artifacts involve a decontamination process applying innovative non-destructive techniques. The present work is intended as a contribution to diagnose the actual degradation state of ancient tiles in view of future decontamination actions using gamma radiation.
- Molybdenite as a rhenium carrier : first results of a spectroscopic approach using synchrotron radiationPublication . Silva, Teresa; Figueiredo, M. Ondina; de Oliveira, Daniel Pipa Soares; Veiga, JP; Batista, Maria JoaoThe chemical and physical properties of rhenium render it a highly demanded metal for advanced applications in important industrial fields. This very scarce element occurs mainly in ores of porphyry copper-molybdenum deposits associated with the mineral molybdenite, MoS2, but it has also been found in granite pegmatites and quartz veins as well as in volcanic gases. Molybdenite is a typical polytype mineral which crystal structure is based on the stacking of [S-Mo-S] with molybdenum in prismatic coordination by sulphide anions; however, it is not yet clearly established if rhenium ions replace Mo4+ cations in a disordered way or else, if such replacement gives rise to dispersed nanodomains of a rhenium-rich phase. As a contribution to clarify this question, an X-ray absorption spectroscopy (XANES) study using synchrotron radiation was performed at the Re L3-edge of rhenium-containing molybdenite samples. Obtained results are described and discussed supporting the generally accepted structural perspective that rhenium is mainly carried by molybdenite through the isomorphous replacement of Mo, rather than by the formation of dispersed Re-specific nanophase(s).
- Assessing deep gas fluxes in a volcanic island with no recent volcanism by using noble gases and isotopes - PortugalPublication . Amaral, Helena; Midões, Carla; Kipfer, Rolf
- Benchmarks and sediment source(s) of the 1755 Lisbon tsunami deposit at Boca do Rio EstuaryPublication . Font, Eric; Pires, Cristina Veiga; Pozo, Manuel; Nave, Silvia; Costas, Susana; Ruiz Muñoz, Francisco; Abad, Manuel; Simões, Nuno; Duarte, Sílvia; Rodríguez-Vidal, JoaquínStandardizing the signature of tsunami deposits has been identified as a major limitation for the identification of paleo-tsunami deposits. This limitation mostly arises from the strongly source-dependent nature of these deposits, which in turn determines their composition and depositional architecture, and from the effect of the local morphology of the corresponding depositional environment. Here, we provide new high-resolution mineralogical, geochemical and micro/macrofauna data of the 1755 tsunami layer of Boca do Rio estuary (Algarve, Portugal) with the aim of unraveling the signatures of estuarine tsunami deposits and linking them to possible sediment sources. We also apply for the first time diffuse reflectance spectrophotometry (DRS) analysis. Our results show that the 1755 tsunami deposit of the Boca do Rio estuary is featured by an enhancement in Sr and Ca, which are linked to the input of biogenic and detrital carbonates (shell fragments and limestone clasts) from the beach foreshore and a strong depletion in most terrestrial- and marine-sensitive indicators. The latter is interpreted as resulting from the reworking of the estuarine clays and subsequent dilution within a huge volume of sand eroded from the coastal barrier. It confirms that in the case of the Boca do Rio estuary, the sediment source is essentially proximal and coastal. Textural and mineralogical features between the base and the top of the tsunami layer suggest the imprint of run-up and backwash currents derived from a unique wave. Micro and macrofauna analysis and DRS data of the siliciclastic fraction show slight but significant environmental changes occurring just after the tsunami, which could be provoked by an eventual closure of the estuary mouth.
- Lousal, Portugal : património geológico e mineiro de uma antiga mina na Faixa Piritosa IbéricaPublication . Oliveira, M.; Ferreira, T.; Relvas, Jorge M.R.S.; Pinto, A. M. M.; Pereira, Zélia; Matos, João Xavier; Fernandes, Carlos
- Assessment of potential health risk for inhabitants of S. Francisco de Assis living near Panasqueira mine (Portugal)Publication . Candeias, Carla; Melo, Rita; Ávila, Paula Freire; Ferreira, E.; Salgueiro, Ana Rita; Teixeira, João Paulo
- A new light into old goldPublication . Bidarra, Ana; Figueiredo, M. Ondina; Coroado, João Paulo; Silva, Teresa; Rocha, Fernando