Navegando por Assunto "Gravimetria"

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Acesso aberto (Open Access)
Aplicação do gravímetro de poço em problemas de avaliação de formação no Brasil
(Universidade Federal do Pará, 1992-02-27) GONÇALVES, Carlos Augusto; EVANS, Hilton Bernard
The first borehole gravity survey in Brazil was carried out during October and November of 1990 in Sergipe-Alagoas basin through a joint program between the Federal University of Pará, PETROBRAS and United States Geological Survey. The principal purpose of the survey was to test the applicability of this tool in Brazilian sedimentary basins. Another purpose was to compare the borehole gravimeter (BHGM) data with existing open-hole density log (CDL). The survey was conducted in three wells in Carmópolis field and the data were transformed to miligals, corrected for tide, drift and terrain effects and preliminary density values calculated. The region in which the surveys were carried out consists of an evaporite sequence overlying basement rock ocurring relatively near the surface. The large contrast between these units and the rest of sedimentary section results in vertical gravity anomalies. It is necessary to correct the BHGM density data for these anomalies. The resulting BHGM density data were then compared to that obtained from the CDL. Furthermore, lithology parameters defined from well log data were used to calculate porosities from both the BHGM and CDL density data, showing possible new oil intervals that can be tested.
Acesso aberto (Open Access)
Estudo gravimétrico de resíduos dos grandes geradores supermercadista; atacadista, hotelaria e restaurantes na região metropolitana de Belém - PA
(Universidade Federal do Pará, 2023-02-27) FRANÇA NETO, Raymundo da Costa; NORAT, Maria de Valdivia Costa; http://lattes.cnpq.br/1628995172582591
This study addresses physical characteristics of gravimetry, presenting as a context the characteristic condition of waste for better use of recyclable waste for recycling, with organic solid waste digestible through technologies that can be better used. The main objective of the study is to identify, through gravimetric data, the possible technical relevance for the waste generated by large generators in the metropolitan region of Belém, for a better use of waste. In this way, it will have a contribution to increase the useful life of the sanitary landfill located in the area under study. The importance of gravimetric data for the survival of sanitary landfills is because it is an important tool in terms of the Solid Waste Management Plan, allowing the analysis of quantitative and qualitative data from the gravimetry of large generators, allowing to present the difficulties and possibilities to implement a disposal system with better use of waste and to identify which are the major generators of solid waste in the current situation in the Metropolitan Region of Belém. The development of this research was divided by primary and secondary data; data analysis for the purpose of results regarding the study of gravimetry, descriptive statistics were analyzed; gravimetric analysis by graph; analysis of the gravimetric composition of RS through boxplot graphs; KruskallWallis test – GG; and literary study for foundation. The results of the survey show that the amount of digestible organic matter, as the highest power in the waste, is around 80.9%, confirming that the organic waste from large generators is completely avoidable for disposal in landfills, and should be directed to treatments with technology sustainable production of energy or compounds, leading to relevant reflections on waste to propose composting techniques, generating waste inputs for agriculture.
Acesso aberto (Open Access)
Estudos hidrogeoquímicos e geofísicos na região da Braquidobra de Monte Alegre-PA
(Universidade Federal do Pará, 2005-04-11) LOPES, Elem Cristina dos Santos; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
The Monte Alegre brachyanticline is located in the central-western Pará and is one of the most striking structures of the Paleozoic Amazon sedimentary basin. The dome outcropping surface is elliptical with axes of 30 and 20 km trending NESW and NW-SE, respectively. At the present erosion level, rocks of the Ererê, Barreirinha, Curiri, Oriximiná, Faro, Monte Alegre, Itaituba and Alter do Chão formations, as well as the Penatecaua diabase are exposed. Thermal springs with temperatures from 29 to 37ºC issue out of the Ererê Formation. The present study focuses on the physico-chemical characterization of surface and groundwater that occur within the dome and on the interaction with their mineral environment. In addition, the thermal waters are also characterized isotopically and their subsurface temperatures estimated with basis on the silica and Na-Ca-K geothermometers. Gravimetric and resistivity methods were applied aiming at detecting potential sources that could account for the heating of the thermal waters. The Piper diagrams show a wide chemical variation for both the surface and groundwater which spread over the bicarbonate, calc-sulfate and sodic-chloride fields. The thermal waters are chemically more homogeneous and fall on the bicarbonate and sodic-chloride fields. This variability reflects the composition of the rocks through which the waters migrate, whose components result mainly from hydrolysis and redox reactions involving pyrite and sulfate minerals. Most water samples are in equilibrium with kaolinite as deduced from activity diagrams constructed at 25ºC, 1 atm and at quartz saturation. The thermal water samples cluster near the boundary kaolinite-sericite, whereas a few samples of surface waters that drain the Itaituba Formation plot near the line separating the kaolinite and leonhardite stability fields. The samples of the Menino Deus thermal spring collected in October/2002 reached equilibrium with sericite but failed to equilibrate with paragonite despite their Na/K ratios being higher than unity. Furthermore, most water samples are saturated with quartz. During the dry season, sample FT-27 and those from the Menino Deus thermal spring presented higher silica contents causing them to equilibrate with pyrophyllite. Isotopic data show that the Monte Alegre thermal waters have a meteoric origin with δ18O and δD values coincident with the global meteoric water line, although slightly enriched in deuterium. The excess of deuterium varies seasonally, being recorded values of 11,8-14,8 ‰ in the dry season and 4-9,5 ‰ in the wet season. Sub-surface temperatures for the thermal waters estimated with the silica geothermometer yield mean values of 71°C (wet season) and 83°C (dry season). Average water circulation depths ranging from 1560 m (wet season) to 1900 m (dry season) were calculated assuming a geothermal gradient of 30°/km and using the estimated sub-surface temperatures. After infiltrating into the ground, these meteoric waters are heated and rise back to the surface through a channel way network, particularly NE-SW and N-S-trending faults which truncate the brachyanticline flanks. Gravimetric surveys allowed to infer the presence of a lacolith-like body at a depth of about 1.3 km. This body is thicker close to the central portion of the brachyanticline. Contact relationships between sedimentary units and the laccolith could also be defined. Likewise, fractures and faults could be mapped at depth whose traces are visible on SRTM radar images. Resistivity profiles did not identify any thermal anomaly in the area, but they confirm the lithological diversity of the geological units as well as faults that may have served as conduits to the fluids.
