Geochemistry and petrology of the jequie granulitic complex (Brazil): an archean basement complex     

G. P. Sighinolfi  M. C. H. Figueredo  W. S. Fyfe  B. I. Kronberg  M. A. F. Tanner Oliveira 《Contributions to Mineralogy and Petrology》1982,78(3):263-271

The Jequie granulitic complex is part of the extensive high-grade metamorphic terrain located within the Sao Francisco craton of northeastern Brazil. Some Jequie rocks appear to have been formed in the middle Archean ( 3.1 Ga) from preexisting sialic crust. The dominant mineral composition of these rocks is quartz-microcline-plagioclase-hyperstene and occurs over an extensive area ( 2,000 km²).Scattered enrichment of normal granites with many minor elements (e.g. Rb, Y, Zr, Nb, Ba, REE), and the non-depletion of other elements (e.g. Cs, U), normally considered mobile during granulite facies metamorphism, must lead either to the reconsideration of regional metasomatism subsequent to granulite facies metamorphism, or at least raise some doubts about common wisdom concerning the distribution of heat-producing elements at depth. The region includes large-scale thrust structures, which could play a part in influencing high-level emplacement of the rocks and their regional metasomatism and structures.  相似文献   

Extreme values and meteorology     

J. Tiago de Oliveira 《Theoretical and Applied Climatology》1986,37(4):184-193

Summary The basic ideas of univariate extremes and some applications are described in the paper; some references are made to multivariate extremes and stochastic processes of extremes.

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Zusammenfassung Es werden einige grundlegende Ideen zu univariaten Extremen und ihren Anwendungen beschrieben. Multivariate Extreme und stochastische Prozesse von Extremen werden ebenfalls besprochen.

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With 4 Figures  相似文献   

Temperature depression in the lowland tropics in glacial times     

Paul A. Colinvaux  Kam-Biu Liu  Paulo de Oliveira  Mark B. Bush  Michael C. Miller  Mirriam Steinitz Kannan 《Climatic change》1996,32(1):19-33

Equatorial air temperatures at low elevations in the New World tropics are shown by pollen and other data to have been significantly lowered in long intervals of the last glaciation. These new data show that long recognized evidence for cooling at high elevations in the tropics were symptomatic of general tropical cooling and that they did not require appeal to altered lapse rates or other special mechanisms to be made to conform with conclusions that equatorial sea surface temperatures (SSTs) were scarcely changed in glacial times. The new data should be read in conjunction with recent findings that Caribbean (SSTs) were lowered in the order of 5 ° C, contrary to previous interpretations. Thus these accumulating data show that low latitudes as well as high were cooled in glaciations. In part the earlier failure to find evidence of low elevation cooling in the lowland tropics resulted from the data being masked by strong signals for aridity given by old lake levels in parts of Africa and elsewhere. Global circulation models used to predict future effects of greenhouse warming must also be able to simulate the significant cooling of the large tropical land masses at glacial times with reduced greenhouse gas concentrations. Plants and animals of the Amazon forest and similar ecosystems are able to survive in wide ranges of temperatures, CO₂ concentrations, and disturbance, though associations change constantly.  相似文献   

Geology and geophysics as successful tools in the discovery of the Lagoa Salgada Orebody (Sado Tertiary Basin – Iberian Pyrite Belt), Grândola, Portugal     

