Navegando por Assunto "Arenito"

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Análise faciológica das formações Poti e Piauí (carbonífero da Bacia do Parnaíba) na Região de Floriano-PI
(Universidade Federal do Pará, 2000-07-20) RIBEIRO, Cleive Maria Monteiro; GÓES, Ana Maria; http://lattes.cnpq.br/2220793632946285
Acesso aberto (Open Access)
Arenito zeolítico com propriedades pozolânicas adicionadas ao cimento Portland
(Universidade Federal do Pará, 2011-08-29) PICANÇO, Marcelo de Souza; BARATA, Márcio Santos; http://lattes.cnpq.br/7450171369766897; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The proper use of pozzolans enables the production of special cements with lower manufacturing cost and higher durability in comparison with cements without mineral additions. It also enables significant gains in productivity and extending equipments life in the fabric, limestone reserves, and also helping in the reduction of CO2 release into the atmosphere. Zeolites have been used as pozzolanic material in mixtures with Fuller’s Earth and water in buildings from the ancient Roman Empire. Nowadays, there are many discussions involving pozzolanic reactivity of natural zeolites in the incorporation of Portland cement. In the Northeastern region of Brazil, sedimentary zeolites related to sandstones of the Parnaiba Basin wer discovered by the Geological Survey of Brazil in the 2000s. These sandstones are mainly composed by quartz, natural zeolites (estilbity) and clay (smectite). Preliminary studies have pointed that this sandstone may be used as pozzolanic material in Portland cements. The material must be previously sieved to remove quartz and thermally activated, since stilbite is a zeolite with low pozzolanic activity. The main objective of this work is to advance the understanding of the factors that govern the quality and performance of Portland cement modified with this zeolitic sandstone. For this work the structure was divided into three main stages, related to three specific objectives, so that the results are presented in the form of three scientific papers, described as follow: - Evaluation of the natural pozzolanic activity of the zeolitic sandstone to be used as mineral addition in the Portland cement. - The determination of which particle size provides the highest zeolite and smectite concentration, besides the calcination temperature that leads to a higer pozzolanic activity. - The establishing of the best amount of thermally activated zeolitic sandstone to be incorporated as a mineral addition in the Portland cement. During all phases, different instrumental techniques were used for the chemical and mineralogical characterization of the starting materials and products (sandstone + lime mortar, mortar with Portland cement + sandstone + Portland cement pastes sandstone), including: spectroscopy x-ray fluorescence, x-ray diffraction, thermal analysis and scanning electron microscopy. Heat-flow calorimetru assays were carried out to evaluate the physical properties, besides mechanical testing of compressive strength of cement mortars Porltand. In the first stage of the experimental program, the zeolitic sandstone was sieved into different granulometric fractions in order to remove the inert phases (quartz and other minerals), and concentrate the zeolite for further pozzolanic assays. In the second stage, after the first characterization of the samples, we used the zeolitic sandstone that passed in the # 200 and # 325 sieves and calcined at temperatures of 150º C, 300° C and 500° C. Finally, in the third stage, # 200 fraction was calcined at 500 ° C and mixed in different proportions (10, 20 and 30%) in the mortar. The results of the first stage, which culminated in the first article showed that the zeolitic sandstone accelerated the hydration of Portland cement due to the extreme fineness of the material. The sandstone showed pozzolanic activity, and estilbite is the main responsible for this behavior. However, the reactivity was slightly lower than the minimum required to be employed as pozzolan on an industrial scale. Additional studies are needed to ascertain if the thermal treatment between 400° C and 300o C could increase the pozzolanic activity of the sandstone due to the destruction of the crystalline structure of both estilbite and smectite. For the second stage, the results showed that the # 200 fraction was the most suitable because of the higher estilbite concentration (15%) in comparison to the # 325 ssample (2%). The calcination temperature of 500º C has provided the highest pozzolanic activity due to more effective destruction of the crystalline structure of both estilbite and smectite. More moderate temperatures of 150° C and 300° C were not enough. Mortars with the 200 # sample calcined at 500 ° C reached values smaller as those required for a material to be considered as a pozzolane, in this case, 6 MPa for mortar of lime and 75% for the pozzolanic activity index (IAP). The results showed from the third stage showed that the AZ2-3 mixture (10% of zeolitic sandstone incorporated in Portland cement type CPI-S), showed the best result of compressive strength and mineralogical properties of the samples suitable for the production a commercial cement type CPII-Z. In general, one concludes that the zeolitic sandstone from northeastern Brazil has the potential feasibility of producing a CPII-Z cement, whose pozolan contents ranges from 6 to 14% in the Portland cement, according to the ABNT - NBR 11578. Although the strength of the mortar with 10% of AZ2- 3 has reached resistance values close to the reference mortar with 100% of CPI-S, further studies should be carried out in order to find better proportion of sandstone and to meet the requirements for future commercialization.
