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Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604

O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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Acesso aberto (Open Access)
Acúmulo e fracionamento de fósforo nos sedimentos do estuário do rio Coreaú (Ceará) para avaliação do impacto da carcinicultura
(Universidade Federal do Pará, 2014-11-17) AQUINO, Rafael Fernando Oliveira; KAWAKAMI, Silvia Keiko; http://lattes.cnpq.br/5306256489815710; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568
The shrimp culture (shrimp farms) is one of the activities of aquaculture widely employed in Brazilian estuaries and mangroves. The shrimps are fed with phosphate enriched compounds. Thus, the effluent produced by farms can accelerate the eutrophication process. An increase of shrimp farming has been seen in Coreaú River Estuary, state of Ceará, but data about environmental quality are scarce to allow monitoring of the region. The aim of the present research was to assess the contribution of the shrimp farms on phosphorus input to the Coreaú River Estuary. The main forms of phosphorus: bioavailable (P-Exch); bound to iron oxy-hydroxides (P-Fe), on the biogenic, autigênica carbonates and apatite (P-CFAP), on the detrital apatite (P-FAP) and organic phosphorus (P-Org) and as well as total organic carbon (%TOC) and chlorophyll-a were determined in samples of surface sediments and cores from the margins of the Coreaú River Estuary. The high concentrations of P-Total in surface sediments indicated the need for monitoring studies. The larger fraction was P-Fe, composing 30% of P-Total, approximately. These results indicate the ability of the iron oxy-hydroxides to immobilize or release phosphorus. The contribution of the farm’s effluents was evidenced by higher concentrations of P-Org in points adjacent to discharge areas. In sediment cores, the highest P-Total concentrations were found predominantly in fine sediments (silt and clay), with the P-Fe, P-CFAP and P-FAP fractions being the main contributors. The sedimentation rates and concentration increases of P-Total indicate the possible period of deforestation and starting or maximum activity of shrimp farms in the end of the 1980 and mid 1990, respectively. High phosphorus concentrations as well as %TOC and chlorophyll-a levels suggested a significant anthropogenic contribution, associated with a high potential for eutrophication.
Acesso aberto (Open Access)
Adsorção de molibdato em minerais de argila delaminados e amorfizados
(Universidade Federal do Pará, 2012-04-15) PEREIRA, Patricia Magalhães; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
The search for efficient methodologies to control environmental pollution, as well as the development of technologies in the fields chemical, physical and biological have been widely discussed in order to produce efficient alternatives to improve the quality of life and control of chemical pollutants (organic or inorganic) that over the years are being dumped into the environment so as inconsequential by households and industries. Thus, it is important to know about the adsorptive behavior of metals in the soil, because high concentrations of metals produce adverse effects on the environment. Molybdenum is an essential element for biological functions of plants and animals, but in high concentrations in the body can lead to bone deformities, anemia, abnormal liver and lead to death.The possibility of interaction of organic-inorganic compounds (Humic Acid, Urea andH2SO4) in sediments "in nature” from the region of Acre, was investigated with the aim of evaluating the possibility of applying these materials in adsorption processes in molybdate aqueous solutions. The natural samples used in this study have a high content of clay minerals, mainly smectite, kaolinite and low content of primary minerals such as feldspar and quartz. All samples "in nature" were characterized by XRD, XRF, FTIR, SEM and pHH2O and pHKCl. The modification with inorganic acid concentrations (0.25, 0.5, 1 and 1.5mol.L-1), temperature and contact time are important parameters in the process of delamination of the clay minerals. As the use of organic compounds such as urea and humic acid were efficient in the amorphization. The study by XRD in the modified samples show a change in the structure when H2SO4 at the concentrations used, but this fact is only observed for 15Å peak, characteristic of smectite, all other peaks showed no significant change. The synthesis of organic compounds promoted the amorphization of the smectite peak reference. Thus, as the sediment naturally has clay (smectite, kaolinite), confirmed by XRD and the presence of iron, indicating a transition to the montmorillonite nontronite, and with isomorphous substitution of iron is expected to strong interaction between the adsorption molybdate fractions modified with respect to the natural. The introduction of H+ due to the modification process with sulfuric acid promoted the replacement of calcium ions in the structure confirmed by semi-quantitative analysis performed by EDS. SEM analysis indicated the presence in natural samples cluster morphology, this fact was not observed in the modified samples, which was observed delamination and amorphization. The equilibrium conditions in the adsorption process were investigated in which it is inserted, time of 2 h and the solution pH was measured before and after adsorption. The equilibrium datawere represented by theisotherm models Langmuir, Freundlich and Sips. The adsorption process had better performance in the concentrations for samples and S10H15 S10UH. The humic acid modified samples contained higher Qmáx =3.43, values regression fit to the model obtained indicate Freundlich efficient adsorption process, the modified samples effective adsorbed molybdate anion in comparison to natural sample.
