Navegando por Assunto "Mineralogia"

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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)
Avaliação geoquímica da ocorrência de metais pesados selecionados em sedimentais pelíticos da plataforma continental do Amazonas no trecho entre a foz do rio Pará e o cabo Orange
(Universidade Federal do Pará, 2003-04-10) LIMA, Edgar Alexandre Reis de; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
Acesso aberto (Open Access)
As bauxitas nodulares do Platô Miltônia-3, Paragominas-PA
(Universidade Federal do Pará, 2017-12-12) CALADO, Waldirney Manfredi.; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607; https://orcid.org/0000-0002-3026-5523
There are two distinct levels of bauxites on the Miltônia-3 plateau located at the Bauxite Province of Paragominas-PA. These levels are separated by a pseudopsolitic to concretionary ferruginous laterite (FL) horizon, marking a hiatus between two distinct cycles of the current bauxite profile formation. The bauxites of the upper level (2nd cycle of formation) have nodular to concrete characteristics whereas those of the basal level (1st cycle of formation) are composed by a more physically complete concrete bauxite (CB) added by another level of a more friable bauxite with clayey portions for its base (concrete bauxite with clayey bauxite - CBCB). It was noticeable the CNB located at the upper level of gibbsite-enriched horizon with low reactive silica and iron contents, which are very similar to those found on the horizon of the main bauxite ore (CB) of the profile. In field observations, on the survey fronts and in the drill holes it was found that this CNB is a gradation of the above Nodular Bauxite (NB) horizon. This gradation is observed by the increase in the size of the bauxite nodules, where their Fe-gibbsite pseudopsolites grows up by coalescence, decreasing the diffused iron and silica contents marked by the change in color from lilac-yellow to a red-orange color, to ocher, in higher depths. It is also noticeable a decrease until the complete disappearance of the Al-ferruginous pseudopsolites, in addition to the decrease of the volume of gibsytic-kaolinite clay at this level. Based on this study using macroscopic and microscopic petrography, SEM/EDS, XRD and chemical analysis, as well as Principal Component Analysis (PCA) and descriptive statistics, two evolution model proposals were developed on the genesis of the upper level of nodular bauxites of this lateritic-bauxite deposit, considering: Model (1) - Origin from the degradation of the original bauxites (1st Cycle), related to a 2nd Lateritization Cycle which consists of the preexistence of mature bauxite (CB), overlapped by FL, which was covered by "Belterra Clay". This new nodular level (NB) occurs through the coalescence process whereby the residual aluminous phase junction occurred, resulting from the migration of Fe and Si in solution out of this level and by the migration of the neighboring levels above the clayey overburden (CAP) and below that of FL and CB, forming and concentrating large scale gibbsite preferably and secondarily to kaolinite. With the continuous evolution of this level of NB, a maturation of the basal portion of this level is observed, forming the CNB whose nodules are interincreased, connecting locally, consuming neighboring levels above NB and levels below FL and CB, up to the total consumption of these; Model (2) - Its origin from a 2nd Lateritization Cycle, however from a later sedimentary deposition on the lateritic profile of the 1st Cycle. With the exposure of a source rock as a granitoid pluton (Cantão, Japiim, Jonasa, Ourém and Ney Peixoto of Neoproterozoic granites), gneiss (Archaean crystalline basement) or siliciclastic sediments (Itapecuru and Ipixuna Formations of the Upper Cretaceous), whose weathering degradation made it possible the generation of sediments of clayey nature preferentially kaolinite during the Paleogene until the beginning of the Oligocene. Migration of Fe, Si, Ca, Na, etc. occurred outside this level, preserving and concentrating the Al and O in situ, in addition to the residual Si. The process of coalescence allowed for the addition of the residual aluminous phase, preferentially concentrating the gibbsite and secondarily kaolinite, closing the first cycle of bauxite formation. Thereafter, there was a regional upwelling, followed by erosive processes that allowed for the exposure of this previously formed bauxite profile, under a seasonal climate, with an abundance of meteoric water and intense intercalated insolation, where the FL developed, of regional occurrence marking a hiatus between the formation cycles of these bauxites. New regional retraction movement, which allowed for the deposition of sediments of siliciclastic origin, which served as source rock for a new bauxite formation cycle during the Upper Miocene. They may be the same rocks from which physical and chemical degradation provided sediments for the 1st cycle of bauxite formation. Repeating the coalescence process of the residual aluminous phase, with the large scale development preferably of the gibbsite and secondarily kaolinite, closing the second cycle of NB and CNB formation.
