Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603

O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.

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Acesso aberto (Open Access)
As águas subterrâneas de Belém e adjacências: influência da Formação Pirabas e parâmetros físico-químicos para medidas de qualidade
(Universidade Federal do Pará, 1996-04-08) SAUMA FILHO, Michel; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
In the Metropolitan Region of Belém (PA) the water supply to the population comes from springs (physiographic area of Utinga) and from a network of positional tube wells, in general, in more remote urban areas or where pumping is precarious. This work evaluates the groundwater used in the Metropolitan Region of Belém, correlating data of physical, physical-chemical and chemical parameters, in an attempt to compose an understandable picture about the quality of these waters, and to verify the influence that they suffer from the geological units in which they are located. the aquifers that preserve them are located. To carry out the work, water samples were collected in two different seasonal periods: dry and rainy. After exhaustive consultation of the files of companies, institutions and researchers, 17 tubular wells were selected, 9 in Belém, 5 in Icoaraci, 2 in Mosqueiro and 1 in Ananindeua (Annex A). The most frequent turbidity indices were between 9 and 14 units (ppm of SiO2), but some wells showed higher values (33, 41 and 71 ppm of SiO2. Only in some cases, this turbidity can be immediately correlated with the silica content obtained by chemical analysis. The most frequent color measurements are in the range from zero to 7.5 U.C., with the zero index predominating. However, some wells showed a value above 100 U.C. and others, less frequent, with indices varying between 20 and 60 U.C. The pH and electrical conductivity were quite different parameters. Thus, the highest pH and electrical conductivity indices were verified in the aquifers of the Pirabas Formation. In these cases, the pH was around 6 .4 to 7.6 and conductivity between 231 and 362 µS/cm, with a discontinuity at 87.5 µS/cm, also attributed to a well associated with the aforementioned Formation. More acidic waters (pH below 6.38 and above of 4.01) are certainly attributed to the aquifers of the Barreiras and Post-Barreiras Group. The chemical constituents, notably the contents of Ca2+, Mg2+, Na+ and K+, are consistent with the interpretation of the numerical values of pH and electrical conductivity. Without exception, the concentrations of Ca2+ are higher than those of the other cations, establishing a decreasing order according to Ca2+> Mg2+> Na+>K+, with some inversion between Na+ and Mg2+. The highest concentrations of Ca2+ (soon followed by Mg2+) result from the dissolution of carbonates present in the Pirabas limestone. In fact, confirming this assertion, the concentrations of HCO-3 are also much higher than the concentrations of Cl- and SO2-4. It is to be expected, therefore, that the dissolution of Pirabas sediments produces higher concentrations of Ca2+ and HCO-3. The silica and iron contents also discriminate such waters. In general, higher silica contents correspond to greater depths, as would be expected, taking into account the action of chemical weathering on silicate minerals. As for iron, this constitutes a differentiating parameter of the waters of the Pirabas Formation, almost always at much lower levels than the corresponding values associated with the Barreiras and Post-Barreiras aquifers, with, however, exceptions, in which appreciable indices of iron related to Pirabas sediments. It should be noted that the Pirabas Formation appears in the Metropolitan Region of Belém almost always at depths greater than 100 m, although there are records of smaller depths, but these are apparently rarer situations, as is the case with well number 3. , on the University Campus, near the Guamá River, with a depth of 76 m, and the 94 m well of the Museu Paraense Emílio Goeldi, in the central area of the city (Annex A). The exhaustive consultation of the aforementioned archives of institutions, companies and researchers led to the realization that many tubular wells installed in the urban area use water associated with the Barreiras and Post-Barreiras aquifers, where the pH values are almost always, below 6 units, and electrical conductivity measurements rarely reach 100 µS/cm. Finally, it appears that there is a need for greater investments in order to increase the prospection and use of groundwater in the region, as these, in addition to dispensing with treatment prior to distribution, are still a source of resources, not dimensioned, but of great potential.
Acesso aberto (Open Access)
Aplicação da composição isotópica de multielementos no monitoramento ambiental de área circunvizinha à barragem de rejeito: o caso da mina de cobre da Serra do Sossego, Canaã dos Carajás – PA
(Universidade Federal do Pará, 2017-06-09) OLIVEIRA, Simone Pereira de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Tailings dams from ore mining activities are relevant compartment for environmental monitoring because the dam can present undesirable forms of water outlets such as infiltration. The present thesis proposed multielement isotope study in order to evaluate the use of the isotopic composition of oxygen, hydrogen, strontium and lead as a tool for the environmental monitoring of groundwater vulnerable to the tailings dam. This research was conducted in the area of the Serra of Sossego copper mine and, in addition to the isotope study, the hydrochemical characterization of groundwater and surface water was caried out. Besides, the direct reading of the isotopic composition of lead (without chemical treatment of the water sample) was applied for the first time, using multicollector inductively coupled plasma mass spectrometry, in the laboratory Para-Iso. The hydrochemical characterization of groundwater in the Serra do Sossego mine area showed that it is moderately acid (pH ~ 6). Only the AP15 and PS32 wells, under the influence of the drainage of the mixed pile (ore waste + sterile), presented high electrical conductivity (599 μS / cm2 and 694 μS / cm2) and the higher sulfate content (1.82 to 6.57 Meq/L). In general, iron (29.7 mg/L), manganese (69.7 mg/L) and copper (24.9 mg/L) present the highest metal content in the groundwter. In terms of the isotope studies, the groundwater of PS17, PS04, AP15 and PS32 wells and the water of the Dam present the least radiogenic lead isotopic composition. The water sampled in the AP15 and PS32 wells would be representative of the lead isotope signature of groundwater in the mine area (206Pb/207Pb = 1.1481 to 1.1663) and, probably, is indicative of the lead isotope composition of the meteroric water. The lead isotope composition of the groundwater of the wells PS04 (206Pb/207Pb = 1.1784-1.1850) and PS17 (206Pb/207Pb = 1.2100 to 1.2160) may indicate a small contribution of the rocks of the region (206Pb/207Pb > 1.6807). In turn, the lead isotope signature of water of the Dam (206Pb/207Pb = 1.2279) suggests, as expected, a slightly more pronounced contribution of the ore and the rocks. On the other hand, the lead isotopes of the water sampled in the wells MNA23 and PS06 show a more radiogenic signature (206Pb/207Pb = 1.6741 to 1.9196), which is similar to those of the chalcopyrite and the diabase of the Sequeirinho open pit, revealing a more significant contribution of the ore and rocks. As the lead isotope composition of water from the dam is different from that of the groundwater, it can be used for the environmental monitoring of the influence of the water from the dam in groundwater in the Serra of Sossego mine area. In those wells with less radiogenic lead isotope signature, a possible contribution of the water from the dam would result in a more radiogenic lead isotope composition in the groundwater. Conversely, in those wells with more radiogenic lead isotope signature, a contribution of the water dam for the groundwater would decrease the values of the measured lead isotope ratios. On the other hand, the application of the sulfur isotopes for environmental monitoring presented some limitation in the study area, due to the lack of contrast of the sulfur isotope composition among the sulfides of the Sossego deposit (δ 34S ~ 2-7 ‰), the water from the dam (δ 34S ~ 2 ‰), and the drainage of the mixed pile (δ 34S ~ 2‰). This prevents the recognition of a possible contribution of the tailings dam to groundwater. Mixing models using the 87Sr/86Sr ratio as a function of the strontium concentration and δ 18O values, also showed some limitations, since there is no contrast between the values of the 87Sr/86Sr ratio of the water from the dam (0. 7458 to 0.7539) and the rocks of the mine area (granite ~ 0.7474). Such similarity, in principle, would not allow identifying the contribution of the water from the dam. However, since groundwater generally exhibits less radiogenic values of the 87Sr/86Sr ratio (0.7161 to 0.7283) and well below the dam values, the strontium isotopic composition can be used for environmental monitoring of groundwater. Hydrogen and oxygen isotope data revealed that, in the rainy season, the groundwater presented values of δ 18O and δ D varying from -2.74 to -7.17‰ and from -15.6 to -46.0‰, respectively. In turn, an enrichment of 18O and D, with values of δ 18O between -1.67 and -7.29 ‰ and of δ D between -0.23 and -46.1 ‰, is observed in the dry season. Hydrogen and oxygen isotope composition of the water from the dam (δ 18O from 1.24 to 2.79 ‰ and δ D from 1.40 to 7.0 ‰) is very different from those of the groundwater and of the drainage of the pile. A mixing model performed with oxygen and hydrogen isotopes showed that these elements are the ones that best respond as indicators of the contribution of the waters from the dam to groundwater. The application of this model revealed no influence of the water from the dam on the groundwater during the period of this study. The results obtained in this multielement isotopic study suggest that the environmental monitoring of the groundwater of the Serra do Sossego mine to investigate the possible contribution of the water from the dam, can be done more efficiently with the oxygen and hydrogen isotopes. The isotopic compositions of lead and strontium can also be used for monitoring the groundwater, but this has to be done more systematically due to the small contrast between the isotopic composition of these elements in the dam water and in the groundwater. Finally, the isotopic composition of sulfur is the one that would contribute least to the environmental monitoring of the groundwater of the study area.
