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Carvalho, Maria do Rosário
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Preferred name
Carvalho, Maria do Rosário
Official Name
M.R. Carvalho
Alternative Name
Rosário Carvalho
ORCID
Scopus Author ID
7201413947
6 results
Now showing 1 - 6 of 6
- PublicationRestrictedPreliminary Geochemical and Isotopic Results in Thermal and Cold Waters of Graciosa Volcanic Island (Azores)(2017)
; ; ; ; ; ; ; ; ; ; ; Graciosa Island is located in the Azores Archipelago, along the so-called Terceira Rift, NE boundary of the Azores Plateau. From the hydrochemical point of view, two types of Na-Cl groundwater systems were identified: a cold aquifer system emerging at springs and exploited through boreholes for public water supply with different degrees of mineralization, and a hydrothermal system with issuing temperatures around 45 ºC. Geothermometers applied to the thermal waters point to deep temperature around 167 ºC and to immature waters, not reaching complete equilibrium with the reservoir rock. The isotopic composition and geochemistry of the thermal waters indicate mixture groundwater - seawater in different percentages and ion-exchange mechanisms that will be able to: i) increase groundwater salinity, ii) strongly change the isotopic composition to more enriched values, with different degrees of mixing.257 9 - PublicationOpen AccessNitrogen isotope measurements on hydrothermal fluids from Azores (S. Miguel, Terceira and Graciosa) Islands, Portugal(2009-08-30)
; ; ; ; ; ; ;Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Carreira, P.M.; Instituto Tecnológico e Nuclear, Estrada Nacional nº 10, 2686-953 Sacavém, Portugal ;Carvalho, M.R.; Fac.e Ciências de Lisboa, Departamento de Geologia, CeGUL, 1749-016 Lisboa, Portugal ;Marques, J.M.; Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal ;Nunes, J.C.; Department of Geosciences, University of the Azores, Portugal; ; ; ; ; ; ;Savard, Martine M.; Geological Survey of Canada, QuebecWe present the first nitrogen isotope data from hydrothermal fluids of Graciosa, Terceira and S. Miguel Islands (Azores, Portugal), together with helium isotope composition. 15N values are slightly enriched in light isotopes (from -0.7‰ to -2.2‰) with respect to air, while 3He/4He ratios range from 5 to 6 Ra in Sao Miguel island and from 8 to 9.1 Ra in Graciosa and Terceira islands. The latter values are similar to those found in olivine phenocrysts of basalts (Moreira et al., 1999; Madureira et al., 2005). Such isotope signatures seem to point to the presence of two different deeply-derived end-members: a 3He-rich primitive end-member evident in Terceira and Graciosa islands samples and a 3He-poor end-member characterizing samples from S. Miguel island. According to Madureira et al. (2005), the He primitive component which is more evident in the central parts of the Azores archipelago has to be related to a lower mantle contribution into the prevailing MORB component. On the contrary, the origin of the radiogenic crustal component is still open and debated between the contribution of recycled terrigenous sediments (Turner et al., 1997) and oceanic mantle lithosphere (Schaefer et al., 2002). Since 15N values from fluids vents and inclusions in basalt glasses were discovered to be good geochemical tracers of magma genetic processes, we determined molecular and isotope nitrogen composition (15NN2) in some hydrothermal fluids with the aim to provide additional information on the mantle composition beneath the Azores archipelago. Based on the N2/36Ar ratio we computed for each samples the 15N values of the non-atmospheric nitrogen (15Ndeep). Volatiles emitted from Graciosa and Terceira islands seem to have a common deep nitrogen isotope signature of about -1.5‰ likely resulting from a mixing between lower mantle (15N from 1‰ to 4‰) and upper mantle (15NMORB from -3‰ to -7‰). On the other hand, the 15Ndeep feeding the fumaroles at S. Miguel is close to -5.5‰. Such a 15N-depleted values seem to indicate a probable nitrogen origin from a deep source derived from the recycling of ancient oceanic plate into the upper mantle (MORB). rather than from the recycling of terrigenous sediments transported on top of the descending plate that should have lead to 15N-enrichments.165 94 - PublicationRestrictedNitrogen isotopes determination in natural gas: analytical method and first results on magmatic, hydrothermal and soil gas samples(2010-06)