Acesso aberto (Open Access)
Adsorção de nitrato em rejeito de caulim organofuncionalizado com uréia
(Universidade Federal do Pará, 2012-05-30) TAVARES, Laís Conceição; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
Kaolin waste, generated in abundance by companies from Pará state, has caused to the environmental problems. In order to give input on the reuse of this waste was evaluated retention of nitrate ions on kaolin waste natural and modified with urea and studied the equilibrium of adsorption processes at solid-solution interfaces. The materials were characterized by X-ray diffraction and X-ray fluorescence (XRF and XRD, respectiely), IR spectroscopy (FTIR spectrum), scanning electron microscopy and estimated data of surface charge. Adsorption experiments of nitrate ions in the waste natural kaolin (CRJN) and modified with urea (CRJU) were performed without pH adjustment. H + concentrations were measured by direct potentiometry before and after the process of adsorption and equilibrium concentrations of nitrate were measured by ion chromatography. The results indicated: high purity kaolin waste; formation of kaolinite-urea complex confirmed by XRD reflection at 2  8,28o e d = 1.068 nm and the FTIR spectrum with the appearance of a broad band of low intensity, containing two discrete shoulder around 3500-3380 cm-1, corresponding to asymmetric and symmetric vibrations of the group-NH2 of urea-kaolinite, superimposed to the vibration of water. surface charges data, suggesting that the materials have a higher capacity to adsorb cations than anions, but depending on the concentration of H + and OH- on adsorbent, the hydroxyl surface can be protonated yielding positive charges that are reflected in the adsorption of anions, obtaining significant adsorbed nitrate, both in CRJN as CRJU (0,27-0,73 and from 0,18-0,70 3.5 mg g-1, respectively), the separation coefficient (RL) of from 0,28 to 0,828 change in free energy ΔG ° = -2,094 to + 0,445 kJ mol-1 for CRJN and ΔG° = -1,036 to + 1,32 kJ mol-1 for CRJN molecule. The data from RL indicated that the adsorption processes are less favorable in most points of the adsorption processes and based on the results of the free energy change (ΔG º) was showed low spontaneity to no spontaneity and adsorption processes are physical.
Acesso aberto (Open Access)
Adsorção simultânea de íons níquel, zinco e cobre em sedimentos argilosos da Formação Solimões no estado do Acre
(Universidade Federal do Pará, 2011-09-02) CARDOSO, Vivian Mariana Miranda; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
Torrential rains in the Amazon region provide large leaching of micronutrients, which can be controlled from the adsorption reactions of micronutrients in clay minerals. Studies on the geochemical properties of sediment containing high concentrations of clay minerals in the adsorption reactions of micronutrients is a research topic of great importance considering the proven use of clay minerals with a wide range of applications in various processes and procedures adsorption, involving the remediation of sediment, purification of air and water. In order to make contributions on the physical and chemical properties of soils and applicability of the Solimões Formation from Acre State was carried out a study to simulate natural competitive adsorption of micronutrients cobre, níquel e zinco in different adsorbents sites present in these sediment and to evaluate the influence of the attributes mineralogical, chemical and physico-chemical from these adsorption processes. Preliminary data on the mineralogy of soil samples allowed to select four stations distributed among four named as H1RA, H6B, H23A H9F and located along the BR 364 and BR 317, as well as outcrops in the river Acre. Analyses of samples were performed by XRD (using the powder in the range 2θ=o 5-75 ; analysis of clay fraction in sheets oriented air-dried in an atmosphere of ethylene glycol o and heated at 550 ° C (2θ = 3 -35 ) analysis total chemical by ICP-OES; element analysis exchangeable and available to determine parameters of soil fertility. In adsorption experiments the equilibrium concentrations of cobre, níquel and zinco were determined by AAS. We used the models of Langmuir isotherm, Sips, Toth, Temkin Rendlich-Petersen and the fit of the experimental data of adsorption. The results indicated that the samples present as major minerals quartz and clay minerals of the smectite group, mica and kaolinite mineral and the 14th (H6B) preliminarily identified as interstratified mica-chlorite smectite-mica or chlorite-vermiculite. The other minerals identified in the samples were gypsum (H1RA), microcline (H6B and H9F) and albite (H9F). The average chemical composition is represented by 60.99% SiO2, 15.91% Al2O3, 5.84% of Fe2O3, 2.21% K2O, 0.34% of Na2O, 1.26% MgO, 0.86% CaO and 0.86% TiO2. The following ranges were obtained for the parameters of fertility: pHH2O = 5.24 to 8.36; pHKCl = 3.16 to 7.02; CTCefetiva = 3.37 to 25.42 cmol c / kg;% V (base saturation) = 83.08 to 97.63; saturation% Ca = 4.28 to 69.21; saturation% = 11.32 to 76.42 Mg, K saturation% = 2.32 to 17.32;. In the adsorption experiments were obtained the following ranges for the amount of each element adsorbed (mg / g) in soil samples selected: Cu) from 91.30 to 147.46 in H1RA, 47.25 to 83.93 in H6B , 67.13 to 137.36 in H9F; 73.01 to 141.35 in H23A, Ni) from 49.97 to 93.81 in H1RA; 42.51 to 113.44 in H6B; 62.52 to 134.86 in H9F; 54.13 to 172.58 in H23A, Zn) from 50.11 to 104.50 in H1RA, 44.31 to 64.12 in H6B; 60.21 to 89.91 in H9F; 73.84-135 , 60 in H23A. In these experiments was obtained the following values for the initial pH of the aqueous suspensions of samples in H1RA pHinicial=3.88 to 5.38; in pHinicial H6B = 2.71 to 3.27; H9F in pHinicial = 3.16 to 4, 24 and in pHinicial H23A = 2.61 to 3.29. The values of pH equilibrium were 4.38 to 5.2 in the H1RA sample, 2.71 to 3.16 in H6B; 3.24 to 4.2 in H9F; 2.51 to 3.14.in H23A. It was concluded that the sediment samples analyzed have suitable properties adsorptive for simultaneous retention of Cobre, níquel and zinco in water; the samples with montmorilonite (station H23A) and mineral 14A (H6B) present adsorption of metals transition at pH values between 2.5 and 3.1. The samples H1RA H9F with different groups of clay minerals (smectite, kaolinite and mica) the adsorption of transition metals occurs at pH values between 3.2 to 5.5. The ionic strength increases with decreasing pH . The best isotherm models to describe adsorption processes of Cobre, níquel and zinco in sediment samples were the Langmuir and Sips models. The values of ns Sips indicated that the majority of adsorption systems fall between the homogeneous heterogeneous systems. The equilibrium data and thermodynamic processes of simultaneous interaction between these ions and mineral adsorbents indicated that the processes are favorable, spontaneous and the type of adsorption is specific (chemical adsorption) with the formation of inner sphere complexes.