Acesso aberto (Open Access)
Caracterização físico-química da água e mineralógica e geoquímica do material em suspensão e de sedimento de fundo do lago Amapá (Acre)
(Universidade Federal do Pará, 2006-10-27) CARVALHO, Luis Carlos Farias de; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The Amazon area is characterized by its tropical rainforest and its great fluvial and lacustrine drainage basins. In the Southwest Amazonia, there are at least three great hydrographic basins (Juruá, Purus and Madeira rivers), where the oxbow lakes are very common. The Amapá Lake is on the right margin of Acre River - one of the principal tributaries of the Purus River -, close to the capital of the State of Acre, Rio Branco, as a typical oxbow lake that it was isolated from that river. Physical-chemical parameters measurements of the waters of Amapá Lake were accomplished during dry and rainy seasons in three stations to have an idea of the implications of the seasonal variation on the observed parameters. Samples were collected for elementary chemical analysis of the waters and suspended material, besides mineralogical analyses of the suspensate. Bottom sediments were collected in three survey holes, using a Livingstone-type manual probe, in a dry season, and they were submitted to chemical, mineralogical (XRD and SEM), grain size and geochronologic analyses. The waters of Amapá Lake present high turbid, STS, ammonia, (phosphate) and chloride values that indicate antropic action. The high concentrations of Na, Mg, K, Fe, Al, Mn, Ba and Sr are related to clay minerals (smectite and illite). The sediments of Amapá Lake are silt-clayey fine, distributed in beds (clear and dark), sometimes with organic particulate matter. The mineralogy of the sediments is homogeneous along the three holes and it is mainly represented by quartz, kaolinite, illite and smectite, besides albite and Kfeldspars. The vivianite occurs as pseudomorphs after organic matter debris. They are sediments with acid pH (4-5), unlike the waters, that are alkaline, and with low values of organic matter. The sediments are mainly composed by SiO2, Al2O3 and Fe2O3, besides K2O, MgO, TiO2, CaO, Na2O, P2O5 and MnO. That composition reflects abundance of quartz and clay minerals as illite and smectite. Iron contents are probably represented by amorphous sulphides or by clay minerals (smectite). The chemical results were compared with mean of the terrestrial upper crust and Post-Archean Australian Shales (PAAS). The sediments are impoverished in Na2O, CaO, MgO, K2O and SiO2 in small proportion, and enriched in MnO, TiO2, Fe2O3 and Al2O3. The values of Al2O3, Fe2O3, MnO and TiO2 are similar to the PAAS, being the sediments of the Amapá Lake comparable to those. They are immature sediments related to the clay minerals such illite and smectite and feldspars. Among the trace elements, As and Sb are more enriched in relation to the upper terrestrial crust. They are similar to PAAS. The sediments also resemble those shales via REE's being more enriched in Eu, Gd, Tb and Dy. The suspended sediment is compatible with the Acre River suspensate in mineralogy and chemical composition, partially diverging in the grain size. The Amapá Lake was formed on Early Holocene, at 3160 years BP, presenting average sedimentation rate of 1,1 mm/yr, in colmatation stage, still receiving load in suspension from Acre River, mainly when the inundations occur. The anthropic action centered in fish farmings, deforestations, disordered human expansion, besides an earth highway around the lake, contributes to its colmatation and eutrophication.