Acesso aberto (Open Access)
Atividade pozolânica de arenito zeolítico da região Nordeste do Brasil
(2012-06) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
In northeastern Brazil, sedimentary zeolites occur associated with sandstones of the Corda Formation (Parnaiba Paleozoic Basin), discovered in the 2000s. These sandstones are composed of quartz, natural zeolites (estilbite) and clay minerals (smectite). Preliminary studies have shown that this sandstone can be used as a pozzolanic material in Portland-cement-based systems after the material has been sieved to remove the quartz and after thermal activation because the estilbite has low pozzolanic activity. The main objective of this study was to determine the best particle size distribution that yields the highest smectite and zeolite concentration, besides the best temperature for higher pozzolanic activity. The experimental program employed the zeolitic sandstone passing through a #200 and #325 mesh sieve and calcination at the following temperatures: 150°C, 300°C and 500°C. Chemical analysis of the sieved samples was carried out by X-ray fluorescence spectroscopy and X-ray diffractometry, while mineralogical characterization was done by X-ray and thermogravimetric analysis and thermogravimetry..To assess reactivity, calorimetry driving and mechanical tests for pozzolanic activity in hydrated lime and cement Porltand were performed. The results showed that the sample sieved through at #200 mesh was the most suitable because it had a higher concentration of estilbite and a higher percentage of material seived compared to the sample sieved at #325 mesh, 15% and 2% respectively. The 500°C calcination temperature was accompanied by increased pozzolanic activity due to changes in estilbite and smectite cristalinity; the more moderate temperatures of 150°C and 300°C were not sufficient to achieve similar results. The mortars with sandstone sieved at #200 mesh and calcinated at 500°C reached the minimum limits required for a material to be considered as pozzolanic, i.e, 6 MPa for hydrated lime mortars and 75% for the pozzolanic index activity (PAI).
