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121.
Surendra P. Verma Sanjeet K. Verma Elson P. Oliveira 《International Geology Review》2015,57(11-12):1365-1388
Fifty-five new multi-dimensional diagrams, mostly based on log-ratio transformations, were used to decipher tectonic settings for 17 cases of Precambrian belts in Canada, the USA, Poland, Finland, Jordan, Democratic Republic of Congo and Zambia, China, and India. The results of different sets of diagrams for basic-ultrabasic, intermediate, and acid magmas were generally internally consistent. Possible reasons for some inconsistencies may be related to the use of a sample group of mixed ages because of their uncertainties, extreme element mobility caused by metamorphism especially of high-grade type, analytical data quality, different petrogenetic processes for basic to acid magmas such as mantle versus crustal origin, and some deficiencies that still exist in the multi-dimensional diagrams. To partly overcome the last problem, one new multi-dimensional diagram is proposed and used to discriminate mid-ocean ridge and oceanic plateau settings. 相似文献
122.
Sanjeet K. Verma Elson P. Oliveira Surendra P. Verma 《International Geology Review》2015,57(11-12):1566-1581
Multidimensional discrimination diagrams (2006–2011) for basic and ultrabasic igneous rocks were applied to Precambrian rock suites from the Amazonian and São Francisco cratons, and the Tocantins Province, Brazil, to infer their possible tectonic settings. The chosen study cases in the Amazonian craton include the ca. 3.0 Ga metabasalts of the Identidade greenstone belt, 1.87–1.80 Ga Parauapebas anorogenic basalt-rhyolite dikes, 1.86–1.82 Ga Rio Branco anorogenic gabbro-basalt association, ca. 1.76–1.74 Ga Aripuanã and Teles Pires intracratonic basalt-felsic volcanic associations, and 1.76–1.74 Ga Jamari and 1.60–1.53 Ga Serra da Providência arc-related gabbroic rocks. In the São Francisco craton, we selected 1.48 Ga arc-related amphibolites of the Rio Capim greenstone belt, continental mafic dikes of Uauá (2.6 Ga), Curaçá and Chapada Diamantina (1.5 Ga), and Espinhaço (ca. 1.0 Ga). In the Tocantins Province, ca. 3.0 Ga komatiites associated with oceanic basalts of the Crixás and Guarinos greenstone belts were studied. The application of the diagrams generally provided consistent results with the authors’ proposed tectonic settings based on field relationships and geochemical data. The exceptions are some within-plate (continental) mafic dikes and basalts for which our diagrams do not work well. For comparison, we also used two ternary and two bivariate traditional discrimination diagrams for the data from the Amazonian craton, whose results were poorer than the newer multidimensional diagrams. 相似文献
123.
In order to perform a good pulse compression, the conventional spike deconvolution method requires that the wavelet is stationary. However, this requirement is never reached since the seismic wave always suffers high‐frequency attenuation and dispersion as it propagates in real materials. Due to this issue, the data need to pass through some kind of inverse‐Q filter. Most methods attempt to correct the attenuation effect by applying greater gains for high‐frequency components of the signal. The problem with this procedure is that it generally boosts high‐frequency noise. In order to deal with this problem, we present a new inversion method designed to estimate the reflectivity function in attenuating media. The key feature of the proposed method is the use of the least absolute error (L1 norm) to define both the data and model error in the objective functional. The L1 norm is more immune to noise when compared to the usual L2 one, especially when the data are contaminated by discrepant sample values. It also favours sparse reflectivity when used to define the model error in regularization of the inverse problem and also increases the resolution, since an efficient pulse compression is attained. Tests on synthetic and real data demonstrate the efficacy of the method in raising the resolution of the seismic signal without boosting its noise component. 相似文献
124.
D. Labat J.-C. Espinoza J. Ronchail G. Cochonneau E. de Oliveira J.C. Doudou 《水文科学杂志》2013,58(6):1081-1091
Abstract The discharge variability of the main rivers that drain the Guyana Shield is analysed over the last 50 years using cross-wavelet, coherence and composite analysis involving oceanic and atmospheric variables. We highlight the overall hydro-climatological homogeneity of this region that allowed us to focus on the longest discharge time series available. Therefore, a wavelet cross-analysis was carried out between monthly and seasonal Maroni River discharge at the Langa Tabiki station and selected climate indices. This confirms a strong relationship between the hydrology of the Guyana Shield and the Pacific sea-surface temperature (SST) fluctuations. There is evidence of intermittent influence, of between inter-annual and near decadal scales, of the Atlantic SST fluctuations, in particular around 1970 and 1990. Finally, we show that the links between oceanic regions and high discharge in the rivers of Guyana are realized through the reinforcement of the Walker and Hadley cells between the Amazon and the adjacent oceans and through decreased trade winds and monsoon flux that favour the persistence of humidity over the Guyana Shield. Editor Z.W. Kundzewicz; Associate editor D. Hughes Citation Labat, D., Espinoza, J.-C., Ronchail, J., Cochonneau, G., de Oliveira, E., Doudou, J.C. and Guyot, J.-L., 2012. Fluctuations in the monthly discharge of Guyana Shield rivers, related to Pacific and Atlantic climate variability. Hydrological Sciences Journal, 57 (6), 1081–1091. 相似文献
125.
da Silveira Lucas Cardoso de Oliveira Amauri Pereira Sánchez Maciel Piñero Codato Georgia Ferreira Maurício Jonas Marques Filho Edson Pereira Božnar Marija Zlata Mlakar Primož 《Boundary-Layer Meteorology》2022,185(2):161-195
Boundary-Layer Meteorology - Statistical properties of turbulence, specifically variances of velocity components, temperature, water vapor, and carbon dioxide densities, are observationally... 相似文献
126.