Acesso aberto (Open Access)
Modelos de evolução e colocação dos grantitos paleoproterozóicos da Suíte Jamon, SE do Cráton Amazônico
(Universidade Federal do Pará, 2006-10-27) OLIVEIRA, Davis Carvalho de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The 1.88 Ga, anorogenic, A-type Jamon suite and associated dikes intruded 2.97 – 2.86 Ga-old Archean granitoids of the Rio Maria Granite-Greenstone Terrane which lies to the south of Serra dos Carajás, in the southeastern domain of the Amazon Craton, northern Brazil. Petrographic and geochemical aspects associated with magnetic susceptibility and gamma-ray spectrometry data showed that the Redenção and the northern part of Bannach plutons are normally zoned, with mingling relationships that indicate multiple magma injections in their construction. Both were formed by two magmatic pulses: (1) a first magma pulse which fractionated in situ after shallow crustal emplacement and generated a series of coarse, evengrained monzogranites with variable modal proportions of biotite and hornblende; (2) a second, slightly younger magma pulse, localised in the center of both plutons, and composed of a more evolved liquid from which even-grained leucogranites were derived. Seriated and porphyritic biotite monzogranite facies intruded the coarse (hornblende)-biotite monzogranites and formed anellar structures within the Redenção pluton. The magmatic zoning is marked by a systematic decrease in mafic mineral modal content, plagioclase/potassium feldspar and amphibole/biotite ratios, and anorthite content of plagioclase. TiO2, MgO, FeOt, CaO, P2O5, Ba, Sr, and Zr decreased, and SiO2, K2O, and Rb increased in the same fashion. Magmatic differentiation was controlled by fractionation of early crystallized phases, including amphibole±clinopyroxene, andesine to calcic oligoclase, ilmenite, magnetite, apatite, and zircon. The Jamon suite is subalkaline, metaluminous to mildly peraluminous, ferroan alkali-calcic, and displays geochemical affinities with within-plate A-type granites. The ubiquitous occurrence of magnetite and titanite as well as high magnetic susceptibility values demonstrate that granites of the Jamon suite are oxidized in character. Oxidized A-type granites have high FeOt/(FeOt+MgO), TiO2/MgO, and K2O/Na2O ratios and low CaO and Al2O3 compared to calc-alkaline granites. The oxidized character of the Jamon suite makes it more akin to the USA Mesoproterozoic magnetiteseries A-Ttype granites but differs from the reduced rapakivi granites of the Fennoscandian Shield, and Serra dos Carajás and Velho Guilherme suites of the Carajás province, probably because of different magmatic sources. The Jamon suite probably crystallized near or slightly above the nickel-nickel oxide (NNO) buffer and an Archean sanukitoid biotite-hornblende quartz diorite source was proposed for the oxidized Jamon magmas. Gravity modelling indicates that the Redenção and Bannach plutons are sheeted-like composite laccolithic intrusions, ~6 km and ~2 km thick, respectively. These plutons follow the general power law for laccolith dimensions and are similar in this respect to classical rapakivi granite plutons. Gravity data suggest that the growth of the northern part of the Bannach pluton was the result of the amalgamation of smaller sheeted-like plutons which successively intruded in sequence from northwest to southeast. Jamon suite plutons were emplaced in an extensional tectonic setting with the principal stress oriented approximately along NNE-SSW to ENE-WSW, as indicated by the occurrence of diabase and granite porphyry dike swarms, orientated WNWESE to NNW-SSE and coeval with the Jamon suite. The 1.88 Ga A-type granite plutons and stocks of Carajás are disposed along a belt defined by the general trend of the dike swarms. The inferred tabular geometry of the studied plutons can be explained by magma transport via dikes and it is supported the high contrast of viscosity between the granites and their Archean country rocks. Mechanisms responsible for emplacement of granitic plutons, and in particular of anorogenic A-type plutons, are still debated. A magnetic fabric study derived from anisotropy of magnetic susceptibility (AMS) measurements was applied to the Redenção pluton in order to understand its emplacement history. High magnetic susceptibilities (K from 1 x 10-3 SI to 54 x 10- 3 SI) indicated that magnetic fabrics are primarily carried by ferromagnetic minerals (magnetite). Low P' values and absence of intracrystalline deformation features indicated that the magnetic fabric is of magmatic origin. The magnetic fabric is well organized and characterized by concentric steep foliations associated with moderately to gently plunging lineations. The lack of a well-defined unidirectional linear fabric at pluton scale suggests the reduced or null influence of regional stresses during granite emplacement. Three stages are proposed for construction of the Redenção pluton, which reconcile the tabular shape of the intrusion with the occurrence of steep magnetic foliations: (1) ascent of magmas in vertical, northwest-striking feeder dikes and accommodation by translation along east-west-striking regional foliation planes; (2) switch from upward flow to lateral spread of magma with space for injection of successive magma pulses created by floor subsidence; and (3) in situ inflation of the magma chamber in response to the central intrusion of late facies, accompanied by evacuation of resident magmas through ring fractures.
