Anatexis of metasedimentary rocks in the Iberian Variscan Belt: the example of the Mundão migmatites (Northern Central Portugal)

The oldest rocks exposed in the axial zone of the Iberian massif of Central Northern Portugal (Central Iberian Zone) belong to a thick turbiditic metasedimentary sequence of Neoproterozoic-Lower Cambrian age, consisting of metagreywackes and metapelites with minor calc-silicates and conglomerates. In the Mundão area, this sequence was extensively migmatized during the Variscan orogenic event. Field and structural evidence show that the partial melting conditions were reached in the last stages of crustal thickening (D1), continued during subsequent extensional deformation (D2) and culminated with the emplacement of large volumes of S-type granite magmas in a transcurrent tectonic regime (D3). The Mundão anatectic complex comprises two main migmatite types: metatexites and diatexites, showing in general transitional contacts. The metatexites are composed of dark fine-grained layered hosts and small volumes of quartz-feldspathic veins (leucosomes), whilst the diatexites have igneous looking appearance, larger amounts of the lighter portions and schollen or nebulitic structures. In the latter, the foliation is defined by the presence of biotite rich schlieren and/or the alignment of feldspar crystals in the leucocratic bands. Petrographically, the Mundão migmatite types are distinguished by variations of the modal proportions of the same mineral assemblage (quartz + plagioclase + biotite K- feldspar + apatite + zircon + monazite + opaques). Fibrolitic sillimanite occurs either as small clots of fibres or as needles included within the other mineral phases (plagioclase and muscovite). Tourmaline is a common accessory phase. Large flakes of retrograde muscovite overgrowing the syn-migmatization structures are generally present. The lack of garnet and orthopyroxene in these rocks suggests that melting was dominantly controlled by muscovite breakdown. Whole rock major and trace element geochemistry reveals that the unmigmatized schists and metagreywackes and the darker portions of the metatexites have similar geochemical signatures, characterized by low SiO2 and CaO contents, K2O > Na2O, high Al2O3, Fe2O3T, TiO2, poorly fractionated REE patterns (LaN/YbN = 6.55 – 7.05) and negative Eu anomalies (Eu/Eu* = 0.52-0.56). The similarities encountered appear to indicate that the dark metatexite layers represent partially melted metasediments from which little or no melt extraction occurred. The leucosomes of the metatexites are enriched in SiO2 (74-75%), CaO (0.62-0.77%) and Na2O (2.11-2.79%), depleted in Al2O3, Fe2O3T, TiO2 and REE and have positive Eu anomalies (Eu/Eu* = 1.05-1.58). Their compositions are typical of melts produced either by small amounts of partial melting in disequilibrium conditions and/or by early removal of feldspars from the primary melts (cumulates). In contrast, the leucocratic nebulitic diatexites display SiO2 values varying between 70-72%, K2O enrichment (5.20-6.67%), fractionated REE patterns (LaN/YbN = 11.88 – 22.75) and distinct negative Eu anomalies (Eu/Eu* = 0.34-0.47) and may therefore correspond to more fractionated melts derived from higher melt fractions. The zircon saturation temperatures for samples from the leucosomes of the metatexites and the leucocratic diatexites range between 740 and 780C, suggesting that migmatization occurred mainly via muscovite dehydration reactions. Apparently, the amount of melt generated was enough to flow, implying melt fractions above the melt escape threshold of 20% vol. melt

Processos de fusão parcial no Complexo Migmatítico de Mundão (Centro Norte de Portugal): Evidências geoquímicas

