22 resultados para Brasilian Amazonia
Resumo:
The creation of Extractive Reserves (RESEX s) emerges from the resistence movement of the forest people and represents an alternative administration of the naturel resources in the from of Conservation Units (UC). From the institutional point of view the RESEX s are UC s of direct use belong of the Brazilian State, which concedes the right of use to resident families through a legal concession, uhich in based an the principle of coadministration between state and community. The use of these areas is based on the paradigm of sustainable development. In the Extractive Reserve of Rio Cajari over time there has been an experience of confliting interests between the big capital and the local population, which led to noticiable changes of lifestyle of the rural extrativist. In this sense the essay Extractive Reserve of Rio Cajari: various aspects of land use and awnership in southem Amapa , wants to analyse the nuances in which the land grabbing happened and how it affected the day to day of life its in habitants
Resumo:
Intense precipitation events (IPE) have been causing great social and economic losses in the affected regions. In the Amazon, these events can have serious impacts, primarily for populations living on the margins of its countless rivers, because when water levels are elevated, floods and/or inundations are generally observed. Thus, the main objective of this research is to study IPE, through Extreme Value Theory (EVT), to estimate return periods of these events and identify regions of the Brazilian Amazon where IPE have the largest values. The study was performed using daily rainfall data of the hydrometeorological network managed by the National Water Agency (Agência Nacional de Água) and the Meteorological Data Bank for Education and Research (Banco de Dados Meteorológicos para Ensino e Pesquisa) of the National Institute of Meteorology (Instituto Nacional de Meteorologia), covering the period 1983-2012. First, homogeneous rainfall regions were determined through cluster analysis, using the hierarchical agglomerative Ward method. Then synthetic series to represent the homogeneous regions were created. Next EVT, was applied in these series, through Generalized Extreme Value (GEV) and the Generalized Pareto Distribution (GPD). The goodness of fit of these distributions were evaluated by the application of the Kolmogorov-Smirnov test, which compares the cumulated empirical distributions with the theoretical ones. Finally, the composition technique was used to characterize the prevailing atmospheric patterns for the occurrence of IPE. The results suggest that the Brazilian Amazon has six pluvial homogeneous regions. It is expected more severe IPE to occur in the south and in the Amazon coast. More intense rainfall events are expected during the rainy or transitions seasons of each sub-region, with total daily precipitation of 146.1, 143.1 and 109.4 mm (GEV) and 201.6, 209.5 and 152.4 mm (GPD), at least once year, in the south, in the coast and in the northwest of the Brazilian Amazon, respectively. For the south Amazonia, the composition analysis revealed that IPE are associated with the configuration and formation of the South Atlantic Convergence Zone. Along the coast, intense precipitation events are associated with mesoscale systems, such Squall Lines. In Northwest Amazonia IPE are apparently associated with the Intertropical Convergence Zone and/or local convection.
Resumo:
The ediacaran plutonic activity related to the Brasilian/Pan-African orogeny is one of the most important geological features in the Borborema Province, represented along its extension by numerous batholiths, stocks, and dikes.The object of this study, the Serra Rajada Granitic Pluton (SRGP), located in the central portion of the Piranhas-Seridó River Domain is an example of this activity. This pluton has been the subject of cartographic, petrographic, geochronological and lithogeochemical studies and its rocks were characterized by two facies. First, the granitic facies were described as monzogranites consisting of K-feldspar, plagioclase (oligoclase - An23-24%), quartz and biotite (main mafic) and opaque minerals such as titanite, allanite, apatite, and zircon as accessories. Alteration minerals are chlorite, white mica and carbonate. Second, the dioritic facies consist of rocks formed by quartz diorite containing plagioclase (dominant mineral phase), quartz and K-feldspar. Biotite and amphibole are the dominant mafic minerals; and titanite, opaque minerals, allanite, zircon and apatite are the accessories. However, previous geological mapping work in the region also identified the presence of other lithostratigraphic units. These were described as gneisses and migmatites with undifferentiated amphibolite lenses related to the Caicó Complex (Paleoproterozoic) and metasedimentary rocks of the