Acesso aberto (Open Access)
Arcabouço estrutural e geocronologia dos granitóides da região de Várzea Alegre: implicações para a evolução crustal da Província Borborema
(Universidade Federal do Pará, 2024-07-25) SOUSA, Luis Kennedy Andrade de; DOMINGOS, Fabio Henrique Garcia; http://lattes.cnpq.br/3975188208099791; https://orcid.org/0000-0002-2447-3465; GALARZA TORO, Marco Antonio; http://lattes.cnpq.br/8979250766799749; https://orcid.org/0000-0002-7271-4737
In the Borborema Province, in northeastern Brazil, several granitic batholiths and plutons are found, which are records of subduction and collision episodes related to the Brasiliano Orogeny. Within this large orogenic system, the emplacement mechanisms of many granites are closely related to the development of deep-seated shear zones, one of which is the Patos Shear Zone, which in its western segment is composed of slices of rocks such as granites, gneisses, metapelites, quartzites, and amphibolites that form an imbricated system. In this context, the present work was carried out with the aim of bringing new geochronological and microstructural data to add to the understanding of the nature of the processes that formed and modified the undifferentiated granitoids in the Várzea Alegre region (CE). The granites are classified as Biotite Monzogranite and Garnet Monzogranite, they present phaneritic and porphyritic textures, in some places, their mineralogical composition is mainly composed of plagioclase, K-feldspar, and quartz, in addition to biotite, muscovite, and garnet. The granitoids are composed of elongated bodies concordant with the host rocks. The deformation imposed on the granitic bodies developed ductile structures with NE-SW orientation and kinematic criteria indicate that the deformation occurred predominantly dextral. Microstructural features, observed mainly in rocks near the edges of the granitic bodies, show that quartz crystals exhibit microstructures such as sutured to lobate contacts, undulating extinction, ribbons, and the chessboard pattern, indicative of recrystallization by grain boundary migration (GBM), compatible with temperatures of 500ºC. Biotite crystals that define the mylonitic foliation characterize a spaced foliation that separates microlite domains formed by aggregates of quartz and plagioclase, with asymmetric lenticular geometry in the granites, similar to the foliation impressed on the gneisses of the Granjeiro Complex. Based on EBSD data, the granites exhibit a grain size distribution with a concentration of crystals <100 μm. From the pole figures, the quartz OPC shows that the dominant system was rhombohedral to prismatic, indicating a medium to high deformation temperature, in a context of progressive non-coaxial deformation. However, from the interpretation of the misorientation angle, it is shown that during the deformation history of the granites, these bodies underwent lower temperature deformation. U-Pb geochronological data on zircon provided crystallization ages of 573 to 576 Ma for this granitic magmatism. The Hf-TDM C model ages of these granitoids ranged from 2.84 to 3.30 Ga and the ƐHf(t) values from -21.9 to -29.6 suggesting a strong incorporation of mesoarchean crustal source. Similar Sm-Nd data in whole rock show that these granitoids have Nd-TDM model ages between 2.14 and 3.33 Ga and ƐNd(t) values between -20.02 and -31.79, suggesting a strong contribution from meso paleoarchean and paleoproterozoic crust (orosirian to riacian) to the formation of the granitic magma that originated the granites in the Várzea Alegre region (CE). These granitic bodies are classified as Itaporanga type and sin-transcurrent, as they have similar ages and structural features to other sin-transcurrent granitic bodies in the Borborema Province. These granites were generated from magmatism associated with the change in the predominant deformation in the Borborema Province, which was the result of the final stages of the Brasiliano Orogeny within the context of simple deformation, with the development of large shear zones.
Acesso aberto (Open Access)
Assinatura isotópica de Pb em sedimentos da margem leste da Baía do Guajará (orla de Belém) e rio Maguari
(Universidade Federal do Pará, 2020-10-05) BARRA, Ingledir Suely Silva; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
Estuarine sediments provide a long-term record of the accumulation of trace metals from riverside, atmospheric and anthropogenic sources. The release of trace metals from point sources is largely controlled by the natural processes of physical and chemical weathering of rocks, in addition to anthropogenic disturbances that can occur on a large scale. In addition to diffuse anthropogenic sources, estuarine sediments can be enriched in trace metals by antifouling paints, with high contents of metals (Cu, Zn, Pb), which are applied to ship hulls and many submerged structures to prevent the growth of fouling organisms such as bacteria, macroalgae, mussels, bivalves, and invertebrates. Pb isotopic signatures are useful tools to investigate the sources and mobility of trace metals in estuarine systems and allow to distinguish between geogenic and anthropogenic source contributions. In recent years, several isotopic Pb studies for this purpose have been conducted in the hydrographic system of Belém. The aim of this work is the application of Pb isotope geochemistry in bottom sediments, suspended particulate matter (MPS), and fragments of vessels with antifouling paint of several shipyards in Guajará Bay and the Maguari River, in the metropolitan area of Belém-PA. It is intended to verify whether the paints used in the shipyards can be considered a point source of contamination by Pb. Bottom sediment samples were collected at 9 stations along the northern and southern waterfront of Belém, at the right margin of the Guajará Bay, and 3 on the Maguari River near shipyards, 6 samples of suspended particulate matter and 4 samples of vessel hull fragments. Samples of bottom sediments at the mouth of the Una Channel (3 samples) and Paracui River (1 sample) were also collected. Finally, a sample of bottom sediments was also sampled on Barra island, in the middle of Guajará Bay, as a reference to the geogenic background. Chemical analyzes of bioavailable Pb were carried out on the bottom sediment samples by inductively coupled plasma optical emission spectrometry (ICP-OES) and Pb isotopic analyzes on all samples by inductively coupled plasma mass spectrometry with magnetic sector and multiple collectors (ICP-MS). In the bottom sediment samples from the shipyards of the Belém waterfront and the Maguari River, important variations of Pb concentrations of the bioavailable fraction occur, from a value similar to the reference point (11 mg kg-1) up to contents of 25 mg kg-1. These variations suggest incipient processes of anthropic action. Even so, the levels are within the range of concentrations found so far and do not show evidence of a significant contribution of Pb linked to the proximity of the shipyards. The similar ranges of bioavailable Pb concentration between the various sectors studied (northern and southern sectors of the waterfront Belém and Maguari River) show that there is no clear pattern of distribution of Pb levels in the sectors studied. These concentrations were shown to be systematically lower than the reference values TEL (35 mg kg-1) and PEL (91.3 mg kg-1), thus indicating that Pb is not causing harmful effects to biota in these areas of the Guajará Bay system. In the northern sector of the waterfront Belém and along the Maguari River, the variations in 206Pb/207Pb isotopic ratios are within the range of the Barra island reference point and the values considered geogenic in previous works (1.189 – 1.197). Only the point identified as “vessel graveyard” presented a lower ratio (206Pb/207Pb= 1.183) and may indicate an increase in Pb anthropogenic contribution due to the deterioration of abandoned vessels and the working shipyard. In the southern sector of the Belém shore, practically all the sediments from the shipyards and the mouth of the Una canal presented lower 206Pb/207Pb isotopic ratios (1.163 and 1.178), indicating an anthropogenic contribution. This diffuse anthropogenic contribution is apparently related to the Una channel and also to the greater concentration of shipyards and other possible sources of metals. In addition, the comparison of the Pb isotopic composition of the sediments at the mouth of the drainage channels in the northern and southern sectors of the Belém waterfront suggests the existence of a relationship between anthropogenic contribution and the size of the drainage basins, population density, and urban activities. No correlation was found between the 206Pb/207Pb isotopic ratios of the bottom sediments and corresponding MPS, however, all points fit a trend line, confirming the mixture between two different sources of Pb for both sediments and suspended material. The isotopic signatures of the hull + paint fragments are positioned along the same trend line established between a geogenic end-member and an anthropogenic end-member (aerosols), for the hydrographic system of Belém, making it impossible to identify a specific anthropogenic source of Pb from the shipyards. The comparison of these signatures of the fragments with the bottom sediments of the shipyards indicates that this possible anthropogenic source enters as one of the subordinate components of the diffuse anthropogenic contribution of Guajará Bay. Finally, based on the data from this study and the works already developed in the hydrographic system of Belém, it is proposed to extend the range of 206Pb/207Pb ratio of the geogenic Pb to 1.189 – 1.204 for the hydrographic system of Belém, as a whole.