As formações de idade ante-ordovícica estão amplamente representadas na região centro norte de Portugal, onde constituem um espesso conjunto metassedimentar, conhecido na literatura como “Complexo Xisto-Grauváquico ante-Ordovícico” (CXG), ao qual tem sido atribuída uma idade neoproterozóica a câmbrica inferior. Durante a orogenia varisca, as rochas do CXG foram afectadas por deformação polifásica e metamorfismo regional, de intensidade variável. Na área de Mundão, o metamorfismo regional atingiu as condições de fusão parcial, dando origem a um complexo migmatítico (CMM), composto por metatexitos estromáticos, diatexitos “schollen” e diatexitos nebulíticos leucocráticos. Do ponto de vista das relações com a deformação, o processo de migmatização parece ter-se iniciado no final da 1ª fase de deformação (D1), associada ao espessamento crustal do orógeno, prolongando-se durante todo o episódio extensional (D2) e, pelo menos, grande parte da tectónica transcorrente com que se relaciona a 3ª fase de deformação (D3). Os dados de geoquímica de elementos maiores e traço (em particular os padrões de terras raras) mostram que os metapelitos e metagrauvaques não migmatizados e os mesossomas dos metatexitos estromáticos apresentam assinaturas químicas muito semelhantes, caracterizadas por teores baixos de SiO2 e CaO, K2O > Na2O, concentrações altas de Al2O3, Fe2O3, TiO2, padrões de REE pouco fraccionados (LaN/YbN = 6.55 – 7.05) e anomalias negativas de Eu (Eu/Eu* = 0.52-0.56). A semelhança encontrada sugere que os mesossomas não sofreram extracção significativa de “melt”, correspondendo a protólitos relativamente pouco modificados. Em contrapartida, os leucossomas dos metatexitos estromáticos estão enriquecidos em SiO2 (74-75%), CaO (0.62-0.77%) e Na2O (2.11-2.79%), empobrecidos em Al2O3, Fe2O3, TiO2 e REE e mostram anomalias positivas de Eu de amplitude variável (Eu/Eu* = 1.05-1.58). As suas composições são típicas de fundidos gerados por pequenos graus de fusão parcial em condições de desequilíbrio, embora também possam ser atribuídas à precipitação precoce de feldspato a partir dos fundidos primários (cumulados). Por fim, os diatexitos nebulíticos leucocráticos têm conteúdos em SiO2 variando entre 70-72%, exibem um marcado enriquecimento em K2O (5.20-6.67%), padrões de terras raras mais fraccionados (LaN/YbN = 11.88 – 22.75) e pronunciadas anomalias negativas de Eu (Eu/Eu* = 0.34-0.47), pelo que são interpretados como líquidos mais fraccionados resultantes de taxas de fusão superiores. O cálculo das temperaturas de saturação em Zr para as amostras de leucossomas e de diatexitos leucocráticos apontam para temperaturas de fusão entre 740-780C, o que é consistente com processos de anatexia controlados essencialmente por reacções de desidratação de moscovite

New U-Pb zircon ages for Early Ordovician magmatism in Central Portugal

The Mundão anatectic complex is located in the axial zone of the Iberian massif of Central Northern Portugal (Central Iberian Zone). It consists of lenticular bodies of felsic gneisses and stromatic metatexites derived from metasedimentary protoliths of Neoproterozoic-Lower Cambrian age, both showing evidence of incipient to extensive partial melting during the Variscan orogeny. Although the precise age of the migmatization event is still unknown, field and structural evidence show that the partial melting conditions were reached in the last stages of crustal thickening (D1), continued during subsequent extensional deformation (D2) and culminated with the emplacement of large volumes of S-type granite magmas in a transcurrent tectonic regime (D3). The upper limit for crustal melting is provided by the Late Carboniferous age of the S-type granitoids (312.4 2.7 Ma) intruding the Mundão anatectic complex. Due to their transitional contacts with the stromatic metatexites, the felsic gneisses were previously interpreted as diatexites resulting from anatexis of the same pelitic and/or metagreywacke protolith. However, new U–Pb dating by ID-TIMS show that the zircon fractions from one sample of the leucocratic gneisses are concordant and yield a 206Pb/238U weighted average age of 474.5 1.5 Ma. The results obtained reveal that these rocks correspond to orthogneisses instead of sedimentary-derived diatexites and provide a good estimate for the crystallization age of their magmatic protolith. In contrast, the monazite fractions show distinct 207Pb/235U ages of 341.8 2.1 Ma and 453.4 2.0 Ma and may therefore have lost Pb to different extent during Variscan deformation and metamorphism. The preservation of inherited ages of the igneous protolith in the Mundão leucocratic gneisses suggests that zircon was mainly incorporated as restitic material, with only minor precipitation and/or recrystallization during crustal anatexis. The new age of the Mundão orthogneiss brackets the so-called Early Ordovician Sardic unconformity, characteristic of the Central Iberian Zone