Acesso aberto (Open Access)
Avaliação preliminar do emprego de arenito zeolítico da região nordeste do Brasil como material pozolânico para cimento Portland
(2011-12) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
Natural zeolites usually exhibit pozzolanic activity without any additional treatment, e.g. thermal activation. They have been used for building since the ancient Roman Empire times in the production of hydraulic cements and concretes. Nowadays, there are many discussions involving the natural zeolites pozzolanic reactivity in the incorporation of the Portland cement composition. The appropriate use of pozzolans enables the production of special cements with lower manufacturing cost and with a greater durability in comparison with the corresponding cements without addition. In Brazil, zeolite consumption comes either from the importation of foreign countries or synthetic products. No zeolite mine is available in the country and only few geological occurrences were already described in the literature without any commercial interest. In northeast Brazil, the Geological Survey (CPRM) discovered zeolite-bearing sandstones related to Cretaceous sedimentary rocks of the Parnaíba Paleozoic Basin. The main purpose of this paper is to evaluate the possible use of such sandstones as pozzolan for using in Portland cements (CPI-S). A bulk sample of the zeolitic sandstone (AZ) was collected in the field. In the laboratory, preparation included drying, milling and sieving at the following grain-size fractions, in order to remove quartz and concentrate the zeolite: 100# (AZ-1), 200# (AZ-2) and 325# (AZ-3). After mineralogical evaluation, the AZ-2 fraction was selected for further analysis and assays. The experimental study was mainly based on mineralogical characterization, including: X-ray diffraction (XRD), chemical analysis and heat flow calorimetry, besides pozzolanic activity assay and compressive strength. The results show that the mineralogical composition of the zeolitic sandstone is mainly quartz, zeolite (stilbite) and smectite. Stilbite is the main pozzolanic phase, and the smectite can also play an important role. The hydration of the Portland cement was accelerated due to the very fine grained nature of the material. Meanwhile, the reactivity obtained was slightly below the standard requirements to be used in industrial scale. Additional studies should be carried out in order to evaluate if a further thermal treatment (between 300 °C and 500 °C) may increase the pozzolanic activity due to the stilbite destruction around this temperature. The same happens with kaolinite that needs thermal treatment above 550 ºC to convert to the amorphous phase metakaolin in order to be used as one of the most commons pozzolans in the cement industry. The main purpose was to contribute for the production of an alternative kind of cement which produces less pollution to the environment (CO2 decrease in the atmosphere) with cost saving. In addition, it is expected to contribute for the exploitation of the sedimentary zeolites occurrences which have been relatively well studied from a geological point, but are still not mined.
Acesso aberto (Open Access)
Cimentos Portland aditivados com arenito zeolítico com propriedades pozolânicas
(2014-06) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
The proper use of pozzolans enables the production of special cements with lower manufacturing cost and higher durability in comparison with cements without mineral additions. It also enables significant gains in productivity and in equipment service life in the factory as well as reduce the CO2 emission into the atmosphere. Zeolites have been used as pozzolanic material in mixtures with Fuller's Earth and water in buildings from the ancient Roman Empire. Nowadays, there are many discussions involving pozzolanic reactivity of natural zeolites in the incorporation to Portland cement. In the Northeastern region of Brazil, sedimentary zeolites related to sandstones of the Parnaiba Basin were discovered by the Geological Survey of Brazil in the 2000s. These sandstones are mainly composed by quartz, natural zeolites (estilbity) and clay (smectite). Preliminary studies have pointed that this sandstone may be used as pozzolanic material in Portland cements. The material must be previously grinded to remove quartz and thermally activated, since stilbite is a zeolite with low pozzolanic activity. The aim of this study was to evaluate the ideal amount of thermally activated zeolitic sandstone to be incorporated in the Portland cement in order to improve its mechanical and mineralogical properties. In the laboratory, the < # 200 fraction of the zeolitic sandstone was calcined at 500 º C. Chemical and miner-alogical analysis were carried out by X-ray fluorescence spectroscopy (XRF) and X-ray Diffractometry (XRD), respectively. The hydration behavior of the cements was evaluated using heat-flow calorimetry, besides thermal analysis and XRD. To evaluate the physical properties, mechanical testing of compressive strength in cement mortar Portland with different proportions of sandstone was carried out. The results showed that the AZ2-3 zeolitic sandstone with the proportion of 10% incorporated in Portland cement type CPI-S, showed the best result of compressive strength and mineralogical properties of the samples suitable for the production of CPII-Z type commercial cement.
