Tectonics, magmatism, hydrothermalism and sets of flat joints locally filled by Sn---W aplite-pegmatite and quartz veins; southeastern border of the Serra de Estrela granitic massif (Beira Baixa, Portugal)     

C. Derre  M. Lecolle  G. Roger  J. Tavares de Freitas Carvalho 《Ore Geology Reviews》1986,1(1)

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Arsenic in the groundwater of Ouro Preto (Brazil): its temporal behavior as influenced by the hydric regime and hydrogeology     

José Augusto Costa Gonçalves  Jorge Carvalho de Lena  José Fernando Paiva  Hermínio Arias Nalini Jr  Janice Cardoso Pereira 《Environmental Geology》2007,53(4):785-793

In the city of Ouro Preto (MG), water catchment for public supply originates from superficial drainage, springs, old abandoned mines and some driven wells. In the rocks of the region, As is originally found in gold-enriched sulphide-bearing mineral deposits. The weathering process introduces As into the hydrological system by dissolution of this element into the leachate. Measurement of the As content in the groundwater of some catchments was carried out during 1 year and these measurements demonstrated high As content—up to 224 μg L⁻¹ of As(V)—during the rainy season (the maximum concentration limit according to World Health Organization is 10 μg L⁻¹). Lower values were observed during the dry season and in some sampling stations, As was not even detected. The As concentration variability during 1 year shows a strict and direct relationship to seasonal and hydrological conditions. For city authorities, responsible for public water supply, it is necessary to perform a complete inventory of the water sources used and constantly monitor the As content in the water.  相似文献   

Assessment of future trends on groundwater quality in a nitrate vulnerable zone (Esposende–Vila do Conde sector,NW Portugal): towards a combined conceptual and mass transport modelling     

Zeferino  Joel  Carvalho  Maria Ros&#;rio  Lopes  Ana Rita  Jesus  Ros&#;rio  Afonso  Maria Jos&#;  Freitas  Liliana  Carvalho  Jos&#; Martins  Chamin&#;  Helder I. 《Hydrogeology Journal》2021,29(6):2267-2283

Hydrogeology Journal - Nitrate contamination of groundwater is an important public health issue worldwide. For environmental and public health reasons, water should not contain more than...  相似文献   

U-Pb Saturn: New U-Pb/Pb-Pb Data Reduction Software for LA-ICP-MS     

Joao P.A. Silva  Cristiano Lana  Ariela Mazoz  Ian Buick  Ricardo Scholz 《Geostandards and Geoanalytical Research》2023,47(1):49-66

U-Pb Saturn is new freeware for U-Pb LA-ICP-MS data reduction. It has been developed to provide easy interaction with and visualisation of LA-ICP-MS U-Pb datasets, and allows fast and reliable data reduction of hundreds of data-points. Saturn offers dynamic graphic interfaces to quickly view, evaluate, and plot U-Pb and Pb-Pb isotope data. It operates online (or offline), giving the freedom to change parameters and reprocess data at any stage of data acquisition. The main interface allows the user to: (1) choose the best statistics for drift correction, (2) include/exclude offset factors and (3) apply (or not) Pb_c corrections in different modes. Signal intensities are displayed in a separate graphic interface that allows users to interact with the time-resolved signal of individual spot analyses. All graphic windows are interactive; any modification to data treatment (e.g., inclusion or exclusion of analyses of reference material, or modification of the time-resolved signal windows) is instantaneously updated on the data tables. Saturn is particularly attractive for beginners in LA-ICP-MS U-Pb geochronology as it is non-commercial, easy to install, and very interactive. Coding information and a version of the software can be accessed at http://www.air.ufop.br .  相似文献   

Kimberlites distribution in Angola and prospective areas for new discoveries     

Ustinov  Victor N.  Feijo Bartolomeu  Ana M.  Zagainy  Alexander K.  Felix  Joao T.  Mikoev  Igor I.  Stegnitskiy  Yury B.  Lobkova  Ludmila P.  Kukui  Irina M.  Nikolaeva  Evelina V.  Antonov  Sergei A. 《Mineralogy and Petrology》2018,112(2):383-396

Based on a comprehensive analysis of kimberlite pipes of Angola, including the near surface structural setting, deep lithospheric structure, pipe morphology and emplacement, mineralogical and petrographic features, diamond characteristics and locations of secondary deposits four geographical regions have been outlined within Angola representing four types of diamond bearing potential. These areas include high diamond bearing potential pipes, possible potential, no potential, and unclear potential areas. It was found that the depth of magmatism and diamond potential of kimberlites increases from the Atlantic coast in southwestern Angola into the continent in the north-easterly direction. Areas prospective for the discovery of new primary diamond deposits have been identified.

