Regional Structural Analysis by Remote Sensing for Mineral Exploration,Paraiba State,Northeast Brazil     

Chan Chiang Liu  Manoel de Araújo Sousa Jr.  Tumkur Rajarao Gopinath 《国际地球制图》2013,28(1):70-77

Abstract

Photogeological techniques were used to analyze Landsat‐TM images of the Paraiba State, which resulted in the identification of the following structures: lineaments of regional extent, short en echelon lineaments, intricate ramification of the wrench system, and infrastructures among major lineaments and circular or ring structures. This lineament map was correlated to existing geological maps, to areas of known hydrothermal mineralization (Cu, Au, Mo, Ni, W and Ti), and the lineament map was verified in the field reconnaissance. Due to lack of systematic studies of the geology and natural resources of the region the mineral exploration is still in rudimentary stages. The objective of this research is to emphasize the detection and analysis of lineaments, their patterns, and geometry and their relations with the occurrence of mineral resources and its exploration in areas as yet explored. A large number of mineral‐bearing pegmatites of the region are controlled by major lineaments and associated minor lineaments. It is believed that the structures of interest in search for mineral deposits are warping part of the minor shear zones, the intersections of short and regional lineaments, and the circular features.  相似文献   

Integrative assessment of organotin contamination in a southern European estuarine system (Ria de Aveiro, NW Portugal): tracking temporal trends in order to evaluate the effectiveness of the EU ban   总被引：1，自引：0，他引：1  

Sousa A  Matsudaira C  Takahashi S  Tanabe S  Barroso C 《Marine pollution bulletin》2007,54(10):1645-1653

Organotin (OT) compounds have been used as biocide agents in antifouling paints since the mid 1960s and are now ubiquitous in the marine environment. Due to their high toxicity to non-target species they were banned from antifouling paints in the European Union in 2003 (2002/62/EC directive). The aim of the present work is to assess any obvious decline of the OT environmental levels at Ria de Aveiro (NW Portugal) after the ban. The organotins - monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPT), diphenyltin (DPT), triphenyltin (TPT), monoctyltin (MOT), dioctyltin (DOT) and trioctyltin (TOT) - were quantified in the gastropod Nassarius reticulatus, in the mussel Mytilus galloprovincialis and in sediments. Imposex (imposition of male characters on females of gonochorist gastropods) in N. reticulatus was additionally used as a biomarker of TBT pollution. Time comparisons show a slight decrease of imposex between 2003 and 2005 probably as a consequence of the EU ban, though in some cases this trend seems to have started earlier since 2000. The fraction of TBT relatively to its metabolites has been decreasing over the last years but still remains high suggesting that there are still recent inputs of this compound into the study area.  相似文献   

Future climate impacts on the hydrology of headwater streams in the Amazon River Basin: Implications for migratory goliath catfishes     

Dongmei Feng  Roozbeh Raoufi  Edward Beighley  John M. Melack  Michael Goulding  Ronaldo B. Barthem  Eduardo Venticinque  Carlos Cañas  Bruce Forsberg  Mino Viana Sorribas 《水文研究》2020,34(26):5402-5416

Climate-driven alterations of hydro-meteorological conditions can change river flow regimes and potentially affect the migration behaviour of fishes and the productivity of important fisheries in the Amazon basin, such as those for the continental-scale migratory goliath catfishes (Brachyplatystoma, Pimelodidae). In this study, we investigated hydrologic responses to climate change using a hydrologic model forced with climate inputs, which integrate historical (2001–2010) observations and general circulation model (GCM) projections under the emission scenario Representative Concentration Pathway 8.5. We developed an empirical model to characterize future (2090–2099) climate-change impacts on goliath catfish spawning migrations as a function of river flow depth dynamics at the upstream elevational limit of spawning (250 m) in headwater basins of the Amazon. The model results revealed spatially variable impacts of climate change on the catfish spawning migrations. The Marañón, Ucayali, Juruá, Purus, and Madeira basins had a predicted increase in the annual mean (3–8%) and maximum (1.1–4.9%) spawning migration rate (i.e., the fraction of fish that migrate to the spawning grounds in a day), mainly due to the lengthened rising phase of flow-driven migratory events during wet seasons. The Caquetá-Japurá, Putumayo-Içá, Napo, and Blanco rivers had predicted decreases (3–7%) in the mean migration rate because of decreases in the length of the rising season of flow depth and the frequency of migratory events. The predicted timing of fish spawning migrations (quantified by the temporal centroid of migration rates) was delayed by 7–10 days in the west-central and southwest regions and was 8 days earlier in the northwest and northcentral areas, due to changes in the onset of the rising season. We established a river depth baseline that controls the onset of goliath catfish spawning migration. This depth varies between 0.9–5.6 m across study sites. We found that the estimated depth baseline was most sensitive to uncertainties in river width and cross-sectional channel shape. These results may help inform sustainable adaptation strategies for ecosystem conservation and local fisheries management in the Amazon basin.  相似文献   