Acesso aberto (Open Access)
Caracterização mineralógica com espectroscopia de reflectância por infravermelho (SWIR): exemplo do Complexo máficocarbonatítico Santana, sul do Cráton Amazônico
(Universidade Federal do Pará, 2021-09-21) COSTA, Jhoseph Ricardo Costa e; FERNANDES, Carlos Marcello Dias; http://lattes.cnpq.br/0614680098407362; https://orcid.org/0000-0001-5799-2694
On the border of the Pará and Mato Grosso states, in the Amazonian Craton, municipality of Santana do Araguaia (PA), there is a volcano-plutonism named Santana mafic-carbonatitic complex. This set houses the Serra da Capivara phosphate deposit. A lower mafic-ultramafic member reveals plutono-volcanic lithofacies with pyroxenite, ijolite, apatitite, and alkaline basalt. Autoclastic lithofacies contains poorly selected deposits of massive polymictic breccia, lapilli-tuff, crystal tuff, and ash tuff. Volcanogenic epiclastics rocks cover these lithofacies. The upper carbonatite member contains plutonic lithofacies with coarse calcite-carbonatite (sövite). Fine carbonatite veins with pervasive carbonatic and apatitic alterations crosscut this lithotype. Minor thick apatitite occcurs associated to this member and represents the protore of the deposit. Effusive volcanic lithofacies reveals fine calcite-carbonatite (alvikite) with porphyritic, equigranular, or aphanitic textures. A poorly sorted lithofacies of crystals tuff, lapilli-tuff, and massive polymictic breccia completes this member. Stocks and syenitic dykes invade these lithofacies. Detailed mapping suggests that the complex is a volcanic caldera in which large zones of hydrothermal alterations occur with reddish, brownish red, and yellowish carbonatitic rocks. Petrographic observations reveal paragenesis of barite + fluorapatite + calcite + dolomite ± quartz ± rutile ± chalcopyrite ± pyrite ± monazite ± magnetite ± hematite. The application of short wave infrared spectroscopy (SWIR) revealed the chemical characteristics and their importance in the crystallinity of most of these hydrothermal minerals, such as radicals (OH- and CO3), H2O molecule, and cation-OH bonds such as Al-OH, Mg-OH, and Fe-OH. The main mineral phases identified were dolomite, calcite, serpentine, chlorite, muscovite with low, medium, and high aluminum, montmorillonite (Ca and Na), illite, nontronite (Na0.3Fe2((Si,Al)4O10) (OH)2·nH2O), and epidote. The data suggest a control by temperature, fluids composition, and fluid/rock ratio during the evolution of the Santana mafic-carbonatitic complex. This low-cost exploratory technique, which is applied in hand-held samples or drill holes on a large scale, is promising in characterization of volcano-plutonic centers in regions subjected to severe weathering conditions, as well as helping to develop models for prospecting mineral deposits of Rare Earth Elements (e.g. Nd, La) associated with alkaline-carbonatitic complexes. We can even combine this tool with artificial intelligence algorithms for more robust and faster results.
Acesso aberto (Open Access)
Caracterização mineralógica de azulejos de Salvador e Belém dos séculos XVI, XVII e XIX
(2004-12) SANJAD, Thais Alessandra Bastos Caminha; ANGÉLICA, Rômulo Simões; OLIVEIRA, Mário Mendonça de; COSTA, Walmeire Alves de Melo
The present article is a study about the mineralogical composition of ancient tiles from centuries XVI, XVII and XIX, found in Belém and Salvador, in order to interpret the possible raw material and burning temperature. Quartz was identified in all samples. Other crystalline phases found are mullite, cristobalite, calcite, anorthite, hematite, gehlenite, diopside and wollastonite. Based on the probable raw material and probable burning temperature it was possible to organize the samples into three groups: group 1 - kaolinite and quartz, T between 1200º and 1728º C; group 2 - kaolinite, calcite and/or dolomite and iron oxide or hydroxide, T between 900º e 1200ºC; group 3 - quartz, clay minerals (probably kaolinite), calcite and/or dolomite, iron oxide or hydroxide, and T between 1200º e 1565º C.
Acesso aberto (Open Access)
Caracterização mineralógica e geoquímica e estudo das transformações de fase do caulim duro da região do Rio Capim, Pará
(2003-12) CARNEIRO, Bruno Santana; ANGÉLICA, Rômulo Simões; SCHELLER, Thomas; CASTRO, Elton Anderson Santos de; NEVES, Roberto de Freitas
The Capim region (Pará State, northern Brazil) is the most important kaolin district in the Amazon region, with the largest Brazilian reserves of high whiteness kaolin for the paper coating industry. The main ore (soft kaolin horizon) is located at a depth of about 20 m, being covered by a hard, iron-rich kaolin level, also called flint or semi-flint kaolin, besides a sandy-clay overburden. The beneficiation of this kaolin produces large volumes of wastes, composed mainly of coarse-grained kaolinite, deposited in basins that occupy extensive areas. The main objective of this work is to carry out mineralogical and geochemical studies of the hard kaolin, and to evaluate its thermal transformations through calcination up to 1500 oC. The results show a mineralogical composition dominated kaolinite. The evaluated thermal transformations allows us to describe a series of chemical reactions from kaolinite to metakaolinite and further development of spinel, cristobalite and mullite. For the two analyzed samples, such transformations can start at different temperatures as a result of the different chemical compositions, mainly the iron contents.