Acesso aberto (Open Access)
Caracterização da assinatura isotópica de Pb atual e da concentração de metais pesados em sedimentos de fundo da foz do rio Guamá e da Baía do Guajará (Belém - Pará)
(Universidade Federal do Pará, 2007-11-09) NASCIMENTO, Suziane Magalhães do; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
The city of Belem launches a significant amount of domestic pollutants in natura and industrial effluents in the Guama river and the Guajara bay. Previous studies suggest that the bottom sediments deposited in the edges of the river and the bay have its chemical composition influenced by these anthropogenic inputs. The aim of this work is to characterize the Pb isotopic signature, associated to the study of the distribution of the concentration of Pb and other heavy metals (Cu, Cr and Ni) in bottom sediments from the hydrographic system of Belem (Guama river and Guajara bay), in order to evaluate the regional natural variations and to evidence possible anthropogenic contributions from the industrial and urban activities of the city of Belem. Thirty three georeferenced samples of bottom sediments from the Guama river and from the Guajara bay were collected, using a Petersen grab, with capacity to sample the first 10 cm of muddy sediments. Fourteen samples came from the left edge of the Guama river, including the Cumbu and Great islands, until it flow into the bay and nine samples from the right edge, at the city riverside. Nine samples of bottom sediments were also collected from the Guajara bay, beside eight samples from the islands (Jaguar, Jutuba, Jararaca and Mirin) and one from the riverside of Belem for the determination of heavy metal contents and Pb isotopic composition. At the laboratory, samples were dried in an oven (50°C), disaggregated in a agate mortar and sieved down to 63μm, for the separation of the fine fraction (silt + clay). The mineralogical composition of the fine fraction was determined by X-rays diffraction. The total and partial heavy metals concentrations were determined, respectively, by ICP-MS at commercial laboratory (Acme Ltda), and by ICP-OES at the Toxicological Laboratory of the Instituto Evandro Chagas, Belem. The determination of the Pb isotopic compositions was carried out on samples previously leached using HNO3 at the Para-Iso Laboratory of the Instituto de Geociencas - UFPA, and using a mixture HNO3 + HCl at the Geochronological Laboratory of the Centro de Pesquisas Geocronologicas - USP. The Pb separation and purification were carried out by ionic exchange chromatography. The Pb isotopic compositions have been determined by TIMS on a monocollector mass spectrometer VG Isomass 54E with, at the laboratory of UFPA and on a multicollector mass spectrometer VG354 at the laboratory of the USP. The results indicate that the mineralogical composition of the fine fraction of the sediments includes smectite, illite and Kaolinite. Chemical analyses of heavy metals furnished the following total and partial contents for the samples from the Guama river right edge: PbTotal (11-23 mg.Kg-1); PbPartial (9-18 mg.Kg-1); 10 CrTotal (26-69 mg.kg-1); CrPartial (11-23 mg.kg-1); NiTotal (7-29 mg.Kg-1); NiPartial (6-26 mg.Kg-1); CuTotal (7-23 mg.Kg-1); CuPartial (6-17 mg.Kg-1). For the samples from the left edge of the river, the following total and partial concentrations were obtained: PbTotal (16-20 mg.Kg-1), Pbpartial (13–19 mg.Kg-1); CrTotal (34-56 mg.kg-1), Crpartial (16-26 mg.kg-1); NiTotal (12-21 mg.Kg-1), Nipartial (12-16 mg.Kg-1), Cutotal (9-14 mg.Kg-1) and Cupartial (7-12 mg.Kg-1). The sediments from both edges of the Guama river similarly display a slight decrease of heavy metal contents downstream, in the direction of the bay. However, the sediments at south of the left edge islands display an increase of contents in the same direction. Variation in the dynamic of aquatic system of the Guama river by combined effect of currents and tides would probably account for such an opposite behavior. For the sediments from the right edge, significant variations of the metals contents were locally identified and are considered to be due to the confluence of the Aura tributary, which provokes local disturbs in the hydrodynamic of Guama river as well as a redistribution of the metals along the right edge of the river at a local scale. Physical-chemical conditions of the Aura water are probably modified by the effects of the Belem waste deposit, located on the edge of the river, by increasing of the metals solubility that may account for lower heavy metal contents of the bottom sediments from the Aura river up to the confluence with the Guama river. Consequently, the Aura river will not provide any significant input of heavy metals in the Guama river. Correlation diagrams display a good correlation between heavy metals and the organic matter and excellent correlations with Al, Mg and the Fe (r = 0.95-0.99) for the samples of the right edge of the Guama river, indicating that the heavy metals are associated to the organic matter, adsorbed by the clay-minerals (smectite, illite and Kaolinite) and, probably, associated to iron oxy-hydroxides, though they have not identified. Samples of the left edge did not provide any correlation of Pb and Cr with organic matter (r = 0.24 and 0.40), however excellent correlations were identified with Al and Fe (r = 0.94-0.97). Cu and Ni are poorly correlated with organic matter (r = 0.59 and 0.72) while the correlations with Al, Mg and Fe are good (r = 0.74-0.89). Therefore, clayminerals and, possibly, iron oxy-hydroxides prevail for heavy metals contents. The sediments of both edges of the Guama river have, respectively, total concentrations of Pb (23 and 20 mg Kg-1) and Cu (23 and 14 mg Kg-1) lower than the 35 mg Kg-1 (Pb) e 36 mg Kg-1 (Cr) values of TEL (Threshold effect level), established by the NOAA-EPA as a guide of quality of sediments and that defines the level below of which adverse biological effects will rarely occur. Then, sediments of the Guama river, even so they are in contact with domestic pollutants, do not represent any 11 risk, at the moment, for the aquatic ecosystem, at least regarding to Pb and Cu. The total concentrations of Cr (69 and 53 mg Kg-1) and Ni (26 and 18 mg kg-1), for the sediments of the right and left edges, respectively, are higher than or equal to the respective TEL values of 37 and 18 mg kg-1 for these metals and may constitute a risk for aquatic organisms of the Guama river. However, such Cr and Ni concentrations come probably from natural sources without any significant anthropic influences. The homogeneous isotopic signature of the sediments of the Guama river, together with the low Pb concentrations indicate a geogenic origin for this metal and allow to establish a value for the regional "background" of Pb concentration around 18-23 mg Kg-1. They also allow considering an isotopic signature of 1.200-1.194 for the 206Pb/207Pb ratios of Pb from natural sources, reinforcing the values previously proposed by Moura et al. (2004). The lower contents of Pb found in some samples from the right edge of the Guama river (11-13 mg Kg-1), associated to slightly anthropogenic isotopic signature (1.186 < 206Pb/207Pb < 1.193) are interpreted as a result of the influence of the Aura tributary on the sediments of the Guama river. The significant increase of Pb contents in the stream sediments of the Guajara bay is an indicator of possible future biological risks in the hydrographic system of Belem. The well established negative correlation between Pb concentrations (28-46 mg Kg-1) and 206Pb/207Pb isotopic ratios (1.172 < 206Pb/207Pb < 1.188), discards the possibility that the increase of Pb contents in the Guajara bay to be of geogenic origin and that the difference in concentration with the Guama river to be resulted only of distinct hydrodynamic processes.