Acesso aberto (Open Access)
Fáceis sedimentares e evolução diagenética dos arenitos da Formação Faro (Eo-Carbonífero) da Bacia do Amazonas
(Universidade Federal do Pará, 1993-01-11) AMADOU, Ba Ibrahim; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553
Acesso aberto (Open Access)
Fácies costeiras dos depósitos itapecuru (cretáceo), região de Açailândia, Bacia do Grajaú
(Universidade Federal do Pará, 1999-11-17) ANAISSE JUNIOR, José; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553
Acesso aberto (Open Access)
Fácies e proveniência de depósitos costeiros da Formação Raizama: evidências do registro Ediacarano-cambriano na faixa Paraguai, região de Nobres, Mato Grosso
(Universidade Federal do Pará, 2014-03-10) SANTOS, Hudson Pereira; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Siliciclastic rocks from the Raizama Formation, a basal unit of the Alto Paraguai Group, from the Ediacaran-Cambrian interval (635-541 Ma), is discontinuously occur distributed along the southern margin of the Amazonian Craton within the Paraguay Fold Belt northern segment, west-central of Brazil, Mato Grosso state. This Group unconformably overlies carbonate shelf deposits of the Araras Group, where evidence of Marinoan glacial event (635 Ma) was recorded. The Alto Paraguai Group represents the final stages of the collision between the Paranapanema and Amazonian blocks, leading to the closure of the Clymene Ocean (540-520 Ma). The Raizama Formation is approximately 570 m of thickness and is composed by mudstone, fine to coarse sandstones, and sandstones with dolomitic cement previously interpreted as fluvial-coastal deposits distributed in the lower member (270 m) and upper member (300 m). The facies and stratigraphic studies of this unit in the Nobres region, Mato Grosso state, were mainly focused on the outcropping section of 600 m in the bed of Rio Serragem II, which includes the Serra do Tombador waterfall. In this stratigraphic section, 17 sedimentary facies were described and grouped into five facies association (AF), representative of a progradational coastal sequence beginning with lower shoreface deposits, overlying in correlative conformity the shelf carbonate deposits of the Serra do Quilombo Formation (Araras Group). The AF1 facies consists of sandstones with planar lamination and wave-ripple cross-lamination (microhummocky), individualized by layers of laminated pelite interpreted as lower shoreface deposits. It stands out in the AF1 the first occurrence of centimetric bioturbed levels of Skolithos in Neoproterozoic-Cambrian deposits in the Paraguay Belt. The AF2 facies is composed by sandstones with swaley cross-stratification and plane bedding interpreted as upper shoreface deposits. The AF3 facies is composed by sandstones with tangential and trough cross-stratification with drapes of siltstone/very fine sandstone representative of channel and subtidal bars deposits. The AF4 facies is characterized by sandstones with tangential and sigmoidal cross-stratification, planar to low angle cross-lamination, rhythmites very fine sandstone/siltstone with flaser bedding and mudcracks, organized in metric tidal flat shallowing upward cycles. The AF5 facies is comprised of sandstone with trough cross-bedding characterized by common lags at the base of the association, sandstone with planar to low-angle cross-stratification, interpreted as distal braided rivers, in part reworked by waves. Detrital zircon grains were obtained from AF3 and dated by U-Pb method, resulting in an age 1001±9 Ma interpreted as the age of the maximum deposition of Raizama Formation. Combined with this analysis, the NE-SE paleocurrents show that source area of these sediments would be the Sunsas Fold Belt, SW of the Amazonian Craton not being discarded contributions coming from the NW part of this Craton. The obtained Mesoproterozoic age has predominantly served to unravel the provenance of Raizama Formation. Whereas dating from the base of Araras Group, around 627-622 Ma, associated with the clear presence of the ichnogenus Skolithos, suggests that the age of this unit is closer to the limit with the Lower Cambrian. Trace fossils from the Proterozoic are characterized almost exclusively by horizontal traces, while vertical bioturbation are virtually absent throughout the Neoproterozoic. This inference is confirmed by the maximum age of 541 Ma obtained for Diamantino Formation, which overlies the studied unit. The radiometric data combined with paleoenvironmental interpretation, including the record of the first burrowing activities in Paraguai Fold Belt, opens up perspectives to understand in greater detail the sequence of events that typify the Ediacaran-Cambriam boundary strata of Brazil, still poorly known.