Acesso aberto (Open Access)
Caracterização mineralógica e química dos regolitos de uma área de transição savana-floresta em Roraima: uma análise da evolução da paisagem
(2012-12) MENESES, Maria Ecilene Nunes da Silva; COSTA, Marcondes Lima da
The present study was carried out in an area of transition savanna-forest of the north of Roraima state. The main objective was to characterize the landscape regoliths and evaluate the evolution of the landscape during the late Holocene and even the present-day. Thus, four topossequences representative of the geomorphological, pedological and botanical patterns along the regional landscape were selected to sampling of soils and sediments. These samples were analyzed as for their granulometrical, mineralogical, chemical and chronological characteristics. The results revealed a landscape dominated by sandy to silty soils constituted essentially of quartz and kaolinit, besides muscovite, goethite, sillimanite and albite in low amounts. The high values of SiO2 confirm the quartzic character of these regoliths. The mineralogical and chemical compositions of these materials indicate provenience of metamorphic rocks and of laterites of the area, which due to the dominant warm and humid climatic conditions during the last 1550 years before the present, has been suffering intense chemical weathering and leaching. The landscape evolution is controlled by hidrological erosion of the hillsides and the filling of the valleys of 'veredas' causing the leveling of the landscape and the development of extensive sandy plains from the interfluves soils.
Acesso aberto (Open Access)
Caracterização química e mineralógica de bauxitas da Amazônia Oriental através de métodos por fluorescência (FRX) e difração (DRX) de raios-X
(Universidade Federal do Pará, 1996-05-26) SANTOS, Antônio Carlos Figueiredo dos; SCHUCKMANN, Walter Klaus
Acesso aberto (Open Access)
The ceramic artifacts in archaeological black earth (terra preta) from lower Amazon region, Brazil: Mineralogy
(Instituto Nacional de Pesquisas da Amazônia, 2004) COSTA, Marcondes Lima da; KERN, Dirse Clara; PINTO, Alice Helena Eleotério; SOUZA, Jorge Raimundo da Trindade
Several archaeological black earth (ABE) sites occur in the Amazon region. They contain fragments of ceramic artifacts, which are very important for the archaeological purpose. In order to improve the archaeological study in the region we carried out a detailed mineralogical and chemical study of the fragments of ceramic artifacts found in the two ABE sites of Cachoeira-Porteira, in the Lower Amazon Region. Their ceramics comprise the following tempers: cauixi, cariapé, sand, sand +feldspars, crushed ceramic and so on and are composed of quartz, clay equivalent material (mainly burned kaolinite), feldspars, hematite, goethite, maghemite, phosphates, anatase, and minerals of Mn and Ba. Cauixi and cariapé, siliceous organic compounds, were found too. The mineralogical composition and the morphology of their grains indicate a saprolite (clayey material rich on quartz) derived from fine-grained felsic igneous rocks or sedimentary rocks as source material for ceramic artifacts, where silica-rich components such cauixi, cariapé and/or sand (feldspar and rock fragments) were intentionally added to them. The high content of (Al,Fe)-phosphates, amorphous to low crystalline, must be product of the contact between the clayey matrix of pottery wall and the hot aqueous solution formed during the daily cooking of animal foods (main source of phosphor). The phosphate crystallization took place during the discharge of the potteries put together with waste of organic material from animal and vegetal origin, and leaving to the formation of the ABE-soil profile.