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)
Alteração hidrotermal e potencial metalogenético do vulcanoplutonismo paleoproterozoico da região de São Félix do Xingu (PA), Província Mineral de Carajás
(Universidade Federal do Pará, 2015-08-27) CRUZ, Raquel Souza; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
The region of Sao Felix do Xingu, south-central Pará, exposes a volcano-plutonic system exceptionally well preserved and grouped in the Sobreiro and Santa Rosa formations, in which hydrothermal alteration and mineralization associated were recognized. The Sobreiro Formation consists of lava facies flow of andesitic, basaltic andesite, and dacitic composition, according to the proportions or absence of clinopyroxene and/or amphibole phenocrysts. Volcaniclastic facies is genetically associated and is represented by mafic crystals tuff, lapilli-tuff, and massive polymictic breccia. Santa Rosa Formation is fissure-contolled and composed of lava flow facies and associated volcaniclastic facies of felsic crystal tuffs, ignimbrites, lapilli-tuff, and massive polymictic breccia. Part of this system is interpreted as ash-flow caldera partially eroded and developed in several stages. Conventional petrography, X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy show hydrothermal alteration paragenesis occurring in these rocks. In general, the alteration minerals develop subeuhedral anhedral crystals and replace magmatic minerals. The types of hydrothermal alteration identified are incipient the pervasive and are distinguished propylitic, sericitic, intermediate argillic, and potassic, which overlap, and fracture-controlled silicification associated with hematite and carbonate. Propylitic alteration, prevalent in Sobreiro Formation, presents both pervasive and fracture-controlled styles. The paragenesis consists of epidote + chlorite + carbonate + quartz + sericite + clinozoisite ± albite ± hematite ± pyrite, which is overlapped by pervasive potassic alteration or fracture-controlled, mainly represented by potassic feldspar + biotite ± hematite. Locally, fracture is filling with prehnite-pumpellyite association that suggests geothermal low-grade metamorphism conditions. The sericitic alteration is marked by the occurrence of mainly sericite + quartz + carbonate ± epidote ± chlorite ± muscovite. It is manifested mainly in mafic crystal tuff. However, the overlap of these types of changes is evidenced by relics of propylitic chlorite alteration and textures of rocks, partially obliterated, in which there were only pseudomorphs of sericitized plagioclase. In the Santa Rosa Formation the sericitic alteration is pervasive and characterized by the occurrence of sericite + quartz + carbonate. Also presents fracture-controlled, which is represented by sericite + quartz. It is the main type of change identified in this unit by assigning the whitish rocks. SEM data show that, associated with the sericitic alteration occur lead phosphate, gold, rutile, and barite. The potassic alteration is more subordinate, generally associated with granitic porphyry and locally to rhyolites. Paragenesis is given by microcline + biotite + chlorite + carbonate + sericite ± albite ± magnetite. The intermediate argillic alteration was recognized in rhyolites and possibly corresponds to the final stages of hydrothermal alteration. It is characterized by the presence of montmorillonite + illite + chlorite + sericite ± kaolinite ± halloysite ± quartz ± hematite, which were identified by infrared spectroscopy and XRD. It gives whitish to whitish pink to the rocks. The hydrothermal alteration types were mainly controlled by temperature, fluid composition, and fluid/rock ratios. They are compatible with thermal anomalies related to magma, and possible temperature decrease due to mixing and neutralization with meteoric water, similar to that described in low- and intermediate-sulfidation mineralization. Gold identification and compatible accessories phases provide important information for prospective studies in the region, especially for potential intermediate- and low-sulfidation epithermal deposits of precious metals (gold and silver) in volcano-plutonic systems with related ash flow calderas, as well the Au(Cu) and Mo porphyry-type deposits.
Acesso aberto (Open Access)
Alteração supergênica dos basaltos do Porto Franco-Grajaú-MA
(Universidade Federal do Pará, 1985-10-04) VAQUERA VARGAS, Antônio; OLIVEIRA, Nilson Pinto de
Acesso aberto (Open Access)
Alterações hidrotermais associadas às rochas máfico-carbonatíticas do depósito de fosfato Serra da Capivara, região de Vila Mandi (PA), extremo sul do Cráton Amazônico.
(Universidade Federal do Pará, 2019-07-14) VIEIRA, Danilo Amaral Strauss; FERNANDES, Carlos Marcello Dias; http://lattes.cnpq.br/9442875601862372
Near the border of the states of Pará and Mato Grosso, in the Amazonian Craton, about 90 km west of the Vila Mandi district, Santana do Araguaia (PA) city, there is an unprecedented volcano–plutonism named Santana mafic-carbonatitic Complex. It is formed by a lower maficultramafic member with plutono–volcanic and other volcaniclastic lithofacies; besides an upper carbonatitic member with plutonic, effusive, and volcaniclastic lithofacies originated in a volcanic caldera environment with large areas of hydrothermal alterations and genetically related circular structures. The severe Amazon weathering partially affected this cluster, producing the Serra da Capivara Phosphate deposit supergenically. Although speculative, the Santana mafic-carbonatitic Complex is Paleoproterozoic in age, because it invades the Paleoproterozoic volcano-plutonic sequences Cinco Estrelas and Vila Mandi formations (1980–1880 Ma) and it is capped by sedimentary rocks from the same Era. The lower maficultramafic member has lithofacies with slabs of pyroxenite, and minor isolated metric blocks of ijolite and apatitite. They are medium-grained ceylonite-bearing (MgAl2O4) pyroxenites with augite (~ 90% vol.), magnesio-riebeckite, and olivine crystals replaced by clay minerals (saponite). The ijolite is composed of clinopyroxene and nepheline phenocrysts immersed in a fine-grained groundmass with nepheline, calcite, and interstitial magnetite. Apatitite blocks are composed of medium-grained apatite grains (~ 98% vol.) and calcite. The volcanic rocks of this lithofacies comprise isolated metric blocks of alkali basalt and rare associated outcrops of finegrained apatitite. This basalt rock presents plagioclase-rich groundmass and acicular augite phenocrysts as essential mineralogy. Aphyric samples have primary spherules filled with calcite and quartz, besides interstitial pyrite, iron oxides, apatite, barite, rutile, celestine, and monazite. This textural feature suggests silicate and carbonatitic melts immiscibility process. An explosive to autoclastic mafic volcaniclastic lithofacies encompasses poor sorting deposits of massive polymictic breccia, lapilli-tuff, crystal-rich tuff, and ash tuff. The autoclastic rocks reveal volcaniclastic texture comprising centimetric angular clasts sourced from autofragmentation of the mafic-plutonic plutono–volcanic lithofacies. Epiclastic sedimentary volcanogenic deposits usually cover all previous lithofacies. The upper carbonatitic member reveals coarse-grained carbonatite (sövite) lithofacies comprising reddish-yellow sövite (calcite carbonatite) composed of subhedral to