V. Oliveira  J. Matos  M. Bengala  N. Silva  P. Sousa  L. Torres 《Mineralium Deposita》1997,33(1-2):170-187

Gravimetry was the main exploration method used in this high risk area to the north of the Grândola fault, in the Iberian Pyrite Belt (IPB). It showed several targets, among which the Valverde-Lagoa Salgada area stood out. Here, in August 1992, a polymetallic massive sulphide orebody was found, named Lagoa Salgada. According to the geological characteristics of the area and to the nature of the surveyed targets, other exploration techniques were used, namely: geology, magnetometry, resistivity, electrical sounding, magneto-telluric, seismic and mechanical drilling. The deposit was found under a Tertiary cover, 128?m in depth, complete with a 15?m thick gossan, caused by paleoalteration, with a supergene enrichment zone. This gossan gave way to massive sulphides, with intersections, at times, exceeding 60?m. They are limited towards the footwall by an important fault with strong associated kaolinization, which is interpreted as a reverse fault, placed on the inverse limb of an anticlinal structure. Throughout the deposit, the chemical composition of the mineralization showed great variation reaching significant values of Zn, Pb, Sn, Cu, As, Hg, Sb, Cd, Au and Ag. In the initial phase the deposit has an estimated tonnage of 5?Mt. It is related to a large gravity anomaly with the general orientation NW-SE, which was investigated by 15 boreholes made by the Instituto Geológico e Mineiro. The drilling cut an important volcanic centre of an acid to intermediate nature, around which intense hydrothermal activity was associated with contemporaneous sulphide mineralization. The gravity anomaly has two nuclei, a NW and a central one, about 450?m apart, where a pyrite orebody with polymetallic sulphides and stockwork sulphide mineralization are developed. This discovery led to an extensive exploration project that confirmed the mining potentialities of the NW sector of the IPB, to the north of Grândola fault, where previously no polymetallic sulphide occurrences were known.  相似文献   

Petrogenesis of the late proterozoic curaçá mafic dyke swarm,Brazil: Asthenospheric magrnatisrn associated with continental collision     

Dr. E. P. Oliveira  J. Tarney 《Mineralogy and Petrology》1995,53(1-3):27-48

Summary The late Proterozoic Curaçâ mafic dyke swarm is one of the more alkaline swaams of the Brazilian Precambrian. Intea-dyke chemical variations are characterised by higher abundances of incompatible elements in dyke margins than in the dyke centres, a feature that may have resulted from flowage differentiation, from progressive evacuation of liquids from zoned magma chambers, or possibly through dynamic melting of an uprising diapir. Inter-dyke chemical differences are best interpreted by different extents of melting of a mantle source with a small modal proportion of garnet. This source was heterogeneous and had the trace element compositions of ocean island basalts with Dupal and non-Dupa' characteristics. The emplacement of the Curaçá dykes from 650–700 Ma may have been facilitated by the extensional tectonics perpendicular to the collision zone between the São Francisco craton and the Pernambuco-Alagoas massif during the evolution of the Sergipano orogen. The energy in the system was insufficient to promote much melting of, or interaction with, the continental lithosphere or overlying crust.

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Petrogenese des jung-proterozoischen mafischen Gangsystems von Curaca, Brasilien: Asthenosphärischer Magmatismus im Zusammenhang mit kontinentaler Kollision

Zusammenfassung Im jung-proterozoischen alkali-betonten mafischen Gangsystem vom Curaca im brasilianischen Präkambrium zeigen chemische Variationen innerhalb eines Ganges höhere Gehalte an inkompatiblen Elementen an den Gangrändern als in den Zentren. Diese Erscheinung könnte auf Differentiation während der Fließbewegungen zurückgehen, aber auch auf schrittweise Entfernung von Schmelzen aus zonierten Magmenkammern, oder möglicherweise auch auf dynamisches Schmelzen eines aufsteigenden Diapirs. Chemische Unterschiede zwischen einzelnen Gängen können am besten durch verschiedene Rate der Aufschmelzung einer Mantelquelle mit einem geringen Modalanteil von Granat erklärt werden. Diese Quelle war heterogen und hatte den Spurenelementgehalt von ozeanischen Inselbasalten mit Dupal und Non-Dupal Charakteristiken. Die Platznahme der Gänge von Curaca hat zwischen 650 und 700 Ma stattgefunden; sie wurde durch Dehnungstektonik senkrecht zu der Kollisionszone zwischen dem Sao Francisco Kraton und dem Pernambuco-Alagoas Massiv, während der Entwicklung des Sergipano Orogens, gefördert. Die im System vorhandene Energie war nicht ausreichend, um umfangreiche Schmelzvorgänge von, oder Interaktion mit der kontinentalen Lithosphäre, oder der überlagernden Kruste zu verursachen.