Acesso aberto (Open Access)
Ceramic raw materials from the State of Maranhão, Brazil. Part 1: chemical and mineralogical characterization and technological properties of clays from São Luis, Rosário, Pinheiro and Mirinzal
(2012-12) MERCURY, José Manuel Rivas; CORREIA, Gricirene Sousa; VASCONCELOS, Nazaré do Socorro Lemos Silva; CABRAL JÚNIOR, Aluísio Alves; ANGÉLICA, Rômulo Simões
This work involved the characterization of clays collected in the municipalities of São Luis, Rosário, Pinheiro and Mirinzal (state of Maranhão, Brazil), based on specific mass, specific surface area, cation exchange capacity (CEC), particle size distribution, X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG-DTA) and Atterberg limits. Technological tests for ceramic applications were also carried out on compacts pressed under 20 MPa and heat-treated at 850, 950, 1050, 1150 and 1250ºC. Our results indicated that two of the clays composed of kaolinite, quartz, and anatase with high plasticity limits, have excellent properties and can be used in the whiteware industry. The other ones are red-firing clays and have a mineralogical composition of quartz, kaolin, feldspar, montmorillonite, hematite and goethite. The latter showed low and moderate values of plasticity, which makes them suitable for the production of heavy clay products.
Acesso aberto (Open Access)
Charnoquitos de Ourilândia do Norte (PA): geologia, natureza e implicações tectônicas para a Província Carajás.
(Universidade Federal do Pará, 2019-10-02) FELIX, Williamy Queiroz; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The granite-charnockite association from Carajás Province is spatially associated with gabbronorites, which intrude Mesoarchean granitoids and form a NE-SW elongated pluton with subordinate lenses E-W oriented showing subvertical (70-80°) foliation. They consist of leucocratic rocks (M' = 21.1 - 32.9) with well-preserved magmatic textures and medium- to coarse-grained. The main mafic phases are pyroxene [enstatite/ferrosilite and augite/diopside (Wo1En66Fs33 to Wo49En38Fs14)], amphibole [hornblende (0.88 ≥ Mg/(Mg+Fe2+) ≤ 0.43)], and biotite [0.68 ≥ Fe/(Fe + Mg) ≥ 0.31]. These rocks are considered syntectonic plutons emplaced in a postcollisional setting, which underwent dynamic recrystallization controlled by subgrain rotation (SGR; 400-450 °C) in a sinistral transpressive deformational regime driven by pure shear. The granite-charnockite association and gabbronorite present very similar geochemical behavior: magnesian affinity [whole-rock 0.8 ≥ FeOt/(FeOt+MgO) ≤ 0.5], calc-alkaline and high-K calcic-alkaline trends and metaluminous character. Magma ascent and emplacement are reconstructed as a singlestage process with decreasing temperatures. Crystallization temperatures range from 1100 to ~700 °C for pyroxenes, and 809 to 713 °C for amphiboles. Calculated crystallization pressures were 190 to 310 MPa resulting in crystallization depths of 7.0 to 10.5 km. Observed mineral assemblages and compositions of the main mafic minerals imply crystallization under relatively oxidizing conditions (NNO -9.8 to -12.6). H2O contents ranging from 4.1 to 6.5 wt% and indicates that water played an important role in the magmatic evolution of the studied rocks. Hydration was responsible for differences in the modal contents of monzogranite varieties. Gabbronorites were probably formed by partial melting of depleted mantle source (low HFSE), and orthopyroxene-bearing granitoids originated through fractional crystallization from magma similar in composition to gabbronorite.
Acesso aberto (Open Access)
Chemical and mineralogical characterization of portuguese ceramic tiles in the historic center of São Luís do Maranhão (Brazil): an approximation of the mineralogy and firing temperature of the raw materials
(2013-03) MERCURY, José Manuel Rivas; PEREIRA, Domingos de Jesus Costa; VASCONCELOS, Nazaré do Socorro Lemos Silva; CABRAL JÚNIOR, Aluísio Alves; ANGÉLICA, Rômulo Simões
This work involved the first-ever characterization of antique Portuguese ceramic wall tiles in the Historic Center of São Luis do Maranhão, Brazil. The tiles were characterized by optical microscopy, X-ray diffraction (XRD) and chemical analysis to identify the possible raw materials used in the fabrication process, as well as the firing temperature of these materials. The results indicate that the microstructure of these materials consists of pores of varying sizes with calcite incrustations and quartz grain sizes smaller than 500 µm distributed in a pinkish yellow matrix, which were identified by XRD as calcite, gehlenite, wollastonite, quartz, and amorphous mineral phases. Based on this information, it can be inferred that the original raw materials probably consisted of a mixture of kaolinitic clays (Al2O3•2SiO2•2H2O) rich in calcium carbonates and quartz, or mixtures of kaolinitic clays, quartz and calcite, which did not reach the pre-firing temperature of 950oC.