Acesso aberto (Open Access)
Uma nova abordagem na interpretação de anomalias gravimétricas em bacias sedimentares - exemplo da Bacia do Recôncavo, Bahia, Brasil
(Universidade Federal do Pará, 1990-10-12) MENEZES, Paulo de Tarso Luiz; SILVA, João Batista Corrêa da; http://lattes.cnpq.br/1870725463184491
Acesso aberto (Open Access)
Procedimentos lineares de inversão gravimétrica para estimar o relevo 3D do embasamento de bacias sedimentares
(Universidade Federal do Pará, 2013) RAMOS, Laisse Costa; MARTINS, Cristiano Mendel; http://lattes.cnpq.br/8303640454649778
The technological improvement has provided the acquisition of a large volume of geophysical data, which is why the work of interpretation of gravity anomalies and pet relief sedimentary basins increasingly demand innovation in computational and mathematical formulation that allows for such offer. In order to obtain effective and computationally efficient solutions propose two new methods that incorporate linear inversion procedure for the solution of a nonlinear inversion problem. The first proposed method approximates the solution of the nonlinear inversion by linear inversion procedures and applies corrections in iterations from the initial approach, obeyed until the convergence criterion. The second method proposed solution approximates the nonlinear inversion of the linear inversion procedures only on the first iteration, the second iteration from the additional iterations are applied for correction. The investments made in the two new methods and nonlinear inversion, are stabilized by Tikhonov regularization functional first order (smoothness). The observations are modeled by a set of 3D vertical rectangular prisms whose thicknesses are parameters that define discreetly relief estimated at some points. The realization of nonlinear inversion procedure was necessary to validate the estimated basement relief of sedimentary basins produced by the new proposed methods, this validation is given by comparing the results obtained by the procedures of linear inversion with the inversion of nonlinear . We also evaluate the efficiency and effectiveness of the proposed methods and nonlinear inversion from synthetic tests. The proposed methods have proved more efficient than the nonlinear inversion method, since reduced computational time required to recover virtually identical reliefs. As regards efficiency, we conclude that the proposed methods are as effective as the non-linear inversion, since the estimates of the basement relief scale and are equivalent to each other in shape.
Acesso aberto (Open Access)
Transformação de estimativas suaves aplicadas à interpretação de relevos descontínuos do embasamento
(Universidade Federal do Pará, 2014-08-21) MOREIRA, Mayra Moura; SANTOS, Darcicléa Ferreira; http://lattes.cnpq.br/5813659873067927
We present a method to delineate the basement relief of sedimentary basins composed by vertical faults and horizontal plans. We assume density contrast between the basement and the sediments constant or decrease with depth, and known. The developed method determines the vertical positions for horizontal plans and horizontal positions for vertical faults through an smooth initial solution of the basement relief. We produce this smooth solution through an efficient method which delineates the smooth basement relief. The horizontal positions of two adjacent faults estimates the extension of only one horizontal terrace. Similarly, the vertical position of two adjacent horizontal terraces estimates the extension of the fault between them. The performance of the proposed method is compared with the computational time of two other inversion methods, which stabilize the solution applying the Total Variation functional. The proposed method always produced solutions in less computational time as compared with the computational time required by other methods. Tests on synthetic data contaminated with zero-mean Gaussian pseudorandom noise with a standard deviation of 0.1 mGal show which proposed method produced satisfactory results and estimated basement topographies close to simulated basement topographies. The proposed method was applied to two sets of real Bouguer anomalies: Steptoe Valley (United States) and San Jacinto Graben (United States). The method produced estimated basement topographies presenting high-angle faults in accordance with the available geological information, which the basins above mentioned were formed by extensional tectonics with the consequent formation of structural settings of sedimentary basins conditioned by normal faults.