; ; ; ; ; ; ; ; ;Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Oliveri, Y.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Sollami, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Carreira, P.; Instituto Tecnológico e Nuclear, Sacavém, Portugal ;Carvalho, M. R.; Faculdade de Ciências de Lisboa, Departamento de Geologia, CeGUL, Lisboa, Portugal ;Marques, J. M.; Instituto Superior Técnico, Lisboa, Portugal ;Nunes, J. C.; Department of Geosciences, University of the Azores, Sao Miguel, Azores, Portugal; ; ; ; ; ; ; A continuous-flow GC/IRMS technique has been developed to analyse δ15N values for molecular nitrogen in gas samples. This method provides reliable results with accuracy better than 0.15‰and reproducibility (1σ) within ±0.1‰ for volumes of N2 between 1.35 (about 56 nmol) and 48.9μL (about 2μmol). The method was tested on magmatic and hydrothermal gases as well as on natural gas samples collected from various sites. Since the analysis of nitrogen isotope composition may be prone to atmospheric contamination mainly in samples with low N2 concentration, we set the instrument to determine also N2 and 36Ar contents in a single run. In fact, based on the simultaneously determined N2/36Ar ratios and assuming that 36Ar content in crustal and mantle-derived fluids is negligible with respect to 36Ar concentration in the atmosphere, for each sample, the degree of atmospheric contamination can be accurately evaluated. Therefore, the measured δ15N values can be properly corrected for air contamination.376 48 - PublicationOpen AccessGeochemistry of groundwater from Graciosa Island (Azores): A contribution to the hydrothermal system conceptual model(2011-08-14)
; ; ; ; ; ; ;Carvalho, M.R.; 1Universidade de Lisboa, Faculdade de Ciencias, Depart. Geologia/CeGUL, Portugal ;Carreira, P.; Instituto Tecnologico e Nuclear, Lisboa, Portugal ;Marques, J.M.; Instituto Superior Tecnico, Lisboa, Portugal ;Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Nunes, J.C.; Universidade dos Açores & INOVA Inst., Azores, Portugal; ; ; ; ; Graciosa island is located in the Azores Archipelago, along the so-called Terceira Rift, a major tectonic structure that makes the NE boundary of the Azores Plateau. In general terms, it includes a basaltic plataform on the NW and a silicic poligenetic volcano with caldera on the SE, the Graciosa Caldera Volcano. This volcano has produced significant tephra falls, pyroclastic flows, lahars, and lava flows, both of basaltic s.l. and trachitic s.l. composition. The hydrothermal system shows fumarolic emissions inside the volcano caldera and thermal springs located along the shoreline. This system is exploitated in a thermal building through shallow and deep (110 m) boreholes, near the coast. In Graciosa two types of Na-Cl groundwater systems can be identified: 1) a cold one emerging at springs and exploited by wells for public water supply, and 2) a hydrothermal system with temperatures around 40-44 °C. The cold groundwaters have pH higher than 7 and different degree of mineralization, according to the proximity to the sea. The thermal waters show mixing with seawater, pH varying between 6.20 and 6.94, 166 mg/L of SiO2, and significant concentration of metals, such as Mn, Fe, Co, Ni, Cu and Zn. The thermal water mineralization varies strongly, showing EC from 8.87 mS/cm (shallow water) to 47.4 mS/cm (deeper water). The higher mineralized water is rich in CO2(g), with 2130 mg/L of total dissolved CO2. Geothermometers application reveals aquifer temperature around 167 °C and immature/mixed waters, not reaching complete equilibrium with reservoir rock. The geochemistry of the thermal waters indicates the occurrence of seawater/host rock interaction processes at high temperature and slightly acid conditions, favored by CO2(g) input, and a different degrees of mixing with cold and shallow groundwaters.357 133 - PublicationRestrictedMantle-derived carbon in Hercynian granites. Stable isotopes signatures and C/He associations in the thermomineral waters, N-Portugal(2010)