Seridó Group (Neoproterozoic) composed of paragneiss with calc-silicate lenses, muscovite quartzite and biotite schist (respectively, the Jucurutu formations, Equador and Seridó), the host rocks for the SRGP rocks. Leucomicrogranite and pegmatite dikes have also been identified, both related to the end of the Ediacaran magmatism and colluvial- eluvial and alluvial deposits related to Neogene and Quaternary, respectively. Lithogeochemical data on the SRGP granite facies, highlighted quite evolved rocks (SiO2 69% to 75%), rich in alkalis (Na2O+K2O ≥ 8.0%), depleted of MgO (≤ 0.45%), CaO (≤ 1.42%) and TiO2 (≤ 0.36%) and moderate levels of Fe2O3t (2.16 to 3.53%). They display transitional nature between metaluminous and peraluminous (predominance of the latter) with sub-alkaline/monzonitic (High K calcium-alkali) affinity. Harker diagrams show negative correlations for Fe2O3t, MgO, and CaO, indicating mafic and plagioclase fractionation. REE spectrum shows enrichment of LREE relative to heavy REE (LaN/YbN = 23.70 to 10.13), with negative anomaly in the Eu (Eu/Eu* = 0.70 to 0.23), suggesting fractionation or accumulation in the feldspars source (plagioclase). Data integration allows to correlate the SRGP rocks with those described as Calcium-Alkaline Suite of equigranular High K. The crystallization conditions of the SRGP rocks were determined from the integration of petrographic and lithogeochemical data. These data indicated intermediate to high conditions of ƒO2 (mineral paragenesis titanite + magnetite + quartz), parent magma saturated in H2O (early biotite crystallization), tardi-magmatic processes of fluids rich in ƒCO2, H2O and O2 causing part of the mineral assembly to change (plagioclase carbonation and saussuritization, biotite chloritization and opaques Sphenitization). Thermobarometrical conditions were estimated based on geochemical parameters (Zr and P2O5) and CIPW normative minerals, with results showing the liquidus minimum temperature of about800°C and the solidus temperature of approximately 700°C. The final/minimum crystallization pressure are suggested to be between 3 and 5 Kbar. The presence of zoned minerals (plagioclase and allanite) associated with lithogeochemical data in bi-log diagrams for Rb vs. Ba and Rb vs. Sr suggest the role of fractional crystallization as the dominant process in the magmatic evolution of SRGP. U-Pb Geochronological and Sm-Nd isotope studies indicated, respectively, the crystallization age of biotite monzogranite as 557 ± 13 Ma, with TDM model age of 2.36 Ga, and εNd value of -20.10 to the crystallization age, allowing to infer paleoproterozoic crustal source for the magma.
Resumo:
The ediacaran plutonic activity related to the Brasilian/Pan-African orogeny is one of the most important geological features in the Borborema Province, represented along its extension by numerous batholiths, stocks, and dikes.The object of this study, the Serra Rajada Granitic Pluton (SRGP), located in the central portion of the Piranhas-Seridó River Domain is an example of this activity. This pluton has been the subject of cartographic, petrographic, geochronological and lithogeochemical studies and its rocks were characterized by two facies. First, the granitic facies were described as monzogranites consisting of K-feldspar, plagioclase (oligoclase - An23-24%), quartz and biotite (main mafic) and opaque minerals such as titanite, allanite, apatite, and zircon as accessories. Alteration minerals are chlorite, white mica and carbonate. Second, the dioritic facies consist of rocks formed by quartz diorite containing plagioclase (dominant mineral phase), quartz and K-feldspar. Biotite and amphibole are the dominant mafic minerals; and titanite, opaque minerals, allanite, zircon and apatite are the accessories. However, previous geological mapping work in the region also identified the presence of other lithostratigraphic units. These were described as gneisses and migmatites with undifferentiated amphibolite lenses related to the Caicó Complex (Paleoproterozoic) and metasedimentary rocks of the Seridó Group (Neoproterozoic) composed of paragneiss with calc-silicate lenses, muscovite quartzite and biotite schist (respectively, the Jucurutu formations, Equador and Seridó), the host rocks for the SRGP rocks. Leucomicrogranite and pegmatite dikes have also been identified, both related to the end of the Ediacaran magmatism and colluvial- eluvial and alluvial deposits related to Neogene and Quaternary, respectively. Lithogeochemical data on the SRGP granite facies, highlighted quite evolved rocks (SiO2 69% to 75%), rich in alkalis (Na2O+K2O ≥ 8.0%), depleted of MgO (≤ 0.45%), CaO (≤ 1.42%) and TiO2 (≤ 0.36%) and moderate levels of Fe2O3t (2.16 to 3.53%). They display transitional nature between metaluminous and peraluminous (predominance of the latter) with sub-alkaline/monzonitic (High K calcium-alkali) affinity. Harker