Acesso aberto (Open Access)
Contrastes químicos, mineralógicos e de fertilidade entre solos tipo terra preta arqueológica: sítio da Mata, no limite Oriental da Amazônia, e sítio Porto de Santarém, no Baixo Amazonas
(Universidade Federal do Pará, 2012-06-18) SILVA, Uibirá Sena; KERN, Dirse Clara; http://lattes.cnpq.br/8351785832221386; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
Dark Earth sites are usually found in Amazonian Region. They stand out for their great content of ceramic fragments, urns, and lithic artifacts. Their soils present higher fertility if compared with the neighboring soils. Amazonian Dark Earths origins are related to pre-historic human activity of people who lived in ancient settlements in Amazonian Region for long periods of time. Recent researches reveal that the ceramic fragments from those sites present fertility as high as the soils, and even higher; and for that reason, when the ceramics fragments are exposed to weathering conditions, they could constitute in a potential source of nutrients for the soils that surround them. This study investigated the properties of soils and ceramic fragments from two ABE sites in distinct regions within the Amazon: Sítio da Mata, in São Luís City, Estate of Maranhão, region of forest-savanna transition; and Sítio Porto de Santarém, at the Tapajós River’s outfall, a former rain forest area that is currently intensively urbanized. This research aimed to characterize and compare the material from both sites, and correlate them to de different geomorphologic contexts in which they’re inserted. In the Sítio da Mata was sampled material from the ABE soil profile and from adjacent soil profile, and in Sítio Porto de Santarém, was sampled material only in the ABE soil profile. The samples comprised both soil and ceramic fragments matrices. The material was subjected to particle size analysis (soil samples only), X-Ray Diffraction (XRD) analysis, total chemical analysis by ICP-MS/OES, and fertility parameters analysis. Phosphorus fractionation was also performed in aim to determine the phosphorus species (P-Ca, P-Fe-Al, and organic P) present in soils and ceramic fragments samples. This study investigated the properties of soils and ceramic fragments from two ABE sites in distinct regions within the Amazon: Sítio da Mata, in São Luís City, Estate of Maranhão, region of forest-savanna transition; and Sítio Porto de Santarém, at the Tapajós River’s outfall, a former rain forest area that is currently intensively urbanized. This research aimed to characterize and compare the material from both sites, and correlate them to de different geomorphologic contexts in which they’re inserted. In the Sítio da Mata was sampled material from the ABE soil profile and from adjacent soil profile, and in Sítio Porto de Santarém, was sampled material only in the ABE soil profile. The samples comprised both soil and ceramic fragments matrices. The material was submitted to particle size analysis (soil samples only), X-Ray Diffraction (XRD) analysis, total chemical analysis by ICP-MS/OES, and fertility parameters analysis. Phosphorus fractionation was also performed in aim to determine the phosphorus species (P-Ca, P-Fe-Al, and organic P) present in soils and ceramic fragments samples. ABE from both sites showed high contents of the sand fraction, and soil texture varied from silty-loam to loam sand in Sítio da Mata and sandyloam in the entire ABE profile in Sítio Porto de Santarém. Mineralogical composition in both soils showed no significant differences: they consist most of quartz and kaolinite as primary mineral phases, and anatase and muscovite as accessory mineral phases. Chemical analysis reveal that the soils are composed most for SiO2 and Al2O3, confirming the mineralogical results, and Fe2O3 and TiO2 in minor quantities. P2O5, CaO, K2O and MgO are present in amounts below 0,5%, however, they show higher values in the soils from Sítio Porto de Santarém if compared to Sítio da Mata. Among the trace elements analyzed, only V, Cu, Zn, Sr and Ba stand out, and also show higher values in Sítio Porto de Santarém’s soils. Amounts and distribution patterns for Rare Earth Elements (REE), when normalized by condrits, are similar in both sites, showing enrichment of Light REE, strong positive anomaly for Ce, and negative anomaly for Eu. Differences only in the available P, Ca2+ and Mg2+ contents, although in relatively low values, suggest different anthropic influence over the pre-ABE soils. ABE soils from Sítio Porto de Santarém show higher fertility given for the higher contents of available P, ranging from 72,9 to 305,7 mg Kg-1, and Ca2+, ranging from 3,52 to 5,16 mg Kg-1, compared to 5,4 to 12,7 mg Kg-1 of P content and 0,96 to 2,31 mg Kg-1 of Ca2+ content in Sítio da Mata’s soils. Cation Exchange Capacity (CEC), sum of bases, base saturation and soil organic matter (SOM) were also higher in ABE from Sítio Porto de Santarém. Ceramic fragments from both sites are composed by quartz and metakaolinite, and also illite and anatase. Albite and microcline were detected only in ceramic fragments from Sítio Porto de Santarém. Therefore, they are composed mainly by SiO2 and Al2O3, and in smaller amounts, by Fe2O3 and TiO2. At Santarém, however, ceramic fragments contain also high amounts of P2O5, ranging from 3,49% to 5,37%, and the values for CaO, K2O, Na2O, Cu, Zn, Sr and Ba exceed those from Sítio da Mata. The contents and distribution pattern for REE are similar in ceramic fragments from both sites, with enrichment of LREE, positive anomaly for Ce and negative anomalies for Eu and Ho. Therefore, the ceramic fragments from both sites are mineralogicaly distinct, although they’re immersed in a similar soil matrix. The presence of phosphorus is compatible with others ceramic fragments found in different ABE sites. The fertility of ceramic fragments from Sítio Porto de Santarém showed better rates, with slightly higher pH if compared to ceramic fragments from Sítio da Mata, higher amounts of available Ca2+, K+ and mainly available P, besides higher CEC, sum of bases and base saturation, corroborating the higher fertility of the soils from Sítio Porto de Santarém. Phosphorus fractionation shows that in soil matrix from the studied sites, phosphorus is mainly related to organic compounds, while in ceramic fragments matrix, it is mainly related to nonapatite inorganic compounds. Apatite phosphorus is present in small amounts in both soil and ceramic fragments matrices. Therefore, it is likely that phosphorus present in organic material discarded by ancient people, as various kind of bones, among others, when submitted to tropical pedogenesis, were gradually dissolved, releasing phosphorus, which was partially fixed as Fe-Al phosphates, common mineral phases in tropical soils, as well as organic matter, abundant in ABE, respectively representing the nonapatite inorganic phosphorus and the organic phosphorus fractions.
Acesso aberto (Open Access)
Distribuição de metais base e preciosos em solos, da área de San Javier-San Ramon, Santa Cruz de la Sierra, Bolívia.
(Universidade Federal do Pará, 1996-10-22) UZQUIANO ESPINOZA, Francisco German; RAMOS, José Francisco da Fonseca; http://lattes.cnpq.br/8189651755374537
Acesso aberto (Open Access)
Efeito de aditivos no comportamento reológico do rejeito da bauxita
(Universidade Federal do Pará, 2015-03) GONÇALVES, Silvane Gonçalves e; BRUM, Sebastião Martins; FELIPE, Augusta Maria Paulain Ferreira; SOUZA, José Antônio da Silva; FERREIRA, Keylla Castro
In the bauxite mining in Parogominas, PA, Brazil, tailings are discarded in the processing with 33.5% of solids content and small particle size with D50 below 5 µm. These factors contribute to this suspension basically formed by silicoaluminates, with high concentrations of kaolinite clay, increase the viscosity and the yield stress, these factors are important during the pumping. It was performed granulometric analysis and determined the chemical and mineralogical composition of the material. It was studied the use of the sodium hexametaphosphate and polyacrylamide 25% anionic to decrease the viscosity. The result show that the viscosity decrease with use of 23.8 g/ton for the polyacrylamide and 101.75 g/ton for the sodium hexametaphosphate. The particle size and the pH have influence in the behavior of the additives.