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Litofácies e evolução diagenética dos arenitos da formação Monte Alegre na região do rio Tapajós, Bacia do Amazonas
(Universidade Federal do Pará, 1989-11-23) TORRES, Admilson Moreira; TRUCKENBRODT, Werner Hermann Walter
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Paleoambiente e icnofósseis do arenito guamá (Siluriano), regiões de São Miguel do Guamá e Irituia, estado do Pará.
(Universidade Federal do Pará, 2019-07-08) MARTINS, Taynara Cristina Matos; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
The Guamá Sandstone is a restricted sedimentary unit that occurs in the Bragantina Platform, mainly in the São Miguel do Guamá and Irituia regions northeast of the state of Pará still needs a better geological detail. It is characterized by thick layers of well-rounded and selected, mature medium-grained quartz-sandstone with medium granulometry, well rounded, well selected and with high degree of textural and compositional maturity. Based on the petrographic, faciological and ichnological characteristics similar to the quartz sandstones of the Nhamundá Formation (Amazon Basin), a Silurian age for the Guamá Sandstone has been suggested. Commonly, the quartz-sandstone layers have a massive appearance and few preserved primary sedimentary structures (e.g., cross-stratified ribbed stratification, plane-parallel stratification and wavy and planar lamination). The facies association indicates that the studied deposits were formed in a sandy coastal region that covered the foreshore and shoreface zones. In the Guamá Sandstone the icnoespecies Skolithos linearis, Psammichnites isp., cf. Schaubcylindrichnus coronus, single vertical tube undetermined and Lingulichnus verticalis were identified, they commonly compose a mixture of the Cruziana and Skolithos ichnofacies. Periodic energy changes and sedimentation rate in the depositional environment are suggested by the regular distribution between Skolithos and Psammichnites in the sandstone layers. Skolithos occurs, generally, in massive layers and can reach up to 1 meter in length indicating high energy conditions and/or high sedimentation rates. While Psammichnites occur at the top of these layers and suggest lower energy and/or low sedimentation rate. Skolithos exhibit a bioturbation index (ii) ranging from 2 to 3 (5-40%). The Psammichnites exhibit ii between 4 and 5, which indicate a 40 to100% reworking of the substrate by excavating organisms. The low ichnodiversity and high abundance of ichnofossils suggest stressful conditions during the depositional period. The mixture of Skolithos-Cruziana ichnofacies is commonly associated with coastal marine environments of brackish waters. The reason for environmental stress conditions related to the presence of brackish water could be the influx of melting/defrosting waters in periglacial environments. The correlation of the Guamá Sandstone with the Silurian deposits of the Nhamundá Formation supports this idea, as this unit exhibits glacial, post-glacial, and coastal deposits that record the Silurian glaciation of Gondwana. Therefore, the Guamá Sandstone can be considered as the record of sandy coastal deposits influenced by the glaciations that affected the Amazon region during the Lower Silurian.