diagrams show negative correlations for Fe2O3t, MgO, and CaO, indicating mafic and plagioclase fractionation. REE spectrum shows enrichment of LREE relative to heavy REE (LaN/YbN = 23.70 to 10.13), with negative anomaly in the Eu (Eu/Eu* = 0.70 to 0.23), suggesting fractionation or accumulation in the feldspars source (plagioclase). Data integration allows to correlate the SRGP rocks with those described as Calcium-Alkaline Suite of equigranular High K. The crystallization conditions of the SRGP rocks were determined from the integration of petrographic and lithogeochemical data. These data indicated intermediate to high conditions of ƒO2 (mineral paragenesis titanite + magnetite + quartz), parent magma saturated in H2O (early biotite crystallization), tardi-magmatic processes of fluids rich in ƒCO2, H2O and O2 causing part of the mineral assembly to change (plagioclase carbonation and saussuritization, biotite chloritization and opaques Sphenitization). Thermobarometrical conditions were estimated based on geochemical parameters (Zr and P2O5) and CIPW normative minerals, with results showing the liquidus minimum temperature of about800°C and the solidus temperature of approximately 700°C. The final/minimum crystallization pressure are suggested to be between 3 and 5 Kbar. The presence of zoned minerals (plagioclase and allanite) associated with lithogeochemical data in bi-log diagrams for Rb vs. Ba and Rb vs. Sr suggest the role of fractional crystallization as the dominant process in the magmatic evolution of SRGP. U-Pb Geochronological and Sm-Nd isotope studies indicated, respectively, the crystallization age of biotite monzogranite as 557 ± 13 Ma, with TDM model age of 2.36 Ga, and εNd value of -20.10 to the crystallization age, allowing to infer paleoproterozoic crustal source for the magma.
Resumo:
The Serra do Caramuru and Tapuio stocks, located in the extreme NE of Rio Piranhas-Seridó Domain (RN), are representative of the Ediacaran-Cambrian magmatism, an important magmatic feature of the Brasilian / Panafrican orogeny of the Borborema Province. These bodies are lithologically similar, intrusive in paleoproterozoic gneiss embasement, being separated by a thin belt of mylonitic orthogneiss. The field relations show a magmatic stratigraphy initiated by dioritic facies that coexists with the porphyritic granitic and equigranular granitic I facies, and less frequently with equigranular granitic II facies. These rocks are crosscut by late granitic dykes and sheets with NE-SW / NNE-SSW orientation. The dioritic facies (diorite, quartz diorite, quartz monzodiorites, tonalite and granodiorite) is leucocratic to melanocratic, rich in biotite and hornblende. The granitic facies are hololeucocratic to leucocratic, and have biotite ± hornblende. Petrographic and geochemical (whole rock) data, especially from Serra do Caramuru pluton, suggest fractionation of zircon, apatite, clinopyroxene (in diorites), opaque minerals, titanite, biotite, hornblende, allanite, plagioclase, microcline and garnet (in dykes). The behavior of trace elements such as Zr, La and Yb indicates that the dioritic magma does not constitute the parental magma for the granitic facies. On the other hand, the granitic facies seems to be cogenetic to each other, displaying differentiation trends and very similar rare earth elements (REE) spectra [12.3≤(La/Yb)N≤190.8; Eu/Eu*=0.30-0.68]. Field relationships and REE patterns [6.96≤(La/Yb)N≤277.8; Eu/Eu*=0.18-0.58] demonstrate that the granitic dykes and sheets are not cogenetically related to the Serra do Caramuru magmatism. The dioritic facies is metaluminous (A/CNK = 0.88-0.74) and shoshonitic, whereas the granitic ones are metaluminous to peraluminous (A/CNK = 1.08-0.93) and high potassium calc-alkaline. Dykes and sheets are strictly peraluminous (A/CNK = 1.01-1.04). Binary diagrams relating compatible and incompatible trace elements and microtextures indicate the fractional crystallization as the dominant mechanism of magmatic evolution of the various facies. The Serra do Caramuru and Tapuio stocks have well preserved magmatic fabric, do not show metamorphic minerals and are structurally isotropic, showing crosscutting contact with the ductile fabric of the basement. These observations lead to interpretate a stage of relative tectonic stability, consistent with the orogenic relaxation period of the Brasiliano / Pan-African orogeny. Chemical plots involving oxides and trace elements indicate late to post-collisional emplacement. In this context, the assumed better mechanism to describe the stocks emplacement within an extensional T Riedel joint, with ENE-WSW extensional vector. The U-Pb zircon age of 553 ± 10 Ma allows correlating the Serra do Caramuru magmatism to the group of post-collisional bodies, equigranular high potassium calc-alkaline granites of the NE of Rio Piranhas-Seridó Domain.
