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)
Avaliação da influência dos cátions Na+, Ca2+ e Mg2+ na desativação de Ca, Mg-Bentonitas
(Universidade Federal do Pará, 2015-04-28) CARMO, Andre Luiz Vilaça do; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
In Brazil there is no occurrence of sodium bentonite, because of that, companies that explore this mineral raw material using a denominated sodium activation process, which is the exchange of cations in the interlayer space by Na+. Through this process, the bentonite present considerable improvements in their properties rheologies. However, after some time, these properties decline, which has been called deactivation. Thus, the objective of this study was to evaluate the influence of cations Na+, Mg 2+ and Ca2+ in the bentonite deactivation. For this, three bentonite considered calcic, from the state of Paraíba, and a magnesian, coming from the state of Maranhão, were studied in its natural form, activated and washed. The mineralogical phases of the samples were identified by X-ray Diffraction (XRD), chemical composition by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and cations in the interlayer by Cation Exchange Capacity (CEC). The rheological properties’ study was carried out by swelling. The XRD patterns showed that the dioctahedral smectite is the dominant mineral phase. There was the improvement in swelling results of all bentonite after the sodium activation, as well as subsequent decrease in the swelling value over 95 days (deactivation). Only one of the bentonite remained activated. The swelling results of washed bentonite showed increased for approximately the first 35 days, with subsequent decrease. The chemical composition results showed that a small amount of Na+ is removed from the washed bentonite. Furthermore, these results indicate that not only Na+ influences the swelling, but also Ca2+ and Mg2+ cations.
Acesso aberto (Open Access)
Caracterização geológica da suíte ofiolítica Serra do Tapa, SE do Pará – Cinturão Araguaia
(Universidade Federal do Pará, 2015-04-30) BARROS, Luisa Dias; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
In northern Araguaia Belt (CA) along its low-grade metamorphic domain, the region known as Serra do Tapa, between the municipalities of Sapucaia and Xinguara, SE Para exposes one of the largest CA ophiolite bodies interpreted as fragment of oceanic lithosphere the Araguaia basin in Neoproterozoic. The Suite Ophiolitic Serra do Tapa (SOST), denominade in this work, is a set of elongated bodies with a length of 48 km with preferential orientation in the direction N-S. It represents a dismembered ophiolitic sequence comprising serpentinized peridotites, massive and pillow basalts, volcanossedimentary rocks, iron formation and cherts. All this set embedded through thrust zones in the metasedimentary rocks of low metamorphic grade of Formation Couto Magalhães. The serpentinized peridotites have dark or light green, coarse-grained and represent the basal portion of the stratigraphic sequence suite. Originally, the peridotites were probably the harzburgite and dunites type. The harzburgites have protogranular texture, with a marked presence of pseudomorphic textures bastite type and mesh, which result from orthopyroxene transformations; and olivine to lizardite, respectively. The dunites have mesh predominant texture, with the presence of fine chromite grains dispersed in the matrix composed of serpentine (lizardite). The volcanic unit of suite represented by massive basalt submarine flows and pillow structures. The basalts occur as homogeneous flows, massive and in the upper portions feature marked for pillow structure, and locally, breccia flow surface (hyaloclastites). The pillows have a zoning, where in the core consists of massive basalt greenish brown color, aphanitic with intersertal texture composed of crystals of plagioclase, volcanic glass and Clinopyroxene. At the edge zone are present glassy basalts of yellowish green color, aphanitics and quenching textures ultrafast as spherulites, and radial acicular crystals of plagioclase, textures type "swallowtail" and hollow sections. The hyaloclastites occur in the outer zone of the pillow and represent breccias surfaces basaltic. Finally, basalt glass is dark green color of the surface flows (interpillow zone). The volcanossedimentary interface sequence is the interaction between the basalt flows and pelitic sedimentary rocks. The tuffaceous mudstone consists of a pelitic matrix with lytic fragments of metabasalt stretched and broken. The sedimentary portion of the suite consists of iron formation and cherts and represent the chemical sedimentation records in deep-sea ocean environment, is the upper portion of this ophiolitic suite. Another important feature is the presence of sinistral strike-slip shear zones and dextral of kilometric extensions with preferential orientation NE-SW and EW. All structures truncated by normal faults of NW-SE direction. The rocks of Formation Couto Magalhães evidence of metamorphism is most obvious in slates and phyllites (sericite and chlorite formation) in serpentinized peridotites occurs generation of non-superposition serpentine pseudomorphs of pseudomorphs, the massive basalts, the metamorphic association is defined by ab + Tr act + Cl + Ep ± Stp; the paragenesis of these rocks indicate metamorphic transformation in greenschist facies low. For lithochemical studies were prioritized portions of the core of the pillow, which remained in