Factors driving the biogeochemical budget of the Amazon River and its statistical modelling     

Vincent Bustillo  Reynaldo Luiz Victoria  Jose Mauro Sousa de Moura  Daniel de Castro Victoria  Andre Marcondes Andrade Toledo  Erich Collicchio 《Comptes Rendus Geoscience》2011,343(4):261-277

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Ground motion scenarios consistent with probabilistic seismic hazard disaggregation analysis. Application to Mainland Portugal     

Maria Luísa Sousa  Alfredo Campos Costa 《Bulletin of Earthquake Engineering》2009,7(1):127-147

Probabilistic seismic hazard for Mainland Portugal was re-evaluated in order to perform its disaggregation. Seismic hazard was disaggregated considering different spaces of random variables, namely, univariate conditional hazard distributions of M (magnitude), R (source-to-site distance) and ε (deviation of ground motion to the median value predicted by an attenuation model), bivariate conditional hazard distributions of M–R and X–Y (seismic source latitude and longitude) or multivariate conditional hazard distributions of M–R–ε and M–(X–Y)–ε. The main objective of the present work was achieved, as it was possible, based on the modal values of the above mentioned distributions, to characterize the scenarios that dominate some seismic hazard levels of the 278 Mainland Portuguese counties. In addition, results of 4D disaggregation analysis, in M–(X–Y)–ε, pointed out the existence of one geographic location shared by the dominant scenario of most analyzed counties, especially for hazard levels correspondent to high return periods. Those dominant scenarios are located offshore at a distance of approximately 70 km WSW of S. Vicente cape. On the other hand, the lower the return period the higher is the number of modal scenarios in the neighbourhood of the analyzed site. One may conclude that modal scenarios reproduce hazard target values in each site with great accuracy enabling the applications derived from those scenarios (e.g. loss evaluation) to be associated to a hazard level exceedance probability.  相似文献   

PS-InSAR processing methodologies in the detection of field surface deformation—Study of the Granada basin (Central Betic Cordilleras,southern Spain)     

Joaquim J. Sousa  Antonio M. Ruiz  Ramon F. Hanssen  Luisa Bastos  Antonio J. Gil  Jesús Galindo-Zaldívar  Carlos Sanz de Galdeano 《Journal of Geodynamics》2010,49(3-4):181-189

Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms.Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian–African plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates are in the order of ～1 mm/yr, which are at the feasibility limit of current InSAR techniques.In order to evaluate whether, under these conditions, InSAR techniques can still be used to monitor deformations we have applied and compared two PS-InSAR approaches: DePSI, the PS-InSAR package developed at Delft University of Technology (TU Delft) and StaMPS (Stanford Method for Persistent Scatterers) developed at Stanford University. Ground motion processes have been identified for the first time in the study area, the most significant process being a subsidence bowl located at the village of Otura.The idea behind this comparative study is to analyze which of the two PS-InSAR approaches considered might be more appropriate for the study of specific areas/environments and to attempt to evaluate the potentialities and benefits that could be derived for the integration of those methodologies.  相似文献   

Strontium isotope zoning in garnet: implications for metamorphic matrix equilibration,geochronology and phase equilibrium modelling     

