Helena C.B. Martins

Helena C.B. Martins
University of Porto | UP · Faculty of Sciences

PhD

About

73
Publications
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287
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Introduction
Helena C.B. Martins currently works at the Faculty of Sciences, University of Porto. Helena does research in Geochemistry, Geology , Mineralogy and Geochronology of variscan granites and migmatitic rocks. Their most recent publication is 'Variscan Magmatism'.
Additional affiliations
September 2001 - present
University of Porto
Position
  • Professor (Assistant)

Publications

Publications (73)
Article
Full-text available
The Valpaços (ValG) and Freixo de Numão (FNG) ilmenite-type granites, were studied to understanding ascent and emplacement mechanisms and deformation patterns evolution during the end of Variscan orogeny in Northeastern Portugal. Anisotropy of magnetic susceptibility, microstructural and microfracturing studies were performed in both granites. The...
Conference Paper
Full-text available
A granite porphyry dyke, E-W trending in general and about 21 km long, plus several small microgabbro outcrops can be found in the Vila Nova de Foz Côa (VNFC) region of northern Portugal. While the porphyry is mostly composed of quartz, K-feldspar, muscovite, albite-oligoclase (An6-18), cordierite, and biotite, the microgabbros are rich in labrador...
Conference Paper
Full-text available
The Permo-Carboniferous hypabyssal magmatism is a well-recorded igneous event throughout southwestern Europe, associated with the post-collisional setting that followed the Variscan orogeny. In northern Portugal, this episode is represented by porphyry, lamprophyre, and dolerite dykes. In the present work, the magnetic mineralogy and fabrics of sel...
Article
Full-text available
During the final stages of the Variscan orogeny, several subvolcanic dykes intruded throughout NW and SW Europe. In northern Portugal, the microgranite and lamprophyre of the Lamas de Olo region constitute a local manifestation of this magmatic event. To understand their petrogenesis, field, petrographic, and bulk-rock geochemical studies were unde...
Article
Full-text available
Three of the largest granite porphyries of northern Portugal were studied to improve current knowledge on the regional felsic vein hypabyssal magmatism. All porphyries exhibit microcrys-talline groundmasses of variable granularity (composed of quartz, K-feldspar, and muscovite), quartz, K-feldspar, plagioclase, biotite, and cordierite phenocrysts,...
Conference Paper
Full-text available
The onset of the final stages of the Variscan orogeny in the Central Iberian Zone (CIZ) is marked by the emplacement of several late to post-tectonic granite melts. The following transition into an extensional regime is associated with subvolcanic magmatism, commonly represented by veins and masses of rhyolitic porphyries, dolerites, and lamprophyr...
Conference Paper
Full-text available
The existence of granitic or rhyolitic porphyries and other subvolcanic lithologies in the Central Iberian Zone has been recognized since the 20th century. However, the geological studies concerning these rocks have been mainly focused on the mafic specimens (lamprophyres and dolerites). In this research, three of the largest granite porphyries of...
Conference Paper
Full-text available
Whole-rock geochemical data of the Lamas de Olo microgranite and lamprophyre veins are presented for the first time. The results suggest that the felsic vein derived from a highly-evolved, plagioclase-rich, crustal source that was uncontaminated by mantle or young crustal influences, while the magmatic source of the lamprophyre was probably located...
Conference Paper
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At the east sector of the Lamas de Olo granitic pluton, two veins, one microgranitic and the other lamprophyric, are emplaced into different facies of the Vila Real granite. The microgranite is characterized by a quartz + potassium feldspar ± muscovite ± apatite ± biotite ± brookite/anatase mineral assemblage, while the lamprophyre has plagioclase,...
Conference Paper
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In Vila Pouca de Aguiar there are two porphyries of granitic/rhyolitic composition that intrude the biotite-rich, post-tectonic, VPA granite. Both are N-S trending, being designated Loivos and Póvoa de Agrações porphyries. The VPA porphyries exhibit porphyritic texture and microcrystalline groundmass. Their characteristic mineral assemblage is comp...
Chapter
Full-text available
This chapter aims to identify, characterize and locate the main facts/events related to orogenesis in the Iberian Peninsula. Its succession in space and time determines the geodynamic environment of the broader geological phenomenon corresponding to the Variscan cycle. In this sense, this section comprises two parts: I—The Iberian orogenic magmatis...