Resumo:
The Serra do Caramuru and Tapuio stocks, located in the extreme NE of Rio Piranhas-Seridó Domain (RN), are representative of the Ediacaran-Cambrian magmatism, an important magmatic feature of the Brasilian / Panafrican orogeny of the Borborema Province. These bodies are lithologically similar, intrusive in paleoproterozoic gneiss embasement, being separated by a thin belt of mylonitic orthogneiss. The field relations show a magmatic stratigraphy initiated by dioritic facies that coexists with the porphyritic granitic and equigranular granitic I facies, and less frequently with equigranular granitic II facies. These rocks are crosscut by late granitic dykes and sheets with NE-SW / NNE-SSW orientation. The dioritic facies (diorite, quartz diorite, quartz monzodiorites, tonalite and granodiorite) is leucocratic to melanocratic, rich in biotite and hornblende. The granitic facies are hololeucocratic to leucocratic, and have biotite ± hornblende. Petrographic and geochemical (whole rock) data, especially from Serra do Caramuru pluton, suggest fractionation of zircon, apatite, clinopyroxene (in diorites), opaque minerals, titanite, biotite, hornblende, allanite, plagioclase, microcline and garnet (in dykes). The behavior of trace elements such as Zr, La and Yb indicates that the dioritic magma does not constitute the parental magma for the granitic facies. On the other hand, the granitic facies seems to be cogenetic to each other, displaying differentiation trends and very similar rare earth elements (REE) spectra [12.3≤(La/Yb)N≤190.8; Eu/Eu*=0.30-0.68]. Field relationships and REE patterns [6.96≤(La/Yb)N≤277.8; Eu/Eu*=0.18-0.58] demonstrate that the granitic dykes and sheets are not cogenetically related to the Serra do Caramuru magmatism. The dioritic facies is metaluminous (A/CNK = 0.88-0.74) and shoshonitic, whereas the granitic ones are metaluminous to peraluminous (A/CNK = 1.08-0.93) and high potassium calc-alkaline. Dykes and sheets are strictly peraluminous (A/CNK = 1.01-1.04). Binary diagrams relating compatible and incompatible trace elements and microtextures indicate the fractional crystallization as the dominant mechanism of magmatic evolution of the various facies. The Serra do Caramuru and Tapuio stocks have well preserved magmatic fabric, do not show metamorphic minerals and are structurally isotropic, showing crosscutting contact with the ductile fabric of the basement. These observations lead to interpretate a stage of relative tectonic stability, consistent with the orogenic relaxation period of the Brasiliano / Pan-African orogeny. Chemical plots involving oxides and trace elements indicate late to post-collisional emplacement. In this context, the assumed better mechanism to describe the stocks emplacement within an extensional T Riedel joint, with ENE-WSW extensional vector. The U-Pb zircon age of 553 ± 10 Ma allows correlating the Serra do Caramuru magmatism to the group of post-collisional bodies, equigranular high potassium calc-alkaline granites of the NE of Rio Piranhas-Seridó Domain.
Resumo:
This research aims to study wall paitings created by artists Newton Navarro and Dorian Gray, installed in public buildings of modern architecture, in Natal/RN from 1950 to 1970. The subject is seen by focusing on its concepts and characterization, linked to the ideia of integration of the arts and the meaning of modern mural painting in Brasil. The study presents an analyses of those paitings considering themes, techiniques and dimensions, comparing the solutions of local artists with brasilian muralist painters, particularly the work of Cândido Portinari. Registers of artistic works show a view of the inclusion of arts in modern architecture in the city