Acesso aberto (Open Access)
Caracterização e origem das formações ferríferas e xistos grafitosos do Grupo Estrondo na Região de Xambioá/Araguanã-TO
(Universidade Federal do Pará, 2005) SOUSA, Wiverson do Socorro Pantoja de; KOTSCHOUBEY, Basile; http://lattes.cnpq.br/0096549701457340
In the Xambioá/Araguanã region, located in the northern Neoproterozoic Araguaia Belt, iron-formations and graphite schists of the Estrondo Group are tightly associated with amphibolites and fine to medium-grained metagabbros, which are, respectively, interbedded in and intrusive into the metasedimentary essentially siliciclastic rocks of the cited unit. In this study, these different formations are described and compared with similar rocks and lithological associations from other regions in the world. Also, the origin and the depositional environment of the iron-formations and graphite schists, as well as their relationship with the basic rocks are discussed. The iron-formations are exposed in two principal zones, up to 5 km long, that are located along the northeastern border of the Lontra dome structure and the northern border of the Xambioá structure. These zones are discontinuous and consist of lenticular bodies, 200 to 1,500m long and 50 to 800m wide. Several more discrete iron-formations were recently identified in the study area. The iron-formations display a fine and fairly regular banding and are essentially composed of variably martitized magnetite and quartz, with highly subordinate pyrite and pyrrhotite. The studied samples are, as a rule, very rich in iron (mean Fe2O3tot=83.71%; maximum Fe2O3tot=96.77%) and revealed Pb, Zn, Cu and Co contents moderately higher than those detected in Carajás, Maru, Superior-type and Algoma-type banded ironformations. A prominent positive Eu anomaly (Eu* with mean=7.57 and maximum=15.54), the REE distribution pattern displaying LREE>HREE (mean La/Yb=18.54, maximum=82.83) and high ΣREE (mean=229 ppm, maximum= 371 ppm) suggest that the Xambioá/Araguanã iron formations are derived from chemical sediments of hydrothermalexhalative origin, in main part proximal. The graphite schists are interbedded in the micaschists of the Xambioá Formation and generally make up lenticular bodies tens to hundreds of meters long. However, to the west of the Lontra structure, graphite schists crop out for several kilometers north-south. These rocks are essentially composed of muscovite, quartz and graphite. Chemically, these schists are quite similar to other carbonaceous formations described in the litterature. Only vanadium and chromium contents are somewhat higher than those normally found in comparable rocks. Carbon, the content of which have mean=5,15% and maximum=9,41%, is likely of organic origin. The amphibolites and metagabbros are mainly hosted by micaschists and graphite schists. The former are often foliated, occasionally banded or microporphyritic, while the latter are normally isotropic or incipiently foliated and, frequently, display a porphyritic texture. These rocks are composed of hornblende-actinolite and plagioclase (labradorite and localling andesine in intrusive metamafics), with subordinate quartz, biotite, magnetite and hematite. In places, scapolite phenocrysts are fairly abundant. Sulphides (pyrite, chalcopyrite, chalcocite, and covellite, sphalerite and pentlandite) occur in traces. These metabasites are tholeiitic, sub-alkaline to slightly alkaline. Their REE distribution pattern suggest that, chemically, these rocks are similar to E-MORB. The association of iron-formations, graphite schists and basic rocks likely represents a sub-marine hydrothermal setting, developed during the distensive stage of the Araguaia basin evolution. In different sectors of the eastern part of the basin, basaltic flows and cogenetic gabbroic intrusions allowed the formation of convective systems. Percolating sea-water was progressively heated and evolved to hydrothermal fluids able to remove significant amounts of iron, silica and other metals from the basic volcanics and shallow intrusives. Chemical sediments rich in iron, resulting from this exhalative hydrothermalism were deposited in restricted sub-basins, close to venting zones. Diagenesis later transformed these metalliferous sediments into iron formations. The nutrient supply by the hydrothermal fluids and appropriate physico-chemical conditions close to these zones led to the proliferation of planctons. The organic matter accumulated in these sectors resulted in carbon enrichment of the siliciclastic sediments. During the metamorphic event that marked the late stage of the Araguaia Belt evolution, abundant aqueous solutions percolated the rocks of the Estrondo Group, removing most part of the silica from the iron-formations. Iron, almost insoluble in these probably oxidizing conditions, underwent a strong relative enrichment. At that same time, the carbonaceous matter was transformed into graphite.
Acesso aberto (Open Access)
Caracterização hidrogeoquímica e isotópica (87Sr/86Sr) dos sistemas aquíferos Barreiras e Pirabas Superior nos municípios de Castanhal e Santa Maria do Pará, Estado do Pará
(Universidade Federal do Pará, 2015-09-30) SILVA, Igor Rafael Furtado da; TORO, Marco Antonio Galarza; http://lattes.cnpq.br/8979250766799749
Geological surveys and remote sensing investigations in northeastern Pará State identified features and tectonic structures that characterized the neotectonic process in this region. Hydrogeological investigations in the Metropolitan Region of Belém and its surroundings were also held with the objective of characterizing the waters of the Barreiras and Pirabas (Lower Pirabas and Upper Pirabas) systems, and to evaluate the possibility of a mix between these aquifers through faults and fractures systems and the degree of their vulnerability in relation to anthropogenic inputs. Alongside the hydrogeochemical investigations, studies using isotopic signature of strontium (87Sr/86Sr) in groundwater have been performed in order to characterize the Sr sources for each aquifer system, their geochemical histories and the potential water mixture between them. Thus, studies were carried out in the isotopic composition of strontium (87Sr/86Sr) and hydrogeochemical analyzes in subareas from Castanhal and Santa Maria do Pará, aimed at the characterization of these aquifer systems, as well as detection of any possible case mixtures occur among them. The hydrogeochemical results revealed distinct features between aquifer systems studied, highlighting the parameters pH (3.52 to 5.97 in Barreiras System; 6.17 to 6.60 in Upper Pirabas System), Electrical Conductivity (45.50 to 193.90 S/cm in Barreiras; 133.80 to 194.70 S/cm in Upper Pirabas), HCO3– (up to 32.88 mg/L Barreiras; 89.10 to 117.15 mg/L in Upper Pirabas System), Cl– (3.87 to 40.50 mg/L Barreiras; 3.33 to 6.32 mg/L in Upper Pirabas), Na+ (1.00 to 18.55 mg/L in Barreiras System; 1.35 to 2.55 mg/L Pirabas Upper System), Mg2+ (up to 1.26 mg/L Barreiras, from 2.03 to 2.81 mg/L in Upper Pirabas), Ca2+ (up to 5, 14 mg/L in Barreiras, from 21.30 to 27.38 mg/L in Upper Pirabas) and Sr2+ (0.0065 to 0.0874 mg/L in Barreiras; 0.2129 to 0.2679 mg/L in Upper Pirabas). Statistical studies have shown good correlations between the aquifers (≥ 0.7), especially during the rainy season. According to the analyzes of Piper diagrams it was found that the Barreiras aquifer has predominantly Cl–-Na+ waters, which are influenced by the contribution of meteoric water and the anthropogenic action, with pH values acids around 4.7 and high vulnerability. The waters of the Upper Pirabas Aquifer System are mostly HCO3–-Ca2+, being this hydrochemical facies strongly influenced by the dissolution of carbonate, having a pH higher than 6 and less vulnerability to human action. Isotopic results showed that the Barreiras Aquifer samples are more radiogenic (0.712716 to 0.723881) that the sample of the Upper Pirabas Aquifer System (0.706080 to 0.709063) during the dry season. During the rainy season occurred the homogenization process of isotopic ratios of aquifer systems under study. Samples of the Barreiras Aquifer System there was significant decrease in values of isotopic the 87Sr/86Sr ratios from 0.712716 to 0.723881 for a range from 0.704239 to 0.709957, getting these values similar to those found in the waters of the Upper Pirabas Aquifer System. Composition diagrams of the major ions against chloride varied greatly, possibly indicating the presence of more than two end members in these waters mixing process. The multivariate statistical analysis (PCA), together with the diagram 1/Sr vs. 87Sr/86Sr showed a trend mixture between these aquifers and the meteoric waters during the rainy season. The hydrogeochemical modeling (Schoeller diagram) indicated that the degree of mixing between of the waters of the Upper Aquifer Pirabas and Barreiras is around 10% during the rainy season. Isotopic and hydrochemical studies together with on the existing neotectonic structure in the Metropolitan Region of Belém and its surroundings suggest mixing processes between Barreiras and Upper Pirabas aquifers systems, mainly in the rainy period. The lack of a planning and management system of the use of groundwater sources in the Castanhal and Santa Maria do Pará towns, as well as throughout the Metropolitan Region of Belém, alert to the risk of contamination of the Upper Pirabas Aquifer System by anthropogenic action, which represent the best alternative for public supply of the population of Belém and its surroundings with a excellent water quality with regard to portability for human consumption.