Pinheiro Maria Eduarda O. de Oliveira Pablo E. S. Acevedo Otávio C. 《Boundary-Layer Meteorology》2022,183(1):79-96
Boundary-Layer Meteorology - Vertical profiles of temperature, water vapour, and carbon dioxide ( $$\mathrm {CO}_{2}\,$$ ) densities are analyzed, together with the respective turbulent fluxes of... 相似文献
127.
José Francirlei Oliveira Michel Brossard Pedro Rodolfo Siqueira Vendrame Stanislas Mayi III Edemar Joaquim Corazza Robélio Leandro Marchão Maria de Fátima Guimarães 《Comptes Rendus Geoscience》2013,345(11-12):446-453
Vis–NIR spectroscopy is nowadays presented as a possible routine method for soil sample analysis. However, there is still no consensus on which is the best multivariate statistical method to use. We propose to use principal component analysis to complete the spectral data treatment. The soil samples came from a pedological cover made up of red–yellow Latosols: 88 samples of 11 soil profiles on four toposequences were collected; clay, organic matter, silica, iron, aluminum and titanium total contents were determined; the contents of goethite, hematite, gibbsite, and kaolinite were calculated. Diffuse reflectance Vis–NIR spectroscopy at wavelengths from 400 to 2400 nm combined with principal component analysis (PCA) was sufficiently sensitive to discriminate different Latosols. Wavelengths of 700 nm and 2200 to 2300 nm were influenced by content ratios of organic matter and iron oxides (700 nm), and kaolinite and gibbsite absorption (2200 and 2300 nm). The spectral responses were affected not only by the content of these constituents, but also by the composition of the minerals, so that the same class of Latosol may have different or similar spectral responses. The role of microaggregation is discussed. 相似文献
128.
Ana Rita Oliveira Cristina Branquinho Maria Pereira Amílcar Soares 《Mathematical Geosciences》2013,45(4):437-452
This paper presents a study in which the lung cancer risk in males was characterized based on a simulation model of mortality rates. Block sequential simulation of mortality rates, measured in counties of different sizes, was implemented and applied to a normal grid of continental Portugal with high spatial resolution. The uncertainty in the mortality rate measurements, directly related to differences in the population size of each county, was integrated in a block direct sequential simulation through Poisson kriging of local means and variances. Three age groups were examined: 50–59, 60–69, and 70–79 years. After the continuous geographic patterns of lung cancer risk were obtained, factors potentially associated with the main areas of risk were analyzed for southern Portugal. Thus, a defined class of land use and dry weather events, related to airborne particulate matter, were found to be associated with high-risk areas, resulting in high local spatial correlation patterns in all three age groups. 相似文献
129.
M. F. Araújo J. -M. Jouanneau P. Valrio T. Barbosa A. Gouveia O. Weber A. Oliveira A. Rodrigues J. M. A. Dias 《Progress in Oceanography》2002,52(2-4)
The northern Portuguese coastal zone is drained by large Iberian rivers, along which there is intensive industrial, agricultural and urban activity. Offshore of the two main river basins of the Douro and Minho, two fine-grained sedimentary formations can be characterised. A geochemical study of this sediment cover has been performed focussing in particular on the fine deposits and the adjacent estuaries. The chemical composition of superficial sediments collected from the northern Portuguese shelf and from the river basins of the Minho and Douro rivers was determined for major, minor and trace elements; the rare earth elements (REE) composition was also determined in selected samples. Statistical analyses of these data for the shelf sediments allow us to identify elements with similar behaviours and the different sediment types along the shelf, and to evaluate of their origins. Downcore profiles of the chemical composition of the fine sediments reveal no evidence for changes induced by recent human activities. To assess the influence of the rivers on the fine sedimentary formations, the elemental distribution patterns of selected sediments have been compared with the estuarine sediments. Lithogenic elements composition normalised to Al and the shale normalised REE distributions showed there are similarities between the Douro River sediments and the sediment composition of the Douro and Galicia mud patches. However, the Galicia mud field showed no relationship in its chemical composition to sediments derived from the Minho River. Nor was any evidence for heavy metal contamination originating from the Douro estuary detected in anthropogenic element/Al ratios in the shelf sediments. This may be because of processes associated with resuspension, complexation and bioturbation that occur during sediment transport and deposition. Nevertheless, the Douro River seems to be the main continental source of fine sediments being deposited on the northern Portuguese shelf. 相似文献
130.
J. M. Jouanneau O. Weber T. Drago A. Rodrigues A. Oliveira J. M. A. Dias C. Garcia S. Schmidt J. L. Reyss 《Progress in Oceanography》2002,52(2-4)
Thus study is based on 31 box-core samples collected mainly from the mud-patches of the Galician and North-Portuguese shelf. Each of these cores, some decimetres in length, have been described, radiographied and sampled each centimetre for grain-size analysis and measurement of the particulate organic carbon (Corg) content. 210Pb excess profiles have been measured using gamma spectrometry, which, combined with the analysis of the vertical variations of the sedimentary facies, have allowed estimates of sedimentation rates. These rates were found to vary between 0.05 and 0.40 cm yr−1. Considering the latitudinal variation of sedimentation rates around the 100m contour, we note that the maximum rates occurred off the Douro estuary in the southern sector and also near the Galician rias to the north. The organic content (Corg) of sediments varied between 0.4 and 2%. Latitudinally Corg showed a decrease from the South to the North. These results coupled with the sedimentary map (see Dias, Gonzalez, Garcia & Diaz del Rio, 2001) have permitted us to establish the detrital mass budget and an inventory of Corg burial. 相似文献