; ; ; ; ; ;Carreira, P. M.; Instituto Tecnológico e Nuclear, Estrada Nacional n° 10, 2686-953 Sacavém, Portugal ;Marques, J. M.; Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal ;Carvalho, M. R.; Universidade de Lisboa, Faculdade Ciências, Departamento Geologia, CeGUL, Ed.C6, Campo Grande, 1749-016 Lisboa, Portugal ;Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; ; ; ; Na–HCO3–CO2-rich thermomineral waters issue in the N of Portugal, within the Galicia-Trás-os-Montes region, linked to a major NNE-trending fault, the so-called Penacova-Régua-Verin megalineament. Along this tectonic structure different occurrences of CO2-rich thermomineral waters are found: Chaves hot waters (67 °C) and also several cold (16.1 °C) CO2-rich waters. The δ2H and δ18O values of the thermomineral waters are similar to those of the local meteoric waters. The chemical composition of both hot and cold mineral waters suggests that water–rock reactions are mainly controlled by the amount of dissolved CO2 (g) rather than by the water temperature. Stable carbon isotope data indicate an external CO2 inorganic origin for the gas. δ13CCO2 values ranging between −7.2‰ and −5.1‰ are consistent with a two-component mixture between crustal and mantle-derived CO2. Such an assumption is supported by the 3He/4He ratios measured in the gas phase, are between 0.89 and 2.68 times the atmospheric ratio (Ra). These ratios which are higher than that those expected for a pure crustal origin (≈0.02 Ra), indicating that 10 to 30% of the He has originated from the upper mantle. Release of deep-seated fluids having a mantle-derived component in a region without recent volcanic activity indicates that extensive neo-tectonic structures originating during the Alpine Orogeny are still active (i.e., the Chaves Depression).467 15 - PublicationOpen AccessHelium isotopes distribution in NW Iberian peninsula: evidences of a local neotectonic activity(2011-08-04)
; ; ; ; ; ; ;Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Carreira, P.; Instituto Tecnológico e Nuclear, Sacavém, Portugal ;Carvalho, M.R.; Universidade de Lisboa, Faculdade CienciasDpt. Geologia, Lisboa ;Marques, J.M.; Instituto Superior Técnico, Lisboa ;Antunes da Silva, M.; UNICER Bebidas, S.A. S. Mamede de Infesta; ; ; ; ; ; ; ;Demény, Attila; Instute for geochemical research, Hungarian Academy of SciencesIn this work we report new data on He abundances and isotope ratios (3He/4He) from gas associated to some thermal and CO2-rich mineral waters in N-Portugal. Collected gas samples are mainly CO2-dominant except two sites where gas is N2-rich. All the sampling sites are characterized by exceptionally high helium contents with 3He/4He ratios, corrected for air contamination, varying considerably from 0.09 to 2.68 Ra. In all sites, the 3He/4He ratios are higher than that typical for stable continental areas thus indicating a variable but not-negligible (up to 30%) contribution of mantle-derived primordial He. In all the CO2-rich waters, CO2/3He ratios and 13CCO2 are comparable with mantle values, thus suggesting a magmatic origin also for CO2. On the contrary, in the N2-rich waters He is mainly radiogenic, and CO2 is organic in origin. Since no recent volcanic activity is observed in NW Iberia, high 3He/4He values could be due, at least, to three processes: a) releasing of gas from the local upper mantle through deep extensional fault systems; b) releasing of magmatic volatiles from crustal reservoir(s) formed during past volcanic activity; c) degassing of a subsurface emplaced magma body. Mantle He flux in N-Portugal has been estimated to be up to 3 orders of magnitude higher than that typical for stable continental areas, thus suggesting, in this area, the presence of a tensional tectonic regime. This implies that mantle gases could migrate upward probably through inherited tectonic structures reactivated by neotectonic activity. The third possible scenario seems to be less plausible since seismic surveys carried out in NW Iberian did not find any significant evidence of mantle intrusion in the crust. The observed spatial variability in mantle-derived contribution could reflect the geometry of the granitic plutons in this area, thus supporting the hypotheses of an upper mantle degassing. Alternatively, it could be the result of a lateral migration of magmatic volatiles stored in a crustal reservoir.318 170