Conference Paper
Full-text available
The mechanisms involved in alkali-aggregate reaction and the characteristics of reactivity of some aggregates are not completely understood, although tens of thousands of mortar and concrete prisms have been tested in the laboratory and field exposure sites have been installed in a number of countries. Aggregates are the least well understood compo...
Preprint
Full-text available
Resumo: A região de Guimarães possui uma grande diversidade de litologias plutónicas hercínicas, destacando-se granitóides biotíticos e vaugneritos. Enquanto os granitóides são peraluminosos, tendo tido origem em melts gerados a nível basicrustal, resultantes da fusão parcial de rochas metaígneas/metagrauváquicas com alguma contribuição mantélica (...
Conference Paper
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The Vila Nova de Foz Côa granitic porphyry vein, which extends east into the Freixo de Espada à Cinta region, is one of the largest vein structures occurring in the Central Iberian Zone. This vein presents an extension of about 21 km, in an E-W direction. It intrudes hercynian granites and prior-paleozoic metassediments. Petrographically it present...
Conference Paper
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Nos arredores do Porto, no setor NW da faixa magmato-metamórfica Porto-Viseu estão caraterizadas rochas gnaisso-migmatíticas, nomeadamente no Complexo Migmatítico do Mindelo (CMM) e nos Migmatitos de Lavadores-Madalena (MLM), englobados em diferentes unidades geotectónicas do Maciço Ibérico. Estes complexos apresentam bastante similaridade litológi...
Conference Paper
Full-text available
The granitic rocks of the Guimarães region are synorogenic with an emplacement age between 319 and 290 My. It is possible to distinguish different emplacement periods in relation to the D3 phase of the Variscan orogeny: syn-tectonic granitoids (Felgueiras granodiorite and Lousada granite), late-tectonic (Ronfe granodiorites and Guimarães granites)...
Conference Paper
Full-text available
The granitic rocks of the Guimarães region are synorogenic with an emplacement age between 319 and 290 My. It is possible to distinguish different emplacement periods in relation to the D3 phase of the Variscan orogeny: syn-tectonic granitoids (Felgueiras granodiorite and Lousada granite), late-tectonic (Ronfe granodiorites and Guimarães granites)...
Conference Paper
Full-text available
Calc-silicate and amphibolitic nodules occur in the gneiss-migmatitic outcrops in the coastal zone of Vila Nova de Gaia, Madalena. The calc-silicate nodules present a zonal structure and are texturally uniform, whereas the amphibolitic nodules have more diverse textures. The amphibolitic nodules are very similar, in the lithological and petrographi...
Code
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In the NW sector of the Porto-Viseu Metamorphic Belt migmatites associated with granites are intrusive in metasedimentary rocks of the Schist-Greywacke Complex. West of Porto Granite outcrops the Fânzeres Granite, a granitoid of peculiar sigmoidal geometry, cartographed as an alkaline gneissic granite rich in garnet, limited at west and east by two...
Conference Paper
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Resumo: O complexo migmatítico do Pedregal e o Complexo Anatéctico de Figueira de Castelo Rodrigo-Lumbrales (CAFCR-L) são áreas onde afloram rochas migmatíticas associadas a granitos de tipo-S, sin-orogénicos, estando estes separados de rochas de baixo grau metamórfico do Supergrupo Dúrico-Beirão por zonas de cisalhamento. Embora este seja um impor...
Conference Paper
Full-text available
Resumo Foram analisadas, para isótopos de Sr e Nd, cinco amostras de metassedimentos pertencentes ao Complexo Xisto-Grauváquico (CXG), ou Supergrupo Dúrico-Beirão, de idade ante-ordovícica, mais precisamente ediacarana. Quatro das amostras são de litologias pertencentes ao Grupo das Beiras do CXG, tendo sido colhidas na área de Sarnadas do Ródão, r...
Conference Paper
Full-text available
The NW sector of Porto-Viseu metamorphic belt, in the western border of Central Iberian Zone (CIZ), is characterised by the confluence of two major variscan shear zones: the Douro-Beira shear zone (DBSZ) and the Porto-Tomar shear zone (PTSZ). This later structure is a major geotectonic alignment from which different models of tectonic evolution hav...
Conference Paper
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Resumo Neste trabalho são apresentados os resultados isotópicos Sr-Nd do Granito do Pedregal e das rochas gnaisso-migmatíticas associadas, aflorantes na Zona Centro-Ibérica noroeste de Portugal, no bordo oriental do maciço granítico sin-orogénico do Porto. O granito do Pedregal é um pequeno corpo alongado na direcção NW-SE, intrusivo em micaxistos...
Conference Paper
Full-text available
Alkali-silica reaction is a mechanism of deterioration of concrete structures which is associated with the composition of the rocks used as aggregates. The assessment of aggregates to evaluate their potential reactivity to alkalis is made both by visual methods and laboratory expansion tests. There are a number of national standards regarding the p...
Article
Full-text available
The synorogenic Variscan granite-migmatite complex in study outcrops in the Central Iberian Zone, northern Portugal. The Pedregal granite dated of 311±5 Ma has an NW-SE elongated shape and is intrusive in staurolite-micaschist and banded gneiss-migmatite rocks, with local igneous breccias along the contact. This granite is a fine to medium-grained...
Article
Full-text available
The Pedregal granite outcrops in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex sub-concordant with the regional metamorphic structures. It is a granitoid (ca. 3 km2) with an elongated NW-SE shape intruded in staurolite-micaschist and banded gneiss-migmatite rocks, with local i...
Article
Full-text available
O maciço granito pós-tectónico de Lavadores-Madalena, ocorre num sector chave da evolução geodinâmica varisca da Zona de Cisalhamento Porto-Tomar. Dados cartográficos, estruturais e de fabric magnético indicam que os granitos do maciço exibem uma fluência magmática condicionada pela convergência de estruturas de orientação NNW-SSE a N-S com estrutu...
Article
Full-text available
In northern Portugal, large volumes of granitoids were emplaced during the last stage (D3) of the Variscan orogeny and display a wide range of petrological signatures. We studied the morphologies and internal structures of zircons from syn-, late- and post-D3 granitoids. The sin-D3 granitoids include the Ucanha–Vilar, Lamego, Felgueiras, Sameiro, a...
Conference Paper
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The gneiss-migmatitic rocks that crop out in the Madalena coast, in Vila Nova de Gaia, are part of a metamorphic belt, adjacent to the sin-tectonic massif of Porto in its western edge, and which was later intruded by the post-tectonic granite of Lavadores. A lithological and petrographic study of the metatexite and diatexite rocks was performed. Th...
Article
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The Santa Eulália Plutonic Complex (SEPC) is a late-Variscan granitic body located in the northern part of the Ossa Morena Zone, a inner zone of the Variscan Iberian Massif. The SEPC host rocks are composed of meta-igneous and metasedimentary units, from Upper Proterozoic to Paleozoic ages, with a NW-SE structure, cross cutted by the SEPC. The SEPC...
Article
Full-text available
A group of slightly peraluminous Variscan plutons in Northern Portugal were selected from the study of zircon composition. The selected plutons are: the Vila Pouca de Aguiar and the Lavadores-Madalena plutons with I-type affinities and the Vieira do Minho pluton, an l-S transitional type. Zircon occurs as euhedral to subhedral crystals and exhibit...
Article
Full-text available
The Santa Eulália Plutonic Complex (SEPC), located in the Ossa Morena Zone (south Portugal), is composed of a medium- to coarse-grained pink granite (G0-type) and a central grey medium-grained biotite granite (G1-type). Available Rb-Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabri...
Article
Full-text available
The petrogenetic characterization of anatectic granites in Variscan Orogen and their spatial association with gneissic-migmatite thermal domes has been advocated and demonstrated in a more integrated way combining geological, geochemical, isotopic and geochronological data. Migmatitic rocks associated with the “Granito do Porto” are referred since...
Article
Full-text available
The Pedregal granite is exposed in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex which includes the Porto granite, subconcordant with the regional structures. It is a small body with an elongated NW-SE shape, intruded in staurolite-micaschist and banded gneiss-migmatite rocks,...
Article
Full-text available
O extremo NW da cintura metamórfica Porto-Viseu é caracterizado por magmatismo sin-tectónico e pós-tectónico, associado a rochas migmatíticas e a uma zonalidade metamórfica condensada variando progressivamente da zona da clorite até à zona da silimanite. A presença de estaurolite e a ausência de cordierite nas paragéneses metamórficas exclui condiç...