many cases, the protected metasomatic transformations. Divergent data in some samples can be explained because they are samples closest to the edges of the pillows, which suffered intense transformation due to oceanic metamorphism. Geochemically, the basalts show subalkaline nature, tholeiitic compatible with the MORB type. Sr negative anomalies may indicate plagioclase retention during partial melting events from depleted mantle source. The ETR diagram shows slightly depleted behaviors of LREE and enriched in heavy REE and smooth Eu anomaly; and this pattern confirmed the reasons (La / Yb) N and (La / Sm) N <1 magmas also point to the N-MORB type. The evolution of the suite is on the development of oceanic Araguaia Basin with the generation of an old oceanic lithosphere to rise and perhaps upper mantle exposure, volcanism forming the deep ocean substrate and sedimentation (tuffaceous mudstone, banded iron formation and cherts). Later detachment processes of the substrate crust / mantle led to the tectonic inversion of the sequence, leading to compressional tectonic phase, which led to obduction of ophiolite bodies, generating a late thrust and transcurrent system with movement toward the Amazonia Craton, segmented the ophiolite bodies and mixing them with rocks Couto Magalhães Formation accompanied by regional metamorphism of greenschist facies low.
Acesso aberto (Open Access)
Cristaloquímica da sodalita Bayer derivada de bauxitas com alta sílica reativa de Paragominas-Pa
(Universidade Federal do Pará, 2016-05-24) MELO, Caio César Amorim de; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
In the Paragomina’s region, as well as the whole Brazilian north, gibbisitic bauxite deposits commonly shows high amount of kaolinite. The processing of this bauxites (called as High Silica Bauxites - BASR) became a challenge because in the conventional conditions of the Bayer process, the kaolinite is undesirably leached by NaOH solution, and then precipitated as sodalite. The formation of this phase brings a significant increase in process costs, both by increasing the processing time as the irreversible loss of NaOH robbed from the system to form sodalite, which is then discarded in the red mud. Given this metallurgical problem this study aimed to investigate the crystal chemistry of sodalite formed in conventional conditions of the Bayer process, so that, from these results, studies to reduce these losses of the process and facilitate the processing of BARS can be developed in the future. The materials investigated were kaolinitic gangues from 4 lithologies of an exploration well in Miltonia 3 mine (BN, BNC, BC and BCBA), as well as a kaolin from IMERYS S.A. The digestions were carried out in Teflon-lined, stainless steel autoclaves, using 1 g of solid material, 25 mL of NaOH solution and at a temperature of 150ºC in an oven. The NaOH concentration and the reaction time ranged from 2,5 to 5,0 M and 60 to 420 min, respectively. Then the solid material was characterized by XRD, DTA/TG, FTIR, SEM and ICP-OES. The results of the starting materials showed that the kaolin sample is essentially constituted by kaolinite, which has a high structural ordering degree. All the samples of kaolinitic gangue showed the same minerals: gibbsite, kaolinite, hematite, goethite and anatase. By the observation of the XRD patterns and DTA curves can be noted that the BN and BNC samples are more reactive than the others, possibly due a lower structural ordering degree and particle size. In the experiments with kaolin, it can be observed that are formed not one, but two sodalite phases, which coexist practically throughout the whole process and tending to an equilibrium phase. These two phases differs themselves by the amount and behavior of the NaOH and H2O molecules within the framework. The results of the refinments showed that these phases were: basic sodalita with cell parameter (ao) ~ 8,96 Å, which is predominant in the initial stages of the transformation, and hydrosodalite with ao ~ 8,85 Å dominant in the secondary stage (mainly in 180 min). The XRD results from kaolinitic gangues showed that in 60 min there was no full kaolinite/sodalite conversion, and the sodalite patterns in BN and BNC were more intense and well defined than BC and BCBA, confirming that these samples have more reactive kaolinites. The increase of the reaction time and NaOH concentration provided a slight increase of the structural sodalite order. It may be noted that in almost all experiments the only phase formed was basic sodalite. The exceptions were the lithologies: BCBA and BC, which hydrosodalite was formed in the highest time of reaction and NaOH concentration, thus showing that this phase is directly associated with a higher time, concentration and crystallinity of kaolinite available in the reaction medium. It can be observed that throughout the reaction, in shorter time and concentration it is not possible to achieve a balance, which leads to a constant interchange of predominant phase in the system. In the higher time and concentration experiments, a balance is virtually reached, in order that it cannot be observed separated diffraction peaks. However there is no significant increase of the structural ordering even for extreme times as 3 days of reaction. The ammonium chloride experiments showed that this reaction medium allows the formation of more crystalline phases than all others achieved in this research. However, it did not result in the diminished of the sodium consumption.