euhedral calcite (85–90% vol.), with variations to magnesium-ferriferous calcite and dolomite. Primary accessories are magnetite, hematite, potassic feldspar, and pyrite. These lithotypes show hydrothermalized medium- to fine-grained carbonatite veins. Rare coarse-grained apatitite bodies occur associated with this lithofacies, which represents part of the proto-ore. An effusive carbonatite (alvikite) lithofacies reveals finegrained calcite-rich (80–85% vol.) to porphyritic alvikite, besides hematite, magnetite, potassic feldspar, and pyrite. Fragment-rich explosive carbonatitic volcaniclastic lithofacies encompassing poor sorting and texturally variable massive crystal-rich tuff, lapilli-tuff, and massive polymictic breccia formed by angular clasts sourced from host rocks and the complex. Syenitic stocks and dikes invade these rocks. The main hydrothermal magmatic alteration of the complex is represented by hydrothermalized carbonatitic rocks of reddish, brownish, and yellowish colors. The mineral paragenesis found was barite + fluorapatite + dolomite ± quartz ± rutile ± chalcopyrite ± pyrite ± monazite ± magnetite ± hematite. This alteration occurs in three distinctive ways; 1) in the deeper zones, where the minerals found were barite, fluorine apatite, and dolomite in pervasive to fracture-controlled alteration associated with deep fine carbonatites. 2) In the sövite, of weak interstitial form with mineralogy similar to the deep alterations. 3) in the alvikite with intense interstitial changes and formation of hydrothermal quartz associated with barite, fluorapatite, dolomite, monazite, celestine, and rutile. The mineral assemblage of the deeper alterations suggests initially sulphate-rich, magnesium, phosphorus, and CO2 fluids with possible transitional source between the late magmatic and the hydrothermal stages. In transition to more superficial phases of the volcanism, there was an assimilation of SiO2 from the country rocks evidenced by the formation of fine interstitial quartz crystals in alvikite. The interpreted environment of volcanic caldera occurs in the interception of regional NE-SW and NW-SE faults with up to 40 km of extension and that served as deep conduit of the precursor magma of the complex. The root of the system is represented by maficultramafic rocks and plutonic carbonatites. The pre-caldera phase involved intense degasification and hydrothermal activities as a function of magmatic evolution, and ascending by lithic faults and placing on the surface of large volume of carbonate lava (alvikites) that built the extinct volcanic building. The collapse of this structure and the topographic landslide coincided with explosive volcanism and formation of the volcanoclastic lithotypes, representing the intra-caldera filling. The late syenites may represent the post-caldera phase and sealing of these structures. The hydrothermal paragenesis identified in the Santana maficcarbonatitic Complex shows important metallogenetic potential for rare earth elements and phosphate and represents a prospective guide on Proterozoic terrains of the Amazonian Craton, like other areas of the planet.
Acesso aberto (Open Access)
Alvo Borrachudo, Serra dos Carajás (PA): rochas ígneas ricas em magnetita e apatita com mineralizações de sulfetos associada
(Universidade Federal do Pará, 1996-05-25) FARIAS, Edielma dos Santos; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
Acesso aberto (Open Access)
Ambiente geológico e mineralizações associadas ao granito Serra Dourada (extremidade meridional) Goiás
(Universidade Federal do Pará, 1983-08-29) MACAMBIRA, Moacir José Buenano; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
The Serra Dourada granite belongs to a set of domic structures, generally mineralized in cassiterite, located in the center-east of Goiás, where rocks of the Uruaçu and Brasília folding belts and the Goiás median massif dominate. In order to contribute to the petrological, metallogenetic and stratigraphic knowledge of these granitic rocks, the southern tip of Serra Dourada was selected for this study. The methodology adopted was mapping at a 1:45,000 scale, petrographic, minerographic and geochronological studies, in addition to the determination of the contents of major elements in rocks and some minerals, and of trace elements in rocks. The granitic rocks of Serra Dourada were classified as syenogranites, presenting three varieties: amphibole-biotite granite, muscovite-biotite granite and biotite granite, the latter being dominant. The K-Rb graph indicates an advanced degree of fractionation for these rocks and suggests a trend that starts from granite to amphibole and ends in muscovite. In turn, the systematic variation of the contents and ratios of some trace elements reveals an intimate relationship between these varieties, meaning multiple intrusions that correspond to different degrees of partial fusion of the original material. In attempts at dating by the Rb-SR method, it was observed that the phenomena subsequent to the initial lodging in the crust introduced possible isotopic rejuvenations. However, these granitic rocks provided maximum conventional ages close to 2 b.a. The last magmatic phases of the Serra Dourada granite were the pegmatites which, in the core of the batholith, are zoned and contain aquamarine, while at the edge they bear tantalite-columbite, emerald, muscovite and monazite. Then, large amounts of hydrothermal solutions enriched in Sn and F reached both the granite and its host, changing them to greisens. Upon contacting the enclaves, the solutions precipitated cassiterite, magnetite, fluorite and sulfides. Veins with wolframite and rutile lodged in the nearest enclaves. At lower temperatures, these solutions generated kaolin when reaching the pegmatites of the contact range. Several types of enclaves have been identified in the granite: biotitite, soda-gneiss, xenoliths of schists and quartzites, and amphibolites. The soda-gneiss enclaves are trondhjemitic in nature and also have amphibole and biotite, biotite and biotite and muscovite varieties. The similarity of the assemblage and chemistry of some mineralogical phases suggests a consanguinity between soda-gneiss and granite, with the possibility that they are partially intact fragments of the rocks that gave rise, by anatexia, to the granitic material. On the other hand, the contents and anomalous ratios of some elements of soda-gneiss indicate reaction with magma, which is emphasized by the position of these rocks in the K-Rb graph. This reaction certainly affected the isotopic ratios, allowing only to suggest an Archean age. In turn, the biotites are possibly restricted. The sequence where the Serra Dourada granite was lodged is composed of intercalations of schists and quartzites from the Serra da Mesa Group. The typical mineralizations of acid magmatism, greissens, pegmatites and granitic sills in the metasediments, in addition to xenoliths from the enclosing rocks and pronounced foliation at the edges of the body, testify to the intrusive character of the granite in these metamorphites, whose late-syntectonic event is associated with the formation of the brachyanticlinium, which agrees with the regional structural pattern. Through the mineralogical assemblage of these rocks, conditions of low amphibolite facies were attested for its formation, where pressures above 4.5 Kb and temperatures around 550°C.
