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Item Acesso Aberto Early Ordovician volcanism in Eucísia and Mateus areas, Central Iberian Zone, northern Portugal2012-07-02 - Coke, Carlos; Teixeira, Rui; Gomes, MEP; Corfu, Fernando; Rubio Ordóñez, AThe Eucísia (Alfândega da Fé) and Mateus (Vila Real)areas are located in the Central Iberian Zone, a segment of the northern Gondwana margin which underwent a long Variscan geodynamic evolution. Lithostratigraphically both areas are characterized by a predominance of Precambrian to Cambrian metasedimentary rocks and by the transgressive nature of the Ordovician formations. Continental rifting on the platform of northern Gondwana began around the Middle Cambrian, and opening of the Rheic ocean took place near the Ordovician-Cambrian boundary. In the Eucísia and Mateus areas there is evidence of extensional volcanism related to these events,contemporaneous with a transient inversion, known as the Sardic phase. At Eucísia the Ordovician Armorican Quartzite Formation hosts a < 40 cm thick ash-fall tuff bed, which is mainly composed by muscovite and small amounts of quartz. At Mateus, a subvolcanic porphyritic rock occurs in a 3 m thick vein cutting Precambrian-Cambrian schists. The phenocrysts consist of euhedral/ovoidal plagioclase and microcline and rounded bluish quartz. The groundmass is dark, fine grained and contains quartz, feldspars, muscovite, rare biotite and graphite (identified by XRD). The mineralogical and textural features of this vein resemble those of the augen gneisses from the Ollo de Sapo Formation in Sanabria (Spain), except for a lower degree of deformation/recrystallization. The tuff and the porphyry are both alkali-calcic, peraluminous (ASI ' 1.75 – 2.91) and classified as rhyolites in the R1-R2 diagram. They show moderate REE contents (I ' 78.3 – 182.6), (La/Lu)N values between 11.78 and 12.06, weak negative Eu anomalies (Eu/Eu* ' 0.45 – 0.52) and REE patterns typical of peraluminous granites. Both rocks have a high content of zircon xenocrysts, but also some magmatic zircon prisms which were dated by U-Pb (ID-TIMS) yielding concordia ages that indicate crystallization in the Early Ordovician: the ashfall tuff from Eucísia at 482.1 ± 1.5 Ma and the rhyolite porphyry from Mateus at 478.0 ± 1.7 Ma.Item Acesso Aberto Past, Present and Future of Geochemical Input-Output Budgets1998 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Variação espacial de parâmetros hidroquímicos na bacia hidrográfica do rio Sordo (norte de Portugal).2003 - Alencoão, Ana M.P.; Pacheco, Fernando António Leal; Sousa Oliveira, A.Item Acesso Aberto Geohidrologia das Águas Bicarbonatadas e Gasocarbónicas em Portugal1997 - Sousa Oliveira, A.; Pacheco, Fernando António Leal; Alencoão, Ana M.P.; Portugal Ferreira, M.R.V.Item Acesso Aberto Parâmetros Condicionantes da Descarga Natural em Maciços Fracturados1997 - Alencoão, Ana M.P.; Sousa Oliveira, A.; Pacheco, Fernando António Leal; Portugal Ferreira, M.R.V.Item Acesso Aberto A Heterogeneidade Hidrogeológica num Maciço de Rochas Metamórficas com Fracturas Sistemáticas1997 - Pacheco, Fernando António Leal; Alencoão, Ana M.P.; Sousa Oliveira, A.; Pires, C.P.; Portugal Ferreira, M.R.V.Item Acesso Aberto Weathering and weathering rates on Madeira island2002 - Van der Weijden, C. H.; Pacheco, Fernando António Leal; Loch, J.P.G.Item Acesso Aberto The Delta_18O fingerprint of spring water pathways with evaporating recharge areas2011 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Weathering and hydrochemistry associated with the old mine workings at Fonte Santa (NE of Portugal)2010 - Gomes, M.E.P.; Antunes, I.M.H.R.; Silva, P.B.; Neiva, A.M.R.; Pacheco, Fernando António LealItem Acesso Aberto Plagioclase Weathering Across Hydrological Gradients2010 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Modelling of field weathering rates of plagioclase in Vila Pouca de Aguiar (North of Portugal)2006 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Spring Residence Times: Role in Weathering rates2009 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Weathering rates: a hydrological approach2008 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Topographic and Hydrologic Controls of Spring Water Travel Times and Plagioclase Weathering Rates in Solid Rocks2007 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Aplicação do balanço hídrico em combinação com a relação precipitação escoamento na bacia hidrográfica do rio Corgo2001 - Alencoão, Ana M.P.; Pacheco, Fernando António Leal; Portugal Ferreira, M.R.V.Item Acesso Aberto The Influence of Water Pollution on the Slowed Weathering Rates and Accelerated Biomass Productions Observed in Two Portuguese Granitoid Areas1998 - Van der Weijden, C. H.; Pacheco, Fernando António LealItem Acesso Aberto Exploratory Geochemical Analysis of Groundwater Databases1999 - Pacheco, Fernando António Leal; Van der Weijden, C. H.Item Acesso Aberto Influência litológica no quimismo de águas minerais da “província hidromineral das águas bicarbonatadas sódicas, gasocarbónicas” (norte de portugal): aplicação da análise de correspondências2003 - Sousa Oliveira, A.; Alencoão, Ana M.P.; Pacheco, Fernando António LealItem Acesso Aberto Hydrogeochemistry of Madeira Island1999 - Van der Weijden, C. H.; Pacheco, Fernando António LealItem Acesso Aberto Mineral Weathering Rates and Groundwater Recharge Rates2000 - Pacheco, Fernando António Leal; Van der Weijden, C. H.