Acesso aberto (Open Access)
Efeitos das variações sazonais do clima tropical úmido sobre as águas e sedimentos de manguezais do estuário do rio Marapanim, costa nordeste do Estado do Pará
(Instituto Nacional de Pesquisas da Amazônia, 2008) SILVA, José Francisco Berrêdo Reis da; COSTA, Marcondes Lima da; VILHENA, Maria do Perpétuo Socorro Progene
To evaluate the short period climatic variations impact over Amazonic mangrove ecosystem, studies were carried out on the northeast coast of Para State. Sediments, surficial and interstitial waters were collected and examinated throughout salinity, pH and Eh (mV) measurements; mineralogical determination using X-ray diffraction and electronic microscopy. Chemical analysis of dissolved sulfides, sulfate and chloride, among others were made in samples collected seasonally, under spring and neap tides conditions. The seasonal chloride variations in the interstitial waters shows 20 g/l during the dry season and less of 10 g/l in the season; the concentration in surficial are higher at neap tides (rainy season) and spring tide (dry season). The dissolved sulfides were found only at 10 cm, indicating sediment exposure to the atmospheric oxygen advectives fluxes. The dissolved iron rates increases between 0-10 cm and the pH tends to neutrality. The saturation of interstitial waters at dry season is indicated by evaporitic minerals: gypsum and halite. The pluviometric variations are responsible by gradual changes in the nutrient and physical chemical properties of surficial and interstitial waters, into the saline equilibrium control at coastal waters, in the salinization and desalinization of sediments and the distribution of mangrove vegetation at the estuary. The prolonged exposure of sediments during the dry season and the morphological characteristics contribute to the total or partial oxidation of surficial sediments, modifying the mineralogy of sediments and the physical chemical characteristics of interstitial waters.
Acesso aberto (Open Access)
Eflorescência salina na igreja de Santo Alexandre, Belém - PA
(Universidade Federal do Pará, 2015-09) LOUREIRO, Alexandre Máximo Silva; ANGÉLICA, Rômulo Simões; SANJAD, Thais Alessandra Bastos Caminha; OLIVEIRA, Mário Mendonça de; COSTA, Marcondes Lima da
The structural masonry of the historical monuments of the city of Belém, Brazil, is made of stones and solid bricks fixed with lime mortar, which is affected by different pathologies, including salt efflorescence and moisture action. Some authors explain that these two agents cause layer detachment, mortar pulverization, cracks and a whitened appearance. This aim of this study was to identify the degradation process affecting the masonry of the right transept of the Church of Santo Alexandre, using instrumental analytical techniques. Laboratory analyses were used in order to understand the saline efflorescence process, the material damage it causes and the main kinds of salts. The first step in the study was to map out the masonry and the damage, showing the current situation and the most damaged areas. That was followed by a physical characterisation through an analysis of mortar particle sizes and proportions, analysis of masonry moisture contents, chemical characterisation -qualitative and quantitative chemical analysis of soluble salts, and mineralogical characterisation by X-ray diffraction. The techniques applied were effective and contributed to the achievement of a correct diagnosis, guiding the type of interventions required to solve the problem.
Acesso aberto (Open Access)
Estudo físico-químico de hidróxi-fosfatos e minerais associados ocorrentes na Chapada de Pirocaua (MA) e no Morro de Jandiá (PA)
(Universidade Federal do Pará, 1982-12-29) REYMÃO, Maria de Fátima Fernandes; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
A lateritic profile rich in alumino-calcic and aluminum hidroxi-phosphates (Pírocaua, MA), and another also rich in alumino-oaloio and containning iron and calcium hidroxi-phosphates (Jandiá, PA) has been investigated in order to elucidate the formation of the secondary minerals and the trace element behaviour during tropical weathering. For such purposes it was decided to use X-ray diffratometry and chemical analysis and it was pointed out the applicability of infrared absorption spectroscopy: and differential thermal analysis for the mineral characterization. In order to relate the geochemical alterations it was included a theoretical thermodynamic study. lnfrared absorption spectroscopy and differential thermal analysis have been demonstrated to be valuables methods for studying minerals. Results are presented which demonstrate the usefullness of these techniques. These studies show that it is now possible to correlate differential hermal analysis and infrared data with that from other techniques (chemical analysis, X-ray diffraction patterns) and that the methods yields valuable supplemental information. Theoretical calculations and the use of thermodynamic data (standard free energie and solubility products) reveal some important conclusions about chemical equilibria, mineral formation, solubility and stability relations.
Acesso aberto (Open Access)
Estudo geoquímico do sistema hidrotermal relacionado à mineralização cuprífera da área Bahia, Serra dos Carajás, Pará
(Universidade Federal do Pará, 1989-10-24) RIBEIRO, Ana Maria Rodrigues; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983