Acesso aberto (Open Access)
Desenvolvimento de processos de síntese de sodalita a partir de rejeitos de caulins da região Amazônica
(Universidade Federal do Pará, 2013-01-17) SILVA, Liliane Nogueira da; NEVES, Roberto de Freitas; http://lattes.cnpq.br/9559386620588673
In the study of the Sodalite synthesis used two wastes kaolins from two kaolin processing industries for paper coating, located in the Amazon region, operating in the region of Rio Capim (CRC) and Rio Jari (CRJ). Besides this, was also used as a source of silica and alumina to metakaolin, obtained by calcination of kaolin (MRC and MRJ, respectively). Preliminary chemical and mineralogical characterization of kaolin was performed to obtain information of its characteristics. The Sodalite synthesis was performed varying some parameters, such as starting material: kaolinite was used directly as starting material at temperatures of 80, 100, 120 and 150 °C, and, starting with metakaolinite at 95 °C. In order to observe the influence of ions OH, Cl- and CO32-, as well as Na2O/Al2O3 ratio, the syntheses were carried out varying the basic solutions, set temperature at 95 °C for the starting material MRC. Furthermore, the Na2O/Al2O3 ratio were maintained constant and temperature were varied in the reaction mixture to determine the ideal conditions for Sodalite synthesis. The starting materials and the synthesis products were identified and characterized by using XRay Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis, Thermal Methods (DTA/DTG) and Fourier Transform Infrared Spectrometry (FTIR). The method of synthesis that show best results were used as starting material metakaolin, with NaOH + Na2CO3 solution having Na2O/Al2O3 ratio of 3.89 conducted under stirring at 95 °C, atmospheric pressure and a time of 4 hours, for the two types of kaolin (CRC and CRJ). Using the MRC metakaolin, kaolin from the Rio Capim, under the above conditions was obtained by conversion of 86.5% by weight of sodalite and MRJ metakaolin, kaolin of the Rio Jari, the conversion was 73.6% in sodalite. All products were characterized as mesoporous materials, but starting from the product of metakaolin Rio Jari showed higher specific area.
Acesso aberto (Open Access)
Estudo de inclusões fluidas e química mineral do depósito aurífero do alvo Jerimum de Baixo, campo mineralizado do Cuiú-Cuiú, província aurífera do Tapajós, Pará
(Universidade Federal do Pará, 2018-03-06) OLIVEIRA, Helder Thadeu de; BORGES, Régis Munhoz Krás; http://lattes.cnpq.br/4220176741850416
The Jerimum de Baixo gold target is located in the Cuiú-Cuiú golfield, central region of the Tapajós Gold Province, Amazonian Craton. The target comprises monzogranitic rocks, essentially isotropic, that were weak to strongly hydrothermal and carriers of Fe-rich biotite. Chloritization, sericitization, sulfidation, silicification and carbonatization are the most important types of alteration. The produced chlorite is enriched in Fe of the chamosite type and was formed mainly between 280 and 315°C, whereas the white mica assumes muscovitic compositions. The mineralization is represented by quartz veinlets with low sulfide content (pyrite + pyrrhotite ± chalcopyrite ± galena ± sphalerite) in which gold occurs as free-milling particles and in more fragil and altered zones, usually associated with pyrrhotite. The petrographic and microtermometric study of fluid inclusions hosted in quartz veinlets defined aqueou-carbonic, carbonic and aqueous inclusions. The fluids with CO2 represent the probable mineralizing fluid and were generated by phase separation processes between 280 and 380°C, mainly. Further infiltration and mixing processes are indicated for the later aqueous fluids. Temperatures <400°C and the reduced character of the environment (pyrrhotite compounding the ore) point to H2S as the major ligand in the mineralizing fluid and Au (HS)-2 as the primary gold transporting complex. Phase separation, changes in pH conditions, