CTM - Artigos em revistas internacionais
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- U-Pb detrital zircon ages in synorogenic deposits of the NW Iberian Massif, Variscan belt : interplay of Devonian-arboniferous sedimentation and thrust tectonicsPublication . Martínez Catalán, José R.; Fernández-Suárez, Javier; Pinto de Meireles, Carlos Augusto; González-Clavijo, Emilio J.; Belousova, Elena; Saeed, AyeshaDetrital zircons from Devonian and Carboniferous synorogenic flysch deposits occurring in an imbricate stack have been dated by laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) to: (1) obtain a maximum depositional age to constrain the maximum age limit for thrusting of exotic terranes in the NW Iberian Massif; (2) correlate the zircon age populations with published ages in nearby units to establish their possible source areas. The maximum depositional ages are Late Devonian for rocks high in the structural nappe pile (Gimonde Formation), in accordance with palynomorph dating, and around the Devonian–Carboniferous boundary for structurally lower samples (San Vitero Formation). Used in conjunction with previously published ages, the new ages are interpreted in terms of the advance of the thrust system responsible for the emplacement of exotic terranes upon the Iberian autochthon during the Variscan collision. Early Variscan zircon population ages indicate the exotic terranes as the source of synorogenic sediments, whereas their scarcity suggests derivation from the Iberian autochthon. One of the samples analysed lacks Variscan detrital zircons; this feature, together with the absence of an Early Palaeozoic zircon age population, puts into question its synorogenic character and suggests that the sample may be representative of the preorogenic parautochthon.
- Assessment of the soil contamination by potentially toxic elements in Aljustrel mining area in order to implement soil reclamation strategiesPublication . Candeias, Carla; Silva, E. Ferreira da; Salgueiro, Ana Rita; Pereira, H. Garcia; Matos, João Xavier; Ávila, Paula Freire
- Geochemistry of granitic aplite-pegmatite sills and petrogenetic links with granites, Guarda-Belmonte area, central PortugalPublication . Neiva, A.M.R.; Ramos, João FarinhaGranitic amblygonite-subtype and lepidolite-subtype, aplite-pegmatite sills intruded a biotite>muscovite granite (G1). Two other biotite>muscovite granites (G2 and G3) and a muscovite>biotite granite (G4) crop out in the area. Variation diagrams for major and trace elements of the Variscan rocks show fractionation trends for a) G1 and G4; b) G2, G3 and aplite-pegmatite sills. The two series are confirmed by the two trends defined by major elements of primary muscovite. The sills also contain Li-bearing muscovite, which has higher Mn, Li, F and paragonite contents and lower AlVI content than primary muscovite from G2, G3 and sills. All sills have pure albite and P2O5 content of K-feldspar and plagioclase increases in the series G2, G3 and sills. Beryl occurs in all sills, but lepidolite and a nearly pure petalite only occur in lepidolite-subtype sills, which are the most evolved sills. Primary topaz and amblygonite have a similar composition in all sills. Aplite-pegmatite sills contain cassiterite, which shows sequences of alternating darker and lighter zones. The former are richer in (Nb + Ta + Fe + Mn) than the latter. Manganocolumbite is common in all sills, but ferrocolumbite only appears in amblygonite-subtype sills and manganotantalite in lepidolite-subtype sills. The sills richest in Li contain reversely-zoned crystals with a homogeneous microlite core and a heterogeneous uranmicrolite rim. Least squares analysis of major elements shows that granite G3 and amblygonite-subtype and lepidolite-subtype aplite-pegmatite sills can be derived from granite G2 magma by fractional crystallization of quartz, plagioclase, K-feldspar, biotite and ilmenite. Modelling of trace elements shows good results for Sr, but magmatic fluids controlled the Rb and Ba contents of the aplite-pegmatite sills and probably also their Li, F, Sn and Ta contents and crystallization of lepidolite, cassiterite and Nb–Ta oxide mineral assemblage. Schorl from the lepidolite-subtype sills that cut granite G1 has higher Mg/(Mg + Fe) than schorl from metasomatised granite at sill walls and resulted from the mixing of magmatic fluids carrying B and some Fe with a meteoric fluid that has interacted with the host granite G1 and carried Fe and Mg. Schorl and dravite, respectively from metasomatised granite and micaschist at sill walls, were also formed from the mixing processes.
- Different methods of sampling and analysis of occupational dust : equipment and techniquesPublication . Barbosa, Fernando; Matos, Maria Luísa Ferreira; Santos, Paula
- Slurry preparation methods affect dental porcelain reliabilityPublication . Pelaez-Vargas, Alejandro; Dussán, Jaime A.; Restrepo, Luís F.; Paucar, Carlos; Ferreira, Jorge Amaral; Monteiro, Fernando J.One-step and incremental mixing procedures are currently used to produce dental ceramic pastes. In the ceramic industry, high quality is obtained using one-step mixing, but in dentistry, the best method has not been yet determined. The purpose of this study is to evaluate the effects of 2 mixing techniques on the biaxial flexural strength and microstructure of dental porcelain. Feldspathic porcelain discs (2 × 15 mm in diameter) were produced and divided according to the ceramic paste preparation method, powder-liquid incremental mixing group (n=50) or one-step mixing, as a control group (n=50). Specimens were tested for biaxial flexural strength and characterized using porosimetry, relative humidity, SEM/EDS, XRD, and FT-IR analyses. Statistical analysis was conducted using Weibull statistics. The Weibull modulus, characteristic strength and relative humidity were compared between groups, using Student's t-test and Mann-Whitney U test (a=.05). The powder-liquid incremental mixing group showed significantly higher values (SD) of Weibull modulus (6.74 (0.70), P<.001) and characteristic strength (79.87 (2.01) MPa, P<.001) when compared to the one-step mixing group (4.94 (0.94) and 75.95 (2.61) MPa). Significantly lower mean (SD) relative humidity values (P=.009) were found for powder-liquid incremental mixing group (20% (0.5%)) compared to one-step mixing group (22% (1%)). XRD spectra showed that the one-step mixing group produced higher amounts of the amorphous phase. Specimens produced by the incremental mixing technique showed higher biaxial flexural strength than one-step mixing.
- The effect of slurry preparation methods on biaxial flexural strength of dental porcelainPublication . Pelaez-Vargas, Alejandro; Dussan, Jaime A.; Restrepo-Tamayo, Luis F.; Paucar, Carlos; Ferreira, Jorge Amaral; Monteiro, Fernando J.
- Dissecting complex magmatic processes : an indepth U-Pb study of the Pavia Pluton, Ossa-Morena Zone, PortugalPublication . Lima, S. M.; Corfu, Fernando; Neiva, A.M.R.; Ramos, João Farinha
- In-situ removal of arsenic from groundwater using permeable reactive barriers with iron based sorbentsPublication . Fiúza, António; Silva, Aurora Futuro; Silva, Maria Aurora Soares; Ferreira, Adelaide; Guimarães, Fernanda
- Geochemistry of granitic aplite-pegmatite veins and sills and their minerals from the Sabugal area, central PortugalPublication . Neiva, A.M.R.; Silva, Paulo Bravo; Ramos, João FarinhaGranitic beryl-columbite-phosphate subtype aplite-pegmatite veins and sills from the Sabugal area intruded a biotite > muscovite granite which is related to another two-mica granite. Variation diagrams of major and trace elements of whole rocks show fractionation trends. REE patterns and δ18O of whole rocks, BaO and P2O5 contents of K-feldspar, anorthite and P2O5 contents of plagioclase, major element and Li contents of muscovite and lithian muscovite support this series. Least squares analysis of major elements indicate that the biotite > muscovite granite and aplite-pegmatite veins and sills are derived from the earlier two-mica granite magma by fractional crystallization of quartz, plagioclase, K-feldspar, biotite and ilmenite. Modelling of trace elements shows that magmatic fl uxes and fl uids controlled the Rb, Sr and Ba contents of aplite-pegmatites, probably also lithium micas (zinnwaldite, polylithionite and rare lepidolite), cassiterite, columbite-tantalite, fl uorapatite and triplite. In aplite-pegmatites, lithian muscovite replaces primary muscovite and late lithium micas replace lithian muscovite. Complexely zoned columbite crystals are chemically characterized and attributed to disequilibrium conditions. Relations of granites and aplite-pegmatites and pegmatites from other Portuguese and Spanish areas are compared. The granitic aplite-pegmatites from Sabugal are moderately fractionated and the granitic complex type aplite-pegmatites from Gonçalo are the richest in Li and Sn, derived from a higher degree of fractional crystallization and fl uxes and fl uids control the Ba and Rb behaviours and Li, Sn, F and Ta concentrations.
- First principles study of copper sulfides (for applications as photoconductors)Publication . Ferreira, Jorge Amaral; Braga, M. Helena