The caregiver perspective: an assistive AAL platform

The Ambient Assisted Living area has spawned several projects that aim to help the user on his/her daily activities. The AAL4ALL (ambient assisted living for all) project aims to develop a unified ecosystem using fully compatible devices and services. The UserAccess platform is part of the AAL4ALL and has as a goal to provide assistance to a type of actor that is commonly forgotten in the Ambient Assisted Living area, the caregiver. This paper presents the archi-tecture, implementation, and interfaces, along with a brief analysis of caregiver’s needs and work related issues.Project "AAL4ALL", co-financed by the European Community Fund FEDER, through COMPETE - Programa Operacional Factores de Competitividade (POFC). Foundation for Science and Technology (FCT), Lisbon, Portugal, through Project PEst-C/CTM/LA0025/2013 and the project PEst-OE/EEI/UI0752/2014. Project CAMCoF - Context-aware Multimodal Communication Framework funded by ERDF -European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT - Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project FCOMP-01-0124-FEDER-028980

U-Pb zircon and monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern Portugal

The Viseu area is located in the Central Iberian Zone of the Iberian Variscan Belt and hosts numerous post-thickening, collision-related granitoids intruded into upper and middle crustal levels. The present paper reports high precision U-Pb zircon and monazite ages for four plutons of the Viseu area: The syn-kinematic granitoids of Maceira (314±5 Ma), Casal Vasco (311±1 Ma) and Junqueira (307.8±0.7 Ma) and the late-kinematic biotite monzogranites of Cota (306±9 Ma). This points to a synchronous emplacement of the different syn-kinematic plutons shortly followed by the intrusion of the late-kinematic granites and shows that the Upper Carboniferous plutonism occurred within a short time span of ca. 10 million years. The ascent of granite magmas took place after an extensional tectonic event (D2) and is coeval with dextral and sinistral crustal-scale transcurrent shearing (D3). Field and petrographical evidence suggest a narrow time-span between peak T metamorphic conditions and the intrusion of granitic melts which implies very fast uplift rates accommodated through active tectonic exhumation. Magma compositions evolve through time, reflecting an increasing involvement of mid-crustal sources and the underplating effect of an upwelling asthenospheric mantle at the base of a thinning and stretching continental crust. © 2005 Elsevier B.V. All rights reserved

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Physical activity attenuates the influence of FTO variants on obesity risk: A meta-analysis of 218,166 adults and 19,268 children

Background: The FTO gene harbors the strongest known susceptibility locus for obesity. While many individual studies have suggested that physical activity (PA) may attenuate the effect of FTO on obesity risk, other studies have not been able to confirm this interaction. To confirm or refute unambiguously whether PA attenuates the association of FTO with obesity risk, we meta-analyzed data from 45 studies of adults (n = 218,166) and nine studies of children and adolescents (n = 19,268). Methods and Findings: All studies identified to have data on the FTO rs9939609 variant (or any proxy [r2>0.8]) and PA were invited to participate, regardless of ethnicity or age of the participants. PA was standardized by categorizing it into a dichotomous variable (physically inactive versus active) in each study. Overall, 25% of adults and 13% of children were categorized as inactive. Interaction analyses were performed within each study by including the FTO×PA interaction term in an additive model, adjusting for age and sex. Subsequently, random effects meta-analysis was used to pool the interaction terms. In adults, the minor (A-) allele of rs9939609 increased the odds of obesity by 1.23-fold/allele (95% CI 1.20-1.26), but PA attenuated this effect (pinteraction= 0.001). More specifically, the minor allele of rs9939609 increased the odds of obesity less in the physically active group (odds ratio = 1.22/allele, 95% CI 1.19-1.25) than in the inactive group (odds ratio = 1.30/allele, 95% CI 1.24-1.36). No such interaction was found in children and adolescents. Concl

Hercynian late-post-tectonic granitic rocks from the Fornos de Algodres area (Northern Central Portugal)

The Fornos de Algodres Complex (FAC) comprises several intrusions of late-post-tectonic Hercynian granitic rocks ranging in composition from hornblende granodiorites and quartz monzodiorites, through coarse porphyritic biotite granites and two-mica granites (coarse-, medium- and fine-grained), to muscovite-rich leucogranites. Field and regional constraints show that the emplacement of this large, composite, batholithic complex post-dates the main Variscan regional deformation phases (D1 + D2 + D3) and associated metamorphic events. Field, petrographic and geochemical data suggest a strong genetic relationship between most of the members of the FAC. However, their Rb-Sr and Sm-Nd isotopic signatures appear to rule out any genetic process involving a single homogeneous source and/or closed-system fractional crystallization of the same parental magma. A model involving hybridization of mantle-derived basaltic liquids with crustal anatectic melts followed by further contamination and fractional crystallization is proposed to explain the isotopic and geochemical variation trends defined by the FAC granitic rocks