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A sucessão siliciclástica-carbonática neocarbonífera da bacia do Amazonas, regiões de Monte Alegre e Itaituba (PA)
(Universidade Federal do Pará, 2010-03-14) LIMA, Hozerlan Pereira; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Neocaboniferous deposits of Morrowanian age in the Amazon Basin, northern Brazil, characterize the transition zone between Monte Alegre (siliciclastic rocks) and Itaituba (carbonate rocks) formations. The outcrop-based facies and stratigraphic analyses of this up to 40m thick succession, exposed in the Monte Alegre and Itaituba regions, State of Pará, allowed the recognition of five facies associations (FA), representative of a transitional desertic to coastal system, comprising: eolian dune/interdune (FA1), sandy sheet/wadi (FA2), lagoon/washover (FA3), beach/tidal flat (FA4) and lagoon/tidal delta (FA5). FA1 contains bimodal fine to medium-grained sandstone with medium-scale trough cross-stratification, subcritically climbing translatent stratification and inversely graded lamination (dune deposits). Massive fine sandstones with root marks suggest development of paleosols, while adhesion warts indicate eolian grain migration on wet interdune surface. FA2 comprises fine to medium-grained sandstone with even-parallel stratification and subcritically climbing translatent stratification, related to deflation, while fine to medium-grained sandstone with tangential and recumbent-folded cross-stratification and convolute bedding suggest migration of high-energy ephemeral rivers. FA3 with laminated mudstone and fine-grained sandstone with climbing-ripple cross lamination, hosting the ichnofossil Palaeophycus, suggests a low-energy environment of lagunar/washover type. FA4 is characterized by fine to medium-grained sandstones with planar and low-angle cross-stratification, interbedded with lenticular dolomite, locally truncated by fine to medium-grained sandstones. These facies correspond to the zone of swash and backwash on beach environment, locally cut by small channels, while the carbonate is interpreted as precipitated in ponds. FA 4 also comprehends mudstones with mudcracks and mud curls as well as small to medium-scale planar cross-bedded sandstones with mud drapes lining foresets and reactivation surfaces, suggesting migration of sandwaves in intertidal zones. FA5 is represented by dolomitized limestones (mudstones, wackestones, packstones and grainstones) containing vuggy and moldic porosities. Bioclasts include brachiopods, echinoderms, foraminifers, ostracodes, bryozoans, trilobites, mollusks and non-fragmented corals, and furthermore the trace fossil Thalassinoides. Additionally, this facies association comprises conglomerates with pebbles of dolomitized limestones, fine-grained sandstones with low-angle cross-stratification and reactivation surfaces, locally overlaid by fine sandstones with sigmoidal cross-stratification and climbing cross-lamination, which were interpreted as tidal inlet and tidal delta deposits. The facies/microfacies associations and paleontological data presented here point to a lagoonal environment, connected in part to a coastal desert zone, and characterize the transition between Monte Alegre and Itaituba formations. The abundance of fine sands with rounded grains in carbonate facies is consistent with siliciclastic influx from the desert adjacent to coastal environment. Warm tropical conditions for the environments can be inferred from the limestones and their diverse fauna as well as from the clay minerals, principally smectite. The interbedding of siliciclastic and carbonate rocks which characterizes the end of the deposition of the Monte Alegre Formation and the beginning of the sedimentation of the Itaituba Formation justifies a unique system representation for this interval.
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Textural patterns, mineralogy, and chemistry of sandstone-related Calçadinha chalcedony (Piauí, Brazil)
(Universidade Federal do Pará, 2016-09) COSTA, Marcondes Lima da; ALENCAR, Quézia da Silva; GOMES, Érico Rodrigues; ALMEIDA, Henrique Diniz Farias de; OLIVEIRA, Sarise Kamanda de
Paleozoic sandstones of the Parnaíba Basin, in addition to hosting opal deposits, also have occurrences of chalcedonies with potential for mineral and ornamental handicrafts, in addition to assisting the understanding of the geological evolution of the basin. However, the chalcedonies were not investigated yet, and this study intended to fulfill this gap by the investigation of the chalcedonies of Calçadinha in Piauí. Fieldwork, microtexturals analysis, X-ray diffraction and scanning electron microscopy with energy dispersive spectrometry, chemical analysis, and gemological assessments were developed. Four distinct types of chalcedonies have been distinguished. They stand out for their well distribution of Fe and Mn dendrites, which involves opal nodules, and contains microcavities with well-formed microcrystalline quartz, nontronite, and palygorskite. The mesoscopic features of these chalcedonies and cabochon and free forms cutting show potential for use in mineral crafts and semi-jewels. As expected, the chalcedonies are dominated by high contents of SiO2, besides the low and variable contents of Al2O3, Fe2O3, MgO, and TiO2. Among trace elements that show high Ba contents, bound in barite, seem also to be a geochemical signature of the country sandstones in Parnaíba basin. These chalcedonies were formed during the partial solubilization of SiO2 of sandstones, which was promoted during their tectonic formation in faults and fractures zones.