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The role of an extreme flood disturbance on macrophyte assemblages in a Neotropical floodplain     

André Andrian Padial  Priscilla Carvalho  Sidinei Magela Thomaz  Solana Meneghel Boschilia  Roberta Becker Rodrigues  Josilaine Taeco Kobayashi 《Aquatic Sciences - Research Across Boundaries》2009,71(4):389-398

Aquatic macrophytes produce large amounts of organic matter and have an essential structuring role in floodplains. This process highlights the importance of this community to aquatic biodiversity maintenance. We investigated the role of a flood disturbance on the response of macrophyte assemblages in regional and local structuring in the Upper Paraná River floodplain. Plant species were recorded before (November 2006) and after (March 2007) an uncommon increase in water level caused by the El Niño South Oscillation, which is considered a disturbance. Samples were taken in lakes and backwaters located in the floodplain and connected to three distinct rivers (that differentiate three sub-systems). Species richness and the assemblage structure of macrophyte patches underwent significant changes after the flood disturbance, depending on the specific sub-system (rivers) to which the lakes were connected. In addition, flood disturbance had a strong impact on community organization at the local scale. However, regionalization with respect to sub-systems remained significant after the flood disturbance. Our results emphasize the importance of connection to the river on macrophyte community composition and richness, and suggest that flood events in the Upper Paraná River floodplain disrupt community organization only at fine (local) scales.  相似文献   

Interpretation case study of the Sahl El Qaa area, southern Sinai Peninsula, Egypt     

Taha Rabeh  Jorge Miguel Miranda  Joao Carvalho  Andrei Bocin 《Geophysical Prospecting》2009,57(3):447-459

The study area is located in the Sinai Peninsula, which is considered one of the most promising regions for oil resources. Three different tectonic forces affect the area in the triple junction structures associated with the opening of the Gulf of Suez and the strike slip movement along the Gulf of Aqaba. The main goal of this work is to model the structure of the basement rocks in the study area using magnetic methods. To achieve this, a high-resolution land magnetic survey was acquired and the results were combined with existing seismic reflection data. The magnetic interpretation was carried out using the analytical signal, horizontal gradient, Euler and Werner deconvolution and 3D magnetic modelling methods. We concluded that most of the deduced structures are trending in N–S, N35°–N45° west and E–W directions. The Aqaba trend (N15°–N25° east) is barely noticeable. The depth to the basement rocks ranges from 1 km to more than 2 km below sea level and these results are in agreement with the available well log data. In addition, interpretation of seismic reflection sections was carried out and compared with overlapping magnetic profiles interpreted using Euler deconvolution. They show that the sedimentary section was affected by the basement tectonics, with faults extending from the basement upwards through the sedimentary cover. These faults constitute good potential structural traps for oil accumulation.  相似文献   

A note on a mineralogical analysis of the sediments associated with the Plata River and Patos Lagoon outflows     

Edmo J.D. Campos  Swapna Mulkherjee  Alberto R. Piola  Flavio M.S. de Carvalho 《Continental Shelf Research》2008

Riverine waters bring to seas a variety of suspended materials, which are ultimately deposited on the shelf or exported to the deep ocean. Investigation of the mineralogical contents of these continental-borne constituents on seafloors may reveal valuable information about the environmental conditions in the drainage basin. In this note we report results of X-ray diffraction and other analysis of sediments in bottom samples collected on the continental shelf under influence of the Plata River and the Patos Lagoon, in South America. The analysis reveals that non-clay materials are mostly concentrated south of 33°S, while clay sediments are relatively more abundant further north. We propose that such distributions are controlled by the circulation pattern and water mass distribution of the lower and upper layers, respectively.  相似文献   

The growth of linear perturbations in generic defect models for structure formation     

P. P. Avelino  J. P. M. de Carvalho 《Monthly notices of the Royal Astronomical Society》1999,310(4):1170-1174

We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters h ,     and     . We show that for wavenumbers k ≳0.01  h  Mpc⁻¹ the spectrum of density and velocity perturbations scales in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more-or-less incoherent nature of the source, the small-scale power spectrum of the source and of deviations from scaling that naturally occur at late times if     .  相似文献   

Seasonal variation of particulate heavy metals in the Lower Paraíba do Sul River, R.J., Brazil     

C. E. V. Carvalho  A. R. C. Ovalle  C. E. Rezende  M. M. Molisani  M. S. M. B. Salomão  L. D. Lacerda 《Environmental Geology》1999,37(4):297-302

 Temporal and spatial variability of particulate metal concentrations (Cu, Cr, Zn, Mn and Fe) were investigated in the lower drainage basin of the Paraíba do Sul River. The results showed that the spatial variability was not important for all the studied metals, however, temporal variations seems to be considerable. In general, two distinct behaviors were observed for particulate heavy metals: (1) metal concentration increase together with water flow (Fe and Cu) and (2) concentration decrease with increasing water flux (Zn, Cr and Mn). The Fe and Cu behavior is probably due to the strong association of these metals with surface runoff, although their sources seem to be distinct. Iron probably originates from the regional soils rich in iron oxides, and Cu is possibly associated to the large-scale use of copper fungicides in the sugar cane plantations. The opposite trend observed for Zn, Cr and Mn probably reflects the importance of the industrial and urban effluents as a secondary source of these elements for the system. Their behavior is probably associated with the dilution effect caused by the input of a suspended matter poor in these metals originated from the surface runoff during the rainy season. Received: 4 March 1998 · Accepted: 30 June 1998  相似文献