Article
Full-text available
Resolving time differences between successive magmatic pulses in granitoid plutons is often a difficult task. High-precision ages, obtained by U-Pb SHRIMP in Lavadores granite, provide evidence that the crystallization of this granite happened at 294±3 Ma which is more precise that a previous age obtained by conventional U–Pb method on multigrain z...
Article
Full-text available
Resumo: O extremo NW da cintura metamórfica Porto-Viseu é caracterizado por magmatismo sin-tectónico e pós-tectónico, associado a rochas migmatíticas e a uma zonalidade metamórfica condensada variando progressivamente da zona da clorite até à zona da silimanite. A presença de estaurolite e a ausência de cordierite nas paragéneses metamórficas exclu...
Article
Full-text available
Modern day Portland-cement concrete was for decades considered to be a long lasting material, until in the 1940s it was recognised that concrete could deteriorate as the result of chemical reactions between Portland cement and some components of the aggregates. Research has been undertaken since then in order to find the best test methods for ident...
Article
Full-text available
The Pedregal granite is exposed in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex which includes the Porto granite, subconcordant with the regional structures. It is a small body with an elongated NW-SE shape, intruded in staurolite-micaschist and banded gneiss-migmatite rocks,...
Article
Full-text available
The NW of the Porto-Viseu metamorphic belt is characterized by syn-tectonic and post-tectonic magmatism, associated with migmatites. The surrounding metasedimentary rocks show narrow and progressive metamorphic zoning ranging from chlorite to sillimanite zone. The metamorphic paragenesis with staurolite and without cordierite exclude barometric con...
Conference Paper
Full-text available
The Pedregal granite is exposed in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex sub-concordant with the regional structures. It is a small body (ca 3km 2) with an elongated NW-SE shape, that intruded in staurolite-micaschist and banded gneiss-migmatite rocks, with local igneo...
Conference Paper
Full-text available
The Pedregal granitoid, exposed of an area with of ca 3 km 2 , is located in the Central Iberian Zone, northern Portugal and belongs to a synorogenic variscan granite-migmatite complex sub-concordant with the regional structures. It has an elongated shape with NW-SE trending sub-concordant with country rocks, and is a fine-grained biotite-rich gran...
Article
Full-text available
In the Central Iberian Zone synorogenic (syn- and late-D-3, the last deformation phase) composite batholiths of biotite-rich granitods with peraluminous character are well represented. We report here U-Pb zircon and monazite ages, geochemical, Sr-Nd-O isotopic data and Anisotropy of Magnetic Susceptibility (AMS) studies for the late-D-3 Vieira do M...
Article
Full-text available
Abstract: The central-northern region of Portugal mainland comprises an important W-Sn metallogenic province composed of various W, W-Sn, W-Mo and Sn hydrothermal lode deposits spatially related to Variscan granites. These granites are usually categorised into two main groups: the two-mica granites and biotite-bearing granites. As the granite serie...
Article
Full-text available
The central-northern region of Portugal mainland comprises an important W-Sn metallogenic province composed of various W, W-Sn, W-Mo and Sn hydrothermal lode deposits spatially related to Variscan granites. These granites are usually categorised into two main groups: the two-mica granites and biotite-bearing granites. As the granite series reflect...
Article
Full-text available
In the Iberian Massif large volumes of granitic rocks were emplaced during the Variscan orogeny, mainly during the last ductile deformation phase D3. After that, an extensional tectonic regime controls the emplacement of several Fe-K subalkaline post-D3 plutons. Geochemical and isotopic results of post-D3 biotite granites in northern Portugal (Pene...
Article
Studies of Anisotropy of Magnetic Susceptibility (AMS) and U-Pb geochronology, in zircon fractions, were carried out in a magnetite type-granite, the Lavadores granite, which is an example of a late to post-orogenic Variscan granite in northern Portugal (NW Iberian Peninsula). The U-Pb zircon analyses yield an age of 298±11 Ma that is considered to...
Article
Multidisciplinary studies integrating, U–Pb geochronology, whole-rock geochemical data, isotope geochemistry, anisotropy of magnetic susceptibility (AMS) studies and gravimetry were carried out on the Vila Pouca de Aguiar and the Águas Frias-Chaves porphyritic biotite granite plutons. Both plutons occur independently in a distance of about 20 km. T...