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With 13 Figures  相似文献   

Calibration of a photoelectric cloud condensation nucleus counter   总被引：1，自引：0，他引：1  

J. C. P. de Oliveira  G. Vali 《Atmospheric Research》1995,38(1-4)

Calibrations were performed for the photodetector output of a static thermal-gradient diffusion chamber by comparing the detector signals with visual counts of the number of droplets developing in the chamber. The calibrations cover the supersaturation range 0.3% to 1 %. For each supersaturation, the CCN concentration was found to be proportional to the detector output. During the activation and growth of droplets, the time of peak signal corresponds well to the time at which droplet count is a maximum within the sample volume. The use of an average output signal over a period bracketing the mean position of the peak is a slightly better measure of droplet concentrations than the peak value. The calibration equations here derived are specific to the CCN counter used to obtain the data. Also, the calibration constants can be expected to be dependent on the type of aerosol which serve as CCN; the limited data so for available show only weak variations in the constants.  相似文献   

Vertical Profiles of Turbulence Parameters in the Thermal Internal Boundary Layer     

Martins  Luís Gustavo N.  Acevedo  Otávio C.  Puhales  Franciano S.  Degrazia  Gervásio A.  Oliveira  Pablo E. S. 《Boundary-Layer Meteorology》2021,179(3):423-446

Boundary-Layer Meteorology - The correct simulation of pollutant dispersion in coastal regions demands understanding the turbulence structure of the thermal internal boundary layer (TIBL), which...  相似文献   

A Surface-Layer Study of the Transport and Dissipation of Turbulent Kinetic Energy and the Variances of Temperature,Humidity and CO$$_$$     

João A. Hackerott  Mostafa Bakhoday Paskyabi  Joachim Reuder  Amauri P. de Oliveira  Stephan T. Kral  Edson P. Marques Filho  Michel dos Santos Mesquita  Ricardo de Camargo 《Boundary-Layer Meteorology》2017,165(2):211-231

We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO\(_2\) content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afternoon and Sunset Turbulence experiment. The consequences of dissipation similarity in the variance transport are also discussed and quantified. The results show that, for the convective atmospheric surface layer, the non-dimensional dissipation terms can be expressed in the framework of Monin–Obukhov similarity theory and are independent of whether the variable is temperature or moisture. The scalar similarity in the dissipation term implies that the characteristic scales of the atmospheric surface layer can be estimated from the respective rate of variance dissipation, the characteristic scale of temperature, and the dissipation rate of temperature variance.  相似文献   

Soil chemical alteration due to slaughterhouse waste application as identified by spectral reflectance in São Paulo State,Brazil: an environmental monitoring useful tool     

José A. M. Demattê  Julianne de Castro Oliveira  Tiago Rodrigues Tavares  Leonardo Ramirez Lopez  Fabrício da Silva Terra  Suzana Romeiro Araújo  Caio Troula Fongaro  Stoécio Malta Ferreira Maia  Francisco Fujita de Castro Mello  Rodnei Rizzo  Simone Vicente  Marco Antonio de Melo Bortolleto  Pedro Henrique Ramos Cerqueira 《Environmental Earth Sciences》2016,75(18):1277

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Assessment of human effects through phosphorus partitioning in sediments from two catchment basins around Guanabara Bay,SE Brazil     

Carlos Marclei Arruda Rangel  José Antônio Baptista Neto  Priscilla Soares de Oliveira  Luciana Gomes Lima  Estefan Monteiro da Fonseca 《Environmental Earth Sciences》2016,75(17):1215

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