J. Sousa  M. J. Kohn  M. D. Schmitz  C. J. Northrup  F. S. Spear 《Journal of Metamorphic Geology》2013,31(4):437-452

In principle, garnet growth rates may be calculated from ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr measurements in garnet subsamples and the surrounding rock matrix. Because of low Rb/Sr, garnet should passively record the matrix decay of ⁸⁷Rb to ⁸⁷Sr as a progressive increase in ⁸⁷Sr/⁸⁶Sr from core to rim. This concept was tested by collecting Rb‐Sr data for five garnet grains from four major orogenic belts: eastern Vermont (c. 380 Ma), western New Hampshire (c. 320 Ma), southern Chile (c. 75 Ma) and northwestern Italy (c. 35 Ma). Both normal Sr isotope zoning (increasing ⁸⁷Sr/⁸⁶Sr from core to rim) and inverse Sr zoning (decreasing ⁸⁷Sr/⁸⁶Sr from core to rim) were observed. Garnet and matrix isotope data commonly yielded grossly inaccurate model ages. Incomplete Rb and Sr equilibration among matrix minerals is invoked to explain the deviations between theoretical v. measured zoning patterns and the age disparities. Initially, the reactive matrix is dominated by rapidly equilibrating Rb‐rich mica, which imparts high ⁸⁷Sr/⁸⁶Sr values in garnet cores. Progressive participation of slower equilibrating Sr‐rich plagioclase buffers or even reduces ⁸⁷Sr/⁸⁶Sr, possibly leading to flat or decreasing ⁸⁷Sr/⁸⁶Sr from garnet cores to rims. Unusually high ⁸⁷Sr/⁸⁶Sr in garnet in combination with bulk matrix compositions causes erroneously young apparent ages, so metamorphic ages, growth rates, and associated heating and loading rates are likely suspect. Although Rb‐Sr may be the most susceptible because of the profound disparities between mica and feldspar, zircon reactivity might influence the Lu‐Hf system by up to a few per cent. The Sm‐Nd system seems generally immune to these effects. Pseudosection analysis and conventional garnet geochronology, which presume complete matrix equilibration during metamorphism, may require modification to account for differences between whole‐rock v. reactive matrix compositions.  相似文献   

The impact of shrimp farming effluent on bacterial communities in mangrove waters, Ceará, Brazil     

Sousa OV  Macrae A  Menezes FG  Gomes NC  Vieira RH  Mendonça-Hagler LC 《Marine pollution bulletin》2006,52(12):1725-1734

The effects of shrimp farm effluents on bacterial communities in mangroves have been infrequently reported. Classic and molecular biology methods were used to survey bacterial communities from four mangroves systems. Water temperature, salinity, pH, total heterotrophic bacteria and maximum probable numbers of Vibrio spp. were investigated. Genetic profiles of bacterial communities were also characterized by polymerase chain reaction (PCR) amplification of eubacterial and Vibrio 16S rDNA using denaturing gradient gel electrophoresis (DGGE). Highest heterotrophic counts were registered in the mangrove not directly polluted by shrimp farming. The Enterobacteriaceae and Chryseomonas luteola dominated the heterotrophic isolates. Vibrio spp. pathogenic to humans and shrimps were identified. Eubacterial genetic profiles suggest a shared community structure independent of mangrove system. Vibrio genetic profiles were mangrove specific. Neither microbial counts nor genetic profiling revealed a significant decrease in species richness associated with shrimp farm effluent. The complex nature of mangrove ecosystems and their microbial communities is discussed.  相似文献   

On mode conversion and wave reflection in magnetic Ap stars     

S. G. Sousa  M. S. Cunha 《Monthly notices of the Royal Astronomical Society》2008,386(1):531-542

We investigate the effect of a strong large-scale magnetic field on the reflection of high-frequency acoustic modes in rapidly oscillating Ap stars. To that end, we consider a toy model composed of an isothermal atmosphere matched on to a polytropic interior and determine the numerical solution to the set of ideal magnetohydrodynamic equations in a local plane-parallel approximation with constant gravity. Using the numerical solution in combination with approximate analytical solutions that are valid in the limits where the magnetic and acoustic components are decoupled, we calculate the relative fraction of energy flux that is carried away in each oscillation cycle by running acoustic waves in the atmosphere and running magnetic waves in the interior. For oscillation frequencies above the acoustic cut-off, we show that most energy losses associated with the presence of running waves occur in regions where the magnetic field is close to vertical. Moreover, by considering the depth dependence of the energy associated with the magnetic component of the wave in the atmosphere we show that a fraction of the wave energy is kept in the oscillation every cycle. For frequencies above the acoustic cut-off frequency, such energy is concentrated in regions where the magnetic field is significantly inclined in relation to the local vertical. Even though our calculations were aimed at studying oscillations with frequencies above the acoustic cut-off frequency, based on our results we discuss what results may be expected for oscillations of lower frequency.  相似文献   

Exploration and decision-making in geotechnical engineering – a case study     

Rita Sousa  Karim S. Karam  Ana Laura Costa 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(1):129-145

ABSTRACT

The paper presents methodologies for exploration planning under uncertain conditions based on virtual exploration and Bayesian updating. The process starts with site characterization using existing information to produce geologic profiles. Initial distributions of cost and time are obtained with a Bayesian network model that optimizes the construction strategy for particular geologic conditions. This is followed by the unique step to determine with a “virtual exploration” if additional exploration (e.g. borings) is warranted, and if so, where it should be best done. All this is then applied to the planned Abu Dhabi subway tunnels providing the transportation planners with necessary information for planning and design.  相似文献