Acesso aberto (Open Access)
A ametista de Pau d' Arco e Alto Bonito no Pará e a do Alto Uruguai no Rio Grande do Sul
(Universidade Federal do Pará, 1998-03-23) CASSINI, Carlos Tadeu; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Acesso aberto (Open Access)
Uma análise de cluster via CiteSpace a propósito da espectrometria WDXRF para geocientistas (2001-2021)
(Universidade Federal do Pará, 2023-08-17) CASTANHO, Rebeca Soares; PAZ, Simone Patrícia Aranha da; http://lattes.cnpq.br/5376678084716817
The present bibliometric analysis addresses the use of Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometry in geochemical analysis to evaluate scientific trends over a twenty-year period, from 2001 to 2021, using the academic and free bibliometric tool, CiteSpace. For this purpose, 941 international scientific articles involving WDXRF were collected from the Web of Science (WoS) platform using the search terms "wdxrf" or "wavelength dispersive x-ray fluorescence". The data analysis was divided into two parts: the first part aimed to understand and interpret the quantitative aspects of the scientific production related to the technique, while the second part involved a co-occurrence analysis of keywords from the retrieved works. Despite fluctuations, there has been a constant increase in the number of articles related to this spectrometry technique, with 2020 being the year with the highest productivity in the historical series (105 publications). The United States of America leads the country rankings (110 articles); however, the relatively homogeneous distribution of these studies reveals that WDXRF is a widely disseminated technique worldwide. Brazil ranks among the top ten most influential countries in this field, occupying the eighth position with 59 publications. The journal X-Ray Spectrometry, with 82 articles, stands out as the primary venue for the dissemination of research on this analytical technique. In total, 569 keywords were found, connected by 2002 co-occurrence links. The term "trace element" denotes a solidified but always relevant interest in the use of WDXRF for this level of chemical analysis. On the other hand, "nanoparticle" is the keyword with the highest citation explosion over the past two decades, particularly between 2015 and 2021, highlighting a more recent trend in the elemental characterization of nanostructured compounds. The CiteSpace program identified 13 thematic groups, with five being the most notable in the application of this instrumentation: nanomaterial characterization (cluster #0), trace-level heavy metal analysis (cluster #1), chemical speciation (cluster #2), analysis of particulate matter on filters (cluster #5), and provenance of historical ceramics (cluster #6). In summary, it can be concluded that the chemistry of geological materials does not constitute a narrowly defined body of studies concerning WDXRF. Instead, it represents a scientific frontier that expands through interdisciplinary approaches, providing new and integrated methodological approaches to geoscientific research for those who delve into this technique.
Acesso aberto (Open Access)
Análise de imagens de sensores remotos orbitais para mapeamento de ambientes costeiros tropicais e de índices de sensibilidade ambiental ao derramamento de óleo no Golfão Maranhense
(Universidade Federal do Pará, 2006-04-18) TEIXEIRA, Sheila Gatinho; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252
The oil spills in Brazil are more and frequents, causing several impacts on environments and biological communities. Envronmental sensitivy index maps of oil spils are indispensbles components of contingency and emergency answer plans for this tpe of accident. These maps present a system of classification based on geomorphologic characteristics of the áreas, which are defined by the following factors: wave and tidal energy exposure relative degree, shoreline slope and substrate type, and also, the easiness to clean and remove the oil impacted áreas. In this contect, the “Golfão Maranhense” region, located on Northern “Maranhão” State, was chosen in order to map and analyze the environmental sensitivity indexes (ESis) of oil spills on coastal environments, for in this área, we find the second largest port in draught of the world, the Porto f “Itaqui”. Moreover, this region is the route of six hundred oil tankers per year, which are potential agents that cause the oil spill. The methodological approach for creating the maps of environmental sensitivity index included the integrated analysis of coastal environments based on digital image processing from remote optical sensores, in this case, Landsat-4TM, CBERG-2 CCD and SPOT-2 HRV, SAR (Synthetic Aperture Radar) images from RADARSAT-1 Wide 1, SRTM (Shuttle Radar Topography Mission) elevation data, geographic information system and Field surveys related to geomorphology, topography and sedimentology. Using the aforementioned methods, the coastal environments recognized in “Golfão Maranhense” were grouped according to their envronmental sensitivity index: 1 – Solid men-made structures (ESI 1B); 2- Cliffs (ESI 1C); 3 – Fine grained sand beaches and móbile dunes (ESI 3ª); 4- Tidal sandflats (ESI 7); 5- Mixed intertidal Banks, tidal mudflats and ebb-tidal delta (ESI 9ª); 6- Supratidal sandflat (ESI 9C); 7- Saltmarshes (ESI 10ª); 8- Fresh marhes and intermittent lakes (ESI 10B) and 9- Mangrove (ESI 10C). This approach is efficient to recognize and analyze coastal environments and, therefore, it pernitted the sensivity index attribution for the oil spill on yhese environments, in a georefenced data base, which allows making faster e more efficiently decisions in case oil spills come to happen.
Acesso aberto (Open Access)
Análise faciológica da formação Codó (Aptiano superior) na Região de Codó (MA), leste da Bacia do Grajaú
(Universidade Federal do Pará, 2000-09-11) PAZ, Jackson Douglas Silva da; ROSSETTI, Dilce de Fátima; http://lattes.cnpq.br/0307721738107549
The Codó Formation, focused in this paper, is exposed in the adjacencies of Codó town, eastern Maranhão State, where it consists of intergraded shales, limestones and evaporites, laterally continuous, forming shoaling-upward successions averaging 2.5 m in thickness. Sedimentological features, the abundance of freshwater ostracodes and Charophyte algae, as well as the absence of any marine fauna, characterize this unit as a dominantly lacustrine unit, which can be described by three broad facies associations, attributed to: 1. central lake; 2. transitional lake; and 3, marginal lake. The central lake facies association represents the base of the shoaling upward successions and consists of two facies: a) black shale; and b) evaporite. The dominance of shale beds in this association indicates sedimentation in low energy depositional settings, typical of central lake areas, where the abundance of pyrite and the bituminous composition point to highly reducing conditions. The scarcity of infauna is indicated by the complete absence of bioturbation, which is consistent with anoxia. The evaporite facies point to a highly saline lake setting. The transitional facies association consists of: a)laminated argillite; hb)lime- mudstone; c)peloidal limestone (mudstone to packstone); and d)meso-crystalline limestone. These deposits, between central lake and marginal lake facies associations, own in the middle portion of the shoaling upward cycles, consistent with a transitional lacustrine setting. The marginal lake facies association represents the top of the shoaling upward successions and consists of a variety of intergrading lithofacies: ajmassive pelite; b)calcite-arenite; Cc) ostracodal limestone (wackestone to grainstone); d) pisoidal limestone (packstone) ; e)gipsite-arenite; £f) tuffa; and 9) rhythmite. These deposits show an abundance of sedimentary features (i.e., paleosoil, karstic surface, fenestrae) typical of subaerial and/or meteoric exposure, which is consistent with their interpretation as marginal lake deposits. A lacustrine facies model with ramp margin and low energy flow is proposed for the study area, taking into account the following characteristics: 1) low rates of sediment supply; 2) presence of areas with low relief around the lacustrine basin; 3) abundance of sedimentary features recording episodes of subaerial and/or meteoric exposure; and 4) prevalence of marginal facies. This interpretation is further suggested by: 1) the small thickness of the depositional cycles, which is attributed to decreased accommodation; 2) absence of turbiditic deposits, which are typical in lacustrine settings with pronounced slope break; and 3) absence of resedimented deposits, which are also common in bench margin lacustrine settings. The abundance of black shales and evaporites suggests a hydrologically closed lacustrine basin with stratified and saline water column for the study area. The depositonal cycles identified reveal a regressive character for this lacustrine succession. Three types of cycles were recognized: 1) complete shoaling-upward cycle; 2) incomplete shoaling-upward cycle; and 3) flooding-upward cycle. The origin of these cycles is attributed to tectonism, based on the assymetrical vertical stacking pattern. This interpretation is corroborated by the presence of sin- sedimentary deformational features related to sin- depositional sismic activity. The faciological, palaeontological and geochemical data presented in this work suggested on show that the Late Aptian marine transgression recorded in the northern portion of the São Luís-Grajaú Basin did not reach the Codó area.
Acesso aberto (Open Access)
Análise integrada da morfologia e sedimentologia do baixo curso do rio Xingu
(Universidade Federal do Pará, 2019-01-28) SILVA, Ariane Maria Marques da; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994
The Xingu River is an important tributary of the Amazon River, contributing with 5% of its total water discharge. Nevertheless, it does not contribute substantially with sediment load. The lower reaches of the Xingu River correspond to a Ria, as a result of the Holocene sea-level rise. It is also classified as a tidal river, where tides reach over 1 m at its confluence with the Amazon River. This study evaluated the morphology and sedimentology of the area, correlating it with hydrodynamics, aiming to understand the still ongoing infilling process of the Xingu Ria. The study area encompasses a stretch of about 180 km, from the Xingu-Amazon river confluence upward to the narrowing of the channel, near the city of Vitória do Xingu. During the maximum sediment discharge of the Amazon River (i.e., feb/2016) 109 bottom sediment samples were collected, whereas 11 of the sampling sites were re-sampled during the minimum water discharge period of both rivers (i.e., nov/2016). During the maximum water discharge period of the Amazon River (i.e., jun/2018), additional water level measurements were undertaken simultaneously in several locations along the Xingu River, as it was also performed during the other campaigns. The morphology was evaluated on the basis of the bathymetric surveys of the Brazilian Navy (CLSAOR/DHN), including about 20,000 points. The results showed that the infilling process of the ria lake has taken place from both ‘ends’ of the area- from the Xingu River itself, forming a prominent bay-head delta, as well as from the Xingu-Amazon River confluence, where tides have transported Amazon River sediments upstream into the Xingu Ria. Furthermore, there is a central portion of the ria lake with large cross-sectional areas, reached only by relatively small amounts of sediments, being a quiescent environment within muddy sedimentation. In a transversal perspective, sands seem to prevail along the margins, where local wave action seem to result in bluff erosion. Longitudinally, sands are substantially more frequent at the bay-head delta area, and at the confluence area, where cross-sections are clearly narrower. Results also suggest that the sediment input from the Amazon River into the Xingu ria has reduced over time, whereas the combination of cross-section area variation and the Xingu River water discharge itself reduce the sediment flux from the Amazon River into the Xingu River.
Acesso aberto (Open Access)
Análise mineralógica por difratometria de raios-X e método de análise de agrupamento (cluster analysis) como critério para individualização de horizontes bauxíticos
(Universidade Federal do Pará, 2017-03-08) OLIVEIRA, Kelly Silva; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The formation of wide profile of alteration like as bauxitic deposits on Amazon during Cenozoic period is resultant of intense intemperism caused by seasonal climate, elevated temperature and humidity that are characteristics this region. The bauxitic Province of Paragominas, localized in the east portion the state Pará and west portion of Maranhão, occupies 50,000 km2 approximately forming the largest group of bauxite of Brazil. This work was used X-ray diffractometry, a technique that requires little analysis time, minimum pretreatment steps and small sample amounts, associated with cluster analysis for identify and group samples of same horizon of bauxitic profile of the mine Miltonia 3, Paragominas-PA. The results obtain were correlated with chemical analysis, frequently used for quality control and processing of bauxites. The samples used in this work and your chemical analysis were made available for company Norsk Hydro. The mineralogical types of ore were initially defined through clusters analysis of the XRD patterns of two sections (HIJ-229 e HIJ-231) from polling mesh, with 23 holes each section, and with 375 samples analyzed in all. Based on peak position and intensity of the pattern XRD was possible discern the bauxitics horizons. Due the mineralogic similarity this horizon, the differences found in this group refer principals proportions of minerals constituents: Gibbsite, kaolinite, goethite, hematite, and, more rarely, quartz and anatase. Thought clusters analyses was possible to separate by group a set of similar samples, besides facilitate the analysis of many samples quickly and with efficient results. It was possible yet observe a good correlation of the clusters with the lithotypes identified by the company Norsk Hydro through the results of the chemical analysis. In this way, the analysis of clusters in diffractograms of samples of aluminum ore can be an efficient tool aiding in the protocols of processing of this material.
Acesso aberto (Open Access)
Análise morfoestratigráfica do estuário do Rio Marapanim - NE do Pará
(Universidade Federal do Pará, 1998-12-20) SILVA, Cléa Araújo da; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429
The estuary of Marapanim River is developed on tertiary-quaternary sediments of Barreiras and Pós-Barreiras Formation. It is inserted on "Littoral of Rias" of Pará northeast, which from High Pleistocene was submitted to marine transgression that drowned coastal paleolines and, in the maximum of Holocene Transgression, reached the coastal plateau. This portion of coast is strongly influenced by dynamic macrotides (5,3m) and salt wedge with mear salinity of 8%0 (high tide — Marudazinho) and 3%0 (low tide — Marapanim). So that, on outer funnel (Marudá) the salinity is 35°/00, representing no influente of mouth river discharge. Geomorphology of the area is subdivided in three morphologic domains: (1) Coastal Plain, constituted by strand plain, paleodune, coastal dune, salt marsh, tidal flat (sand flat and mangrove swamp), recurved spit, lake and palco tidal creek; (2) Estuarine Plain, constituted by estuarine channel (subdivided in estuarine funnel segment, sinuous meandering segment, cuspidate meandering segment and upstream channel), tidal creek and floodplain (salt marsh and fresh water marsh) and; (3) Alluvial Plain constituted by meandering channel (chute cutoff), channel deposits (channel lag deposits), overbank deposits (natural levee, crevasse-splay deposits and floodplain) and channel-fill deposits. Fourteen morphostratigraphic units was identified: floodplain, levee, chute cutoff, fresh water marsh, mudflat, channel bar, point bar, strand plain, paleodune, coastal dune, recurved spit, sand flat and salt marsh. Six stratigraphic facies are also present: point bar sand and mud, marine sands, estuarine sand and mud, estuarine muds, fluvial sands and motled sand. Stratigraphical analysis permitted recognize stratigraphic sequences: Basal Marine Transgressive (Si) with fluvial, salt marsh and shoreface environments; Marine Regressive (S2) with fluvial, fresh water marsh, tidal flat, salt marsh and strand plain environments and; Recent Marine Transgressive (S3) with estuarine (channel bar and point bar) and littoral environments (recurved spit, strand plain and coastal dune). Geological evolution of the estuary of Marapanim River is associated with sea levei oscillations that occurred during progradation and regressive cycles on Later Holocene, which in the maximum of the Holocenic Transgression eroded the highland (coastal plateau). In stillstand sea levei conditions occurred marine regressive and mud flat progradation over marine sand deposits. In present time, sand sheets are deposited over mud ilat providing partia! filling in the mouth of estuary by sand bars.
Acesso aberto (Open Access)
Análise palaeoambiental e caracterização dos Folhelhos Negros da Formação Barreirinha utilizando análises Multiproxy
(Universidade Federal do Pará, 2025-06-04) CARVALHO, Wivian Maria Rodrigues; BRITO, Ailton da Silva; http://lattes.cnpq.br/9873489431846769; HTTPS://ORCID.ORG/0000-0001-9224-5563; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
The initial sedimentation phase of the Barreirinha Formation was associated with a rapid relative sea-level rise during a significant marine transgression event that flooded the Amazon Basin. These organic-rich shales outcrop along a narrow yet extensive belt located on the southern margin of the Amazon Basin. Few studies have specifically addressed the potential paleoenvironmental variations linked to the deposition of these shales. This is mainly due to the relative lithological uniformity of these rocks—composed predominantly of fine-grained sediments—and their economic relevance, which has directed most research toward the maturation of organic matter. To investigate the paleoenvironmental variations during the deposition of these fine sediments—focusing on sedimentary dynamics, the origin, and provenance of the organic matter—a multiproxy approach was applied, combining various quantitative, semi-quantitative, and qualitative techniques. The analyzed stratigraphic succession is mainly composed of gray to black shales, exhibiting facies variations related to coarse terrigenous input and episodes of bioturbation. These features suggest a deep, distal, anoxic marine depositional environment, with no evidence of carbonate sedimentation, typical of the Abacaxis Member of the Barreirinha Formation. Mineralogical cluster analyses indicate a dominance of kaolinite, characterizing the Kaolinite Facies, with subordinate quartz, sulfates, and sulfides in the lower portions. The base of the succession includes massive fine-grained sandstones with cross-bedding, correlated with the Ereré Formation, interpreted as deltaic to inner shelf deposits. The transition to laminated shales interbedded with sandstones and siltstones marks the onset of the Devonian (Frasnian) transgression, with substantial continental input evidenced by heavy minerals, pyritized plant remains, and tasmanites. The presence of dumpstones suggests glacial influence and ice-rafted debris deposition. Upper levels show more homogeneous shales, enriched in organic matter, lacking bioturbation and detrital minerals, indicating maximum anoxia during the peak of the transgressive event in the Amazon Basin. Diagenetically, the shales underwent compaction, fracturing, mineral substitution, oxidation, and intense pyritization, mainly as framboidal pyrite—typical of reducing marine environments. The mineralogy is dominated by kaolinite and quartz, with accessory minerals indicating alteration processes and possible Jurassic-Triassic igneous intrusions (Penatecaua magmatism), which contributed to increasing the thermal maturity of the kerogen. Rock-Eval pyrolysis and biomarker analyses reveal Type II-III kerogen with gas-generating potential, ranging from immature to post-mature depending on proximity to igneous intrusions. These findings reflect a transgressive system strongly influenced by environmental controls and regional thermal input.
Acesso aberto (Open Access)
Análise tafonômica de Eremotherim laurillardi (Lund, 1842) dos depósitos pleistocenos, município de Itaituba, Pará
(Universidade Federal do Pará, 2008-08-18) FERREIRA, Denys José Xavier; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The present work deals with the taphonomic study of Eremotherium laurillardi (Lund, 1842), a ground sloth found within a Pleistocene depositional site in Itaituba town, State of Pará. The samples comprise approximately eight hundred skeletal fragments and complete pieces of this specie deposited in the Paleontological Collection of Museu Paraense Emílio Goeldi. Taphonomy is the post mortem history of fossils, the study of processes that influence preservation of potential fossils. It consists of two major aspects: biostratinomy, the study of processes affecting organism remains prior to burial and fossil diagenesis affecting potential fossils after burial. The biostratinomic study showed that the skeletal remains had a loose packing and were poorly sorted, indicating deposition in situ. Moreover, the biostratinomic study revealed that the taxonomic composition of the skeletal fragments is monotypical and monospecific related to catastrophic death (non-selective) by abrupt burial which occurred before necrolysis. Traces of abrasion and reworking during transport of the skeletal remains are insignificant and/or non-existent. Bioerosion facies have not been identified too. The non-preservation of soft parts shows that the necrolysis occurred in an aerobic environment. However, the partial presence of pyrite in the foramina and channels of ribs and teeth analyzed point to localized reducing micro environment. The skeletal remains show their morphological structures, both external and internal, well preserved suggesting that they were not exposed to the exogenous cycle, due to the quick burial. The fossildiagenetic study, conducted on samples of ribs, teeth and vertebrae, using both optical and scanning electron microscopy, revealed that both the bone and dental structures, known as Havers` channels and dentinal tubules, respectively, remained well – preserved. Additionally EDS Analysis (Energy Dispersive Spectroscopy) carried out on these components showed a nearly unaltered chemical composition relating to Ca, P, Mg, K and Na contents.
Acesso aberto (Open Access)
Análises sequenciais para o ouro em solo do salobo 3A, Serra dos Carajás
(Universidade Federal do Pará, 1989-06-07) FRANCO, Maria Esmeralda Bravo Esteves Bouça; RAMOS, José Francisco da Fonseca; http://lattes.cnpq.br/8189651755374537
The Salobo 3A area. in Serra dos Carajás in the State of Pará belongs to an elongated range. according to the WNW-E SE direction. of Archean age, which borders the northern flank of the Carajás syncline. This area has been the subject of several studies, with the aim of prospecting and extracting copper ores and using their by-products. The aim of this work is to investigate the distribution of gold in soils in the area of the Salobo 3A copper sulphide deposit. Eighteen samples were collected in horizontal and vertical profiles next to gallery G1 and another sixteen from wells PA-O8 and PA-23. Soil gold concentrations were determined according to the sequential partial opening of Gatehouse et al. (1977), which was supplemented by organic extraction. due to the low concentrations of this metal in soils. The phases considered separately were iron and manganese oxides and hydroxides (amorphous and crystalline), organic matter and clay mineral silicates and quartz. A particle size fraction < 120 mesh was chosen. to avoid the presence of larger metallic gold particles. In addition to sequential analysis. another 5 grams of the same sample were etched with HF+HCl04 and another 5 grams with HF+HCl04 followed by etching with aqua regia (Au-total). All results were compared with those obtained by the instrumental neutron activation analysis and with DOCEGEO analyzes performed through the aqua regia aperture. The main objective of this work is to show the suitability of sequential analyzes for gold in soils and, through the results obtained for the studied phases, to deepen the knowledge about the behavior of gold in a supergenic environment. Of these, it is worth noting the good correlation between the gold concentration determined in the organic matter and the Au-total concentration in the soil (or even only with aqua regia, or with values obtained by INAA). The study of the amount of organic matter related to the gold adsorbed on it seems to be in agreement with the mechanisms of mobility and transport of gold in a supergenic environment known so far. From the analyzes carried out, it is concluded that, in general, little gold is found in the native state, if the concentrations obtained by the partial extractions are compared with the Au-total concentration of the samples. This element is preferentially found in silicates (clay minerals and quartz), in organic matter and in goethite (in smaller amounts).