Acesso aberto (Open Access)
Caracterização litoquímica e geocronologia Rb-Sr das rochas granitóides e ortognaisses da região de Santa Quitéria-Sobral, NW do Ceará
(Universidade Federal do Pará, 1992-12-21) TAVARES JÚNIOR, Stelio Soares.; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
In the SSW of the Sobral-Pedro II Lineament between the cities of Sobral, Forquilha and Santa Quitéria, in the northwest of the State of Ceará, there is a variety of isotropic and foliated granitic bodies, with a predominance of the former. The isotropic granites constitute batholithic masses and bodies of smaller dimensions, intrusive in the rocks of the gneissic-migmatitic complexes, in the set of supracrustal rocks, including those of the Ubajara and Jaibaras groups. The Forquilha orthogneisses, of tonalitic composition with subordinate trondhjemitic and granodiorite terms, constitute one of the individual units within the gneiss-migmatitic complexes. These rocks provided a total rock Rb-Sr age of 1981 ± 45 Ma, which is interpreted as a minimum age for gneissification processes. The similarity of this result with the ages obtained in the region of Granja evidences a significant performance of the Transamazonian Event in the NW of Ceará. The initial isotopic ratio (0.70138 ± 13) of these rocks suggests an evolution from a mantle source or from short-residence crustal protoliths. The Brasiliano granites have a predominantly monzogranitic modal composition, ranging from microclimate granites to granodiorites. They are bodies of alkaline composition, per to metaluminous, with geochemical characteristics that reveal a strong similarity with type A granites, which may represent alkaline granites of intraplate or post-tectonic tectonic environment. These characteristics, including the behavior of REEs, are also similar to those of the Mucambo and Meruoca granites. The Rb-Sr geochronological studies carried out on these granites provided an age of 524 ± 12 Ma and 482 ± 8 Ma for the Pajé and Serra da Barriga granites, respectively. As for the Morrinho Granite, conventional ages between 480 and 510 Ma were obtained. Adding these results to the existing data for the Meruoca and Mucambo granites, an epoch of intense granite genesis is evident in the entire NW region of Ceará, from the late Proterozoic to the Eo-Paleozoic. Foliated granites occur as elongated bodies in the gneissic terrains of the High Grade Belt of Cariré, in agreement with the regional structure. The geochemical characteristics obtained in these bodies show a lot of similarity with those of the isotropic granites set. However, the Rb-Sr age of 475 ± 15 Ma obtained in these granites is smaller than that of the isotropic granites and certainly corresponds to a rejuvenated age. This rejuvenation is probably related to the effects of Graben Jaibaras reactivations. It was not possible to determine the true age of the crystallization of these bodies, as well as the deformational processes that affect them, in a situation very similar to that found for the Chaval Granitoid. The arrangement of the initial ratios of the foliated granites (0.70521 ± 56) and the Pajé Granite (0.70488 ± 71) in relation to the evolution of the Rb/Sr ratios of the Forquilha orthogneisses is compatible with a derivation of the granites from these gneisses. This is not valid for Serra da Barriga Granite, which has a high initial ratio (0.70963 ± 160).
Acesso aberto (Open Access)
Contribuição à evolução geológica da parte oriental da Província Amazônia Central através da geocronologia Rb-Sr da Província Mineral de Carajás e região de São Félix do Xingu - PA
(Universidade Federal do Pará, 1992-09-21) PEREIRA, Ediléa Dutra; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
Acesso aberto (Open Access)
Datação pelo método de traços de fissão em apatita da região da estrutura dômica de Monte Alegre, Bacia do Amazonas (PA)
(Universidade Federal do Pará, 2011-04-05) NEGRÃO, Sílvia Cristina Barroso; LELARGE, Maria Lidia Vignol; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In the northern portion of the Amazonas Sedimentary Basin, south of the Monte Alegre city (PA), a semi-elliptical structure defined by a group of small hills occurs, which is known as the Monte Alegre Dome. In the central portion of the dome, Devonian rocks of the Ererê Formation crop out, while toward the edge of the structure the Neodevonian to Mesocarboniferous successions, represented by the Barreirinha, Curiri, Oriximiná, Faro and Monte Alegre formations, are exposed. Diabase dykes and sills of about 200 Ma (Penatecaua Magmatism) cut this set of rocks. The formation of this dome structure has been related to the emplacement of dykes and sills of diabase. However, the contribution of Tertiary tectonism, present throughout the Amazon Basin, cannot be ruled out for the formation of the dome, since in the eastern and southern portions of this structure the Cretaceous to Tertiary rocks of the Alter do Chão formation are in faulting contact with rocks of the Ererê formation. In this study we applied the apatite fission track thermochronology in the diabase of the Penatecaua Magmatism in order to determine the age of formation of the dome structure, and to investigate the role of the Tertiary tectonics in the development of this structure. The apatite fission track method (AFT) is applied to study the thermotectonic evolution of a region, since the quantification of the fission tracks present in the mineral permits to estimate the age at which the rock passed through a given temperature (blocking temperature), which may be related to a tectonic event (uplift / subsidence) that occurred in the area. The mafic rocks studied in the region of Monte Alegre provided ATF apparent average ages between 53.2 and 43.6 Ma. These ages are interpreted as representing major tectonic events that occurred in the Tertiary (Early to Middle Eocene) that uplifted to shallower crustal levels and the diabases and the country rocks. The thermal histories obtained after modeling the AFT data allowed the recognition of four events of cooling, which occurred at 140-110 Ma, 110-100 Ma, 55-45 Ma and 30 Ma-recent. Just one sample (TFMA-12), located outside of the dome structure, did not record the Eocene tectonic event. The ATF data modeling also permitted to estimate cooling rates ranging from 0.4ºC / Ma for slower events, up to 2.82°C / Ma for faster events. Based on these cooling rates it is suggested that 3 to 3.35 km of rocks section was removed due to the reactivation of faults at different moments during the geologic evolution of the region, mainly along the Cenozoic. The apparent ATF ages between 43.6 and 53.2 Ma, as well as the significant cooling thermal event recorded in the Eocene by the data modeling revealed the important role that the Tertiary (Eocene) tectonic in the formation of dome structure of Monte Alegre. It is believed that the apparent ages of fission tracks (43.6 and 53.2 Ma) would place limits on the age of this Tertiary tectonics.
Acesso aberto (Open Access)
Determinação da composição isotópica de chumbo e estrôncio em petróleo e derivados como ferramenta para o monitoramento ambiental
(Universidade Federal do Pará, 2010-04-13) LIMA, Cristiane Souza de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
O petróleo e seus derivados são vastamente utilizados nos dias atuais para as mais diversas atividades, entretanto, estas substâncias são também importantes fontes de poluição de compostos orgânicos nocivos aos seres vivos, e de introdução de metais pesados no meio ambiente. Dessa forma, o monitoramento de sedimentos, solos e águas naturais em áreas de processamento, armazenamento, manuseio e transporte de hidrocarbonetos deve ser constante para prevenir a contaminação ambiental decorrentes de pequenos vazamentos. Esse monitoramento é feito com a análise de substâncias orgânicas que são biodegradáveis. Alternativamente, ele pode ser realizado pela análise isotópica de metais presentes em pequenas quantidades nessas substâncias. Entretanto, a especificidade das técnicas analíticas envolvidas na extração de metais de substâncias orgânicas não incentiva o uso da composição isotópica de metais no monitoramento ambiental de hidrocarbonetos. Assim, neste trabalho aplicou-se procedimentos usuais na análise de materiais inorgânicos como rocha e solo na extração de metais em petróleo e derivados, com o objetivo de determinar a composição isotópica de chumbo e estrôncio nessas substâncias. As substâncias utilizadas nos procedimentos analíticos foram petróleo, gasolina, biodiesel, óleo lubrificante novo e óleo lubrificante usado. As duas últimas foram utilizadas para comparar eventuais mudanças na composição isotópica do chumbo e estrôncio após o seu uso em motores automotivos. Durante os procedimentos laboratoriais procurou-se encontrar as quantidades adequadas de cada tipo de amostra, para garantir a exatidão e precisão dos resultados analíticos. A implementação da metodologia de extração de metais de petróleo e derivados é o ponto central deste trabalho, onde procurou-se desenvolver um procedimento usando a infraestrutura laboratorial existente com segurança. Assim, o procedimento adotado envolveu a secura das amostras, seguida de calcinação para eliminação de matéria orgânica; dissolução da amostras com ácidos inorgânicos; separação cromatográfica do chumbo e estrôncio utilizando resina especifica de Sr (Sr.Spec); e determinação da composição isotópica de chumbo e estrôncio por espectrometria de massa. Após a realização de diversos ensaios verificou-se que as seguintes quantidades seriam adequadas para a análise isotópica de chumbo e estrôncio: petróleo (5 mL), gasolina (20 mL), biodiesel (20 mL), óleo lubrificante usado (5 mL), óleo lubrificante novo (30 mL). As composições isotópicas de chumbo e estrôncio variam dentro de um estreito limite para as substâncias estudadas. No caso do chumbo, com a razão 206Pb/207Pb apresentado os seguintes valores: petróleo (1,156), biodiesel (1,153), gasolina (1,136), óleo lubrificante novo (1,148) e o óleo lubrificante usado (1,138). Para o estrôncio a razão 87Sr/86Sr apresentou os seguintes valores: petróleo (0,70795), biodiesel (0,70896), gasolina (0,70769), óleo lubrificante novo (0,70812) e óleo lubrificante usado (0,70762). Os valores da razão 206Pb/207Pb do petróleo e derivados são semelhantes àqueles determinados na região metropolitana de Belém e atribuídos a fontes antropogências (~1,140) e, bastante distintos dos valores encontrados para fontes geogênicas (~1,192) nesta mesma região. Essas diferenças nos valores da razão 206Pb/207Pb tornam possível o uso da composição isotópica de chumbo para investigar eventual contribuição antropogênica em sedimentos e solos, proveniente do manuseio, armazenamento e transporte de petróleo e derivados. Por sua vez, a comparação da composição isotópica do estrôncio em petróleo e derivados com àquelas de água subterrâneas na região bragantina, no estado do Pará, por meio do parâmetro 87Sr(‰) mostra valores de 87Sr negativos para o petróleo e derivados, enquanto que para a água subterrânea eles são positivos. Considerando a significativa diferença apresentada nos valores de 87Sr acredita-se que a composição isotópica do estrôncio pode ser empregada como uma ferramenta alternativa para o monitoramento de águas subterrâneas em áreas onde ocorre ou ocorreu o processamento, armazenamento e o manuseio de petróleo e derivados.
Desconhecido
Determinação da razão isotópica ⁸⁷Sr/⁸⁶Sr em águas naturais e sua aplicabilidade na investigação da influência da água do mar em águas subsuperficiais de zonas costeiras na Região Bragantina-PA
(Universidade Federal do Pará, 2000-08-25) SANTOS, Adriana Bordalo Braga; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Desconhecido
Determinação das concentrações de uranio e de chumbo pelo método de diluição isotópica: aplicação em rochas da Província Mineral de Carajás.
(Universidade Federal do Pará, 2001-10-15) ESTUMANO, Gerson dos Santos; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
Desconhecido
Distribuição de metais pesados e isótopos de Pb em sedimentos de fundo do rio Murucupi-Barcarena-Pará
(Universidade Federal do Pará, 2013-08-29) OLIVEIRA, Diomar Cavalcante; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
The preoccupation with environmental contamination by trace metals by urban and industrial activities has led to studies with the purpose of measuring the impacts and incorporation of these substances on aquatic biota. This study aimed to identify by determining the levels of trace metals and Pb isotopic signatures a possible involvement of effluents coming from the urban areas and industrial wastes as sources of pollution of the Murucupi river, Barcarena region, Pará. It is intended to point out the potential of Pb isotopic signatures to detect future impacts of anthropogenic contamination with trace metals. In addition, reference values of natural metal concentrations and Pb isotopic composition were identified for this sector of the Pará river estuary system values. Eighteen samples were collected from the bottom sediment surface along rivers Murucupi (8 samples), Arrozal Channel (6 samples) and Pará river (4 samples) and two drill cores in the Murucupi river. Surface samples and sediment cores were collected with Van Veen dredge type and Russian Peat Borer, respectively. A granulometric analysis was performed with laser granulometer to quantify the percentage of sand, silt and clay. The mineralogical composition was determined by X-ray diffraction. The partial and total concentrations of the metals and Lead isotopic compositions were determined by ICP-MS. The organic matter contents were determined by volumetric redox by the Walkley Black method. Granulometric analyses showed that there was a predominance of silt over sand and clay. Mineralogical analyses performed on the total sample and in the clay fraction showed the presence of quartz, albite muscovite and clay minerals smectite, illite and kaolinite. In all three drainage study, the results indicate that the levels of Pb, Cu, Zn and Ni did not show significant differences and when exist, they may be related to natural variations in the sediment. The correlation matrices indicate that the contents of trace metals are not controlled by the organic matter and that these metals are predominantly associated with structures of clay minerals in Pará river and Arrozal Channel sediments and oxy-hydroxides of Fe and Mn in Murucupi river sediments, respectively. High correlations between the trace metals indicate that the concentrations of metals in the sediments are governed by similar chemical processes in the three drainages, excepting for Pb in the Murucupi river, which is not correlated with others metals and may have been introduced into the environment by different processes. Most of the enrichment factors, using the Pará river sediments as reference value, showed values lower than 1, indicating no evidence of anthropic influence on the trace metals concentrations. Sediments from Arrozal Channel displayed contents of trace metals slightly lower than those of Murucupi river. However, the similarity of their EF values point to natural geochemical variations. The levels of Pb, Cr, Cu, Zn and Ni were lower than TEL reference value for all the trace metals studied. Therefore the sediments of the Murucupi river and Arrozal Channel, although in contact with domestic sewage, do not represent, at the moment, no risk to aquatic organisms. The bottom sediments of Pará river exhibit a homogeneous isotopic signature (206Pb/207Pbmean = 1.204 ± 0.001), considered as geogenic, establishing a background value of 206Pb/207Pb isotopic ratio for the area. Lower values found in the Murucupi river (206Pb/207Pbmean = 1.186 ± 0.003) and Arrozal Channel (206Pb/207Pbmean = 1.193 ± 0.002) are interpreted as reflecting the influence of effluents from the urban areas (Vila dos Cabanos and Laranjal) and from Barcarena river, respectively. Through 206Pb/207Pb vs. 206Pb/204Pb and 208Pb/206Pb vs. 206Pb/207Pbdiagrams, it is possible to discard a contribution of red mud tailings as a source of pollution of the Murucupi river. The decrease in 206Pb/207Pb isotopic ratios from bottom to top in sediments of the Murucupi river corroborate the existence of a recent Pb anthropogenic contribution to the sediments in this river.
Desconhecido
Distribuição de metais pesados e isótopos de Pb em sedimentos do rio Amapari, setor de Pedra Branca do Amapari – Porto Grande, Amapá
(Universidade Federal do Pará, 2011-03-18) SILVA, Danúbia Tavares da; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
This work consists of a geochemical study of heavy metals and Pb isotopic signature of sediments from the hydrographic basin of the Amapari river, which is the main affluent of the right edge of the Araguari river, in the central region of Amapá State. The study is more precisely located in a part of the river, close to the Serra do Navio area, between the cities of Pedra Branca do Amapari and Porto Grande. The region hosts the larger mining district of Amapá, including two important gold and iron mines at the Serra do Navio. The aim of this work is to investigate the distribution of heavy metals and other metals like Al, Fe, Th and U, together with the determination of Pb isotopic composition of recent sediments that are sediments deposited at the superior edge of the river during inundation events (overbank sediments), sampled along the Amapari river and tributaries, in order to distinguish the natural contributions from the main geological units and a possible contribution of mining activities. The sampling strategy depended on two factors: (1) the occurrence of adequate outcrops and (2) the accessibility. The sediments, collected at 25 sampling points in November, 2007, include a set of samples from the Amapari river and three sets of samples collected in tributary of the right edge (Cachorrinho river and Cupixi river) and left edge (Cupixizinho river). In all the samples, granulometric, mineralogical, chemical and isotopic analyses were performed. The granulometric analyses were effectuated in order to determine the proportions of fine material (silt + clay) and clay. The mineralogical composition was determined by Xrays Diffractometry using a X-rays diffractometer with cobalt anode tube. The determination of major end trace elements contents has been carried out at a commercial laboratory (ACME Analytic Laboratory) by ICP-EOS and ICP–MS after four acids dissolution (HF + HCl + HClO4 + HNO3) in 8 whole samples and 22 samples of the fine fraction of the sediments. The elements of major interest were: Al, Fe, Pb, Mn, Cu, Zn, Ni, As, Cd, Cr, Th e U. For the isotopic analyses, the samples suffered total digestion with HF and HNO3+HCl (20 samples) and acid leaching with HNO3 (5 samples). The Pb separation and purification were achieved by ionic exchange chromatography (1x8 DOWEX resin). The Pb isotopic compositions were determined in static mode with a multi-collector thermal ionisation mass spectrometer Finnigan MAT262 at the Pará-Iso Laboratory of the IG-UFPA. The geochemical results indicate that all heavy metals behaved similarly and are enriched in the same samples, indicating that the sediments suffer the same processes of enrichment for all investigated heavy metals, excepting cadmium that displayed a different trend. No relationship between granulometry and heavy metals content was pointed out. Thus, the proportion of clays presents in the sediments does not appear to have been preponderant for heavy metals concentrations, at the contrary of that commonly occur in bottom sediments. Not significant variation of mineralogical composition has been observed between the fine fraction and the fraction superior to 62μm that account for the similarity of the chemical compositions between those fractions. In both granulometric fractions, the same main paragenesis composed by quartz, kaolinite, gibbsite and muscovite was identified. Other minerals were recognized in some of the samples (anatase, rutile, microline, etc.), which probably belong to the primary paragenesis. The presence of these minerals does not have influence on the heavy metals concentrations. The heavy metals contents furnished a better correlation with Fe than with Al contents although Fe-minerals were not been identified in the samples. The Pb isotopic compositions displayed significant variations and linear rend that permitted to construct isochrons in the 207Pb/204Pb vs. 206Pb/204Pb diagram, which defined Paleoproterozoic ages around 2,0 Ga, (Amapari river: 1964 ± 88 Ma, mswd = 1,6), indicating that the sediments came essentially from the Paleoproterozoic supracrustal units (metassedimentary and mafic rocks) and associated granitoids. Despite its extensive exposition in the area, the Archean basement does not significantly contribute as a source of the sediments. The concentrations of metals display strong variations according to the geographical location but they are randomly distributed along the Amapari river, indicating that homogenization does not occurred and that the sediments reflect the difference in the source rocks. Therefore the processes which account for that geochemical distribution are probably naturals as no was evidenced no correlation has been evidenced between metal contents and sample locations in relation the mining areas. The comparison between metals contents of the Amapari river and tributaries and those determinate by others authors in bottom sediments of a creek close to the Fe and Au mining plants of the Serra do Navio – Pedra Branca do Amapari confirms that hypothesis.
Desconhecido
Distribuição e registro histórico de metais pesados e assinaturas isotópicas de PB em testemunhos de sedimentos de fundo da Baia do Guajará, Belém-PA
(Universidade Federal do Pará, 2011-08-29) CARVALHO, Jully Hellen dos Santos; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
tuaries constitute the final destination of a significant part of dissolved and particulate materials that are brought by the rivers toward the ocean. These estuaries also act as the final destination for domestic and industrial effluent, which are most of time discarded in natura. A variety of factors and sources together with the complexity of hydrodynamics and physicochemical conditions of this kind of environment makes the study of metals pollution of estuaries a challenge. The analysis of Pb isotopes is a valuable tool to differentiate anthropogenic from geogenic sources, since the lead dispersed in the environment keeps the isotopic characteristics of the source from which it was derived, once the isotopic compositions of Pb are not affected by physical or chemical processes. The hydrographic system of Belem (PA) belongs to the Guajara estuary. In the eastern margin, is located the Belém city. The west margin is an islander set composed 39 islands. About 30 km of natural drainages divide the city, forming channels that drain into, above all, the Guajara Bay which constitutes the main water reservoir receiving pollutants produced by domestic and economic activities of the city. However, the distribution of pollutants released daily in the bay is difficult to be evaluated, due to the hydrodynamic complexity of the estuary. In this context, the purpose of this study was to combine the determination of metal concentrations with Pb isotope signature to establish a historical record and to distinguish the sources of Pb, whether natural or anthropogenic, in sediments on the west edge of Guajará Bay. Samples were collected using a Russian Peat Borer. A set of seven cores of about 50 cm length was collected and subsequently sliced from 10 to 10 cm, totalizing 31 samples. According to the speed of deposition of approximately 0.7 cm/year, previously determined for the sediments of Guajara bay with geochronology 210Pb, cores collected correspond to a historical record of approximately 70 years. The study included grain size study by centrifugation method, mineralogical identification by X-ray diffraction, geochemical analysis to determine the percentage of organic matter and heavy metal contents by ICP-MS spectrometry and isotopic mass spectrometer thermoionization (TIMS). The grain size and mineralogical study of core in bottom sediments from the west edge of the Guajará bay showed a changing of hydrodynamic regime, which became more energetic, throughout the bay over time. This statement was based on the characterization of sediments, which show predominance of silt and sand fraction with a reduction of the sand fraction with the depth and texture that ranged from sandy to sandy-silty. The mineralogical study no showed change in mineralogical composition of the clays, and kaolinite, illite and smectite are claysminerals predominant. Over time the concentrations of metals vary little, however, have detected a slight tendency to decline in more recent times, probably linked to changes in the hydrodynamic regime. Moreover, there is no evidence in the core of a significant a significant increase in metal concentrations (mean 25.3 to 29.1 mg.Kg-1) with the population increase over the last 70 years. These results indicate that the background of Pb in the bay is significantly higher than in rio Guama (18 mg.Kg-1). The isotopic composition of source 206Pb/207Pb geogenic over the cores ranged between 1.186 and 1.199. The average isotopic signature of 1.193 ± 0.0035 was established as the value of the background to the Guajará bay, this value lower than the average value of 1,196 - 1.20 previously determined for the isotope ratio 206Pb/ 207Pb of Pb geogenic in Belém region.The differences in content and isotopic composition of Pb between this study carried out by Saraiva (2007) and Nascimento (2007) on the west edge of the bay, were explained by the difference of the technique used for sampling. This difference indicated that, despite the population growth accelerated during the last decades the contribution of heavy metals by anthropic action is recent, intensifying over the last 7 years.
Desconhecido
Estratigrafia, análise de fácies e proveniência das unidades litoestratigráficas aflorantes na região de Presidente Figueiredo AM, borda norte da Bacia do Amazonas.
(Universidade Federal do Pará, 2013-11-11) NOGUEIRA NETO, Ignácio de Loiola Alvares; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
Esta dissertação apresenta os resultados de um estudo que envolve análise de fácies e de proveniência dos depósitos siliciclásticos de idades pré-cambriana e fanerozoica que constituem uma faixa continua de afloramentos na borda norte da Bacia do Amazonas. Nesse intervalo de tempo, essa borda da bacia foi caracterizada pela deposição de rochas sedimentares siliciclásticas que foram afetadas por variações climáticas extremas, como por exemplo, a Glaciação Siluriana. A Formação Prosperança (Grupo Purus, Proterozoico) e o Grupo Trombetas (Ordoviciano-Devoniano), representado pelas formações Nhamundá e Manacapuru, são as unidades litoestratigráficas que melhor registraram esses eventos paleoclimáticos na Bacia do Amazonas. A Formação Alter do Chão (Grupo Javari, Cretáceo) cobre as unidades anteriormente citadas. As fácies da Formação Prosperança estão todas relacionadas a ambientes flúvio–deltaicos e são compostas por arenitos, conglomerados e pelitos. Essas fácies foram agrupadas em três associações interpretadas como prodelta/lacustre, frente deltaica e planície braided. Quanto ao Grupo Trombetas, as fácies da Formação Nhamundá estão relacionadas a ambientes costeiros e são compostas por arenitos, pelitos e diamictitos. Essas fácies foram agrupadas de acordo com suas características em três associações e interpretadas como shoreface superior, shoreface inferior e glacial costeiro. As fácies da Formação Manacapuru estão relacionadas a ambientes costeiros e são compostas por intercalações de arenitos, pelitos e folhelhos. Essas fácies foram agrupadas em três associações representativas dos ambientes de fácies litorânea transicional, costa afora e transição shoreface–foreshore. O registro de vida nos depósitos siliciclásticos das formações Nhamundá e Manacapuru é caracterizado pela presença de traços fósseis e raros fósseis. Os traços fósseis são encontrados mais comumente nas fácies arenosas em ambas as formações. Fósseis são encontrados em folhelhos betuminosos e caracterizados por conchas de braquiópodes que sugerem a passagem de um ambiente anóxico para um ambiente com condições de manutenção da vida. Por fim, os depósitos cretáceos da Formação Alter do Chão registram uma sucessão formada por arenitos, conglomerados e pelitos. As litofácies foram agrupadas em duas associações interpretadas como depósitos de preenchimento de canal e como depósitos externos ao canal, depositadas em um sistema fluvial do tipo meandrante com variação de sinuosidade do canal e de carga mista (mixedload). Quanto aos seus constituintes minerais, a Formação Prosperança apresenta abundância de minerais estáveis, elevada maturidade composicional, com índice ZTE médio de 86,6%. Em geral, os minerais possuem forma de prismas longos, arredondados e angulosos. A Formação Nhamundá apresenta abundância de minerais estáveis, elevada maturidade composicional, com índice ZTR de 83%. Os minerais são comumente arredondados a secundariamente angulosos. A Formação Manacapuru apresenta abundância de minerais estáveis, elevada maturidade composicional e índice ZTRE de 86,4%. Os minerais são geralmente arredondados e raramente angulosos. A Formação Alter do Chão apresenta grande abundância de minerais estáveis com índice ZTRE de 96,5%. Os minerais são geralmente angulosos e raramente arredondados. Foram também realizadas análises geocronológicas pelo método U-Pb nos grãos de zircão através de LAMC-ICP-MS na Universidade de Brasília. As idades obtidas, com o auxilio dos dados de paleocorrente e assembleia de minerais pesados, indicaram as possíveis áreas-fonte. As principais áreas-fonte dos sedimentos da Formação Prosperança provavelmente são regiões localizadas ao norte/noroeste da borda norte da Bacia do Amazonas, sendo as rochas da Província Maroni-Itacaiúnas (2,2-1,95 Ga) as prováveis fontes e a idade máxima de deposição de 1,5 Ga. Para a Formação Nhamundá, os dados sugerem uma idade máxima de deposição de cerca de 0,5 Ga e indicam idades entre 0,5 e 2,8 Ga, assim como para a Formação Manacapuru. Essas idades de deposição indicam que as principais áreas-fonte são formadas por rochas de idade neoproterozoica e mesoproterozoica. Os zircões de idade neoproterozoica podem ter sido oriundos de retrabalhamento de rochas mais antigas, mas há também a possibilidade de que a fonte dos zircões neoproterozoicos e mesoproterozoicos ser a Laurásia ou até mesmo serem oriundos dos cinturões brasiliano/pan-africanos do oeste africano. Os terrenos de idade mesoproterozoica, expostos a sudoeste do Cráton Amazônico e reunidos nas províncias geocronológicas Sunsás e Rondoniana-San Ignácio, podem ter sido a fonte dos zircões neoproterozoicos. Os dados sugerem como áreas-fonte para a Formação Alter do Chão, as regiões localizadas a norte/nordeste da borda norte da Bacia do Amazonas, sendo a Província Maroni-Itacaiúnas (2,2-1,95 Ga), considerada como a principal fonte potencial para os arenitos dessa formação. Alternativamente, existe a possibilidade desses zircões provirem do retrabalhamento de formações mais antigas como, por exemplo, a Formação Prosperança.
Desconhecido
Estudo da composição isotópica de Pb em organismo bentônicos, poliquetas (Namalycastis abiuma) e oligoquetas, da Baía do Guajará e rio Guamá
(Universidade Federal do Pará, 2009-06-24) OLIVEIRA, Simone Pereira de; ROSA FILHO, José Souto de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In Guajará bay (Terminal Petroliferous do Miramar and mouth of Una Canal) and in Guamá river (mouth of Tucunduba creek), three samples of bottom sediments, three of polichaetes (Namalycastis abiuma) and five samples of oligochaetes (Tubificidae) were collected. In the biological samples lead (Pb) concentration and isotope composition were determined, whereas in the sediments samples only the Pb isotope composition was. Pb content was quantified in two representative samples of oligochaetes and polichaetes. Concentrations of 5 mg.kg-1 and 3 mg.kg-1, was obtained for these organisms, respectively. Pb concentration determined in oligochaetes was equivalent to 13% of the lead’s level of the bottom sediments of its habitat (38 mg kg-1). In spite of the Pb content of the bottom sediments of Guajará bay may suggest moderate pollution, this proportion can be considered high when it is compared with the percentual relation of 1,7% of oligochaetes and sediments of very polluted environments (p. ex. botton sediment lakes of India with lead content reaching 2.260 mg.kg-1 and oligochaetes with until 23 mg.kg-1). This result suggests that, proportionally, oligchaetes may assimilate greater amount of lead of its habitat in less polluted environments. However, the lead level in oligochaetes compared with the lead level in sediments of its habitat, showed a positive correlation, and it indicates that oligochaetes can be used as a bioindicator. The polychaetes (Namalycastis abiuma), did not show a trend that indicates any type of connection or correlation between lead level in organisms and lead level in sediments. This result indicates that polichaetes cannot be used as bioindicator of the enrichment of lead (and metals) in its habitat. Lead isotope composition of the bottom sediments in Guamá river, gave the value of 1,193 for the 206Pb/207Pb ratio which is different to the suggested a value of 1,194 for the bottom sediment of the Guamá river, and interpreted as the natural value (geogenic). This indicates a anthropogenic origin of lead in Guamá river in the sampled point (mouth of the Tucunduba creek). In Guajará bay, the sample of sediment in the mouth of the Una Canal, presented a value of 1,167 for the reason 206Pb/207Pb. In previous works, this value had been suggested as indicative of lead of anthropogenic origin. This value of 206Pb/207Pb ratio shows that the Una canal is contributing to lead level in the sediments of the Guajará bay, through of discharge of domestic effluent and solid residues. Finally, in a sediment sample collected in the Terminal Petroliferous do Miramar, also in the Guajará bay, the value of the 206Pb/207Pb ratio was 1,188. This value is lower than that suggested as natural value of the 206Pb/207Pb ratio in the bottom sediments of the Metropolitan Region of Belém, which is of 1,200. This lower value can be related to activities of the Terminal Petroliferous do Miramar. The products originated in oil have an important potential of heavy metal (including lead) dissemination to environment. In order to compare the lead isotope signature of the organisms with that of the sediments the values of the isotopic ratio 206Pb/207Pb of the organisms were divided by the respective values of thIs ratio in the sediments. If the resultant quotient, represented as R, had a value of 1± 0,004 (0,996 ≤ R ≤ 1,004), it was considered as indicative that the lead isotope signature of the organisms reflected the signature of the bottom sediments of its habitat. The values of R in 75% of the biological samples were within the interval (0,997 ≤ R ≤ 1,001). The other 25% that remain outside of this tolerance interval, correspond to the two samples of oligoquetas collected in the mouth of Una Canal. Thus, the three samples of polichaetes collected next to the Terminal Petroliferous do Miramar, and the three samples of oligoquetas collected in the Guamá river next to the mouth of Tucunduba creek show values of R within the tolerance interval. This suggest that the polichaetes (Namalycastis abiuma) and oligochaetes reflected the lead signature isotope of the environment in which they are inserted, and are good bioindicators of lead isotope composition in its habitat.
Desconhecido
Estudo da razão isotópica 87 Sr /86 em macrofosséis da Formação Pirabas, nordeste do estado do Pará
(Universidade Federal do Pará, 2001-10-10) BELÚCIO, Elcinice Ferreira; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Desconhecido
Estudo do comportamento do ouro nas formações supergênicas da área Cachoeira, nordeste do Pará
(Universidade Federal do Pará, 1993-07-20) TARBACH, Milton; KOTSCHOUBEY, Basile; http://lattes.cnpq.br/0096549701457340
In the Cachoeira area, Gurupi region, northeast of Pará, there is a volcano-sedimentary sequence composed predominantly of strongly mylonitized dacites and rhyodacites, cut by bundles of quartz veins and venules from NS to NNE-SSW direction. In this sequence, gold is present in the form of fine “free” particles, disseminated both in the veins and in the heavily carbonated host rocks, as well as associated with a sulfide paragenesis consisting of pyrite, arsenopyrite, chalcopyrite and sphalerite. Over geological time, several surfaces marked by an old phosphate laterite, an immature ferruginous laterite and a level of ferruginous sandstone, respectively, developed. Furthermore, restricted-range gossans were formed early in this supergenic framework. In this work, only the most recent lateritic cover and the gossanic bodies were studied. Laterite comprises a thick saprolithic horizon, a mottled zone and a 3-meter-thick crust composed of hematite, goethite, kaolinite and generally subordinate quartz. In this alteration mantle, both gold and silver, although “invisible”, show an enrichment in the upper part of the profile and in particular in the crust. The trace elements Zn, Mn, Ni, Co, Cr, Cu and As, in turn, show higher contents in the mottled zone or at the top of the saprolite. The gossanic bodies, which mark the zones most enriched in sulphides, are composed essentially of goethite with microcrystalline quartz, kaolinite and sericite subordinated. In addition to fragments of veins. Gold, silver and arsenic show a tendency to enrich themselves in depth. In areas with higher levels of gold, it usually appears in fine visible particles or even tiny nuggets. On the other hand, the contents of Mn, Co, Zn and Pb suffer little variation in the studied profiles, while Ni and Cr show an enrichment at the top of the latter. It is assumed that during the formation of the lateritic cover, gold and silver suffered an incipient molybization, probably in the form of chlorides and/or organic complexes, whereas in the gossanic medium these elements migrated preferentially in the form of thiosulfates. In both cases the gold and silver would have been fixed by the iron hydroxide by adsorption and/or coprecipitation. Regarding the other trace elements, it is believed that their mobilization occurred mainly in the form of sulfates and according to the physical-chemical conditions of the medium. Its redistribution and fixation in the alteration products was probably controlled by its retention by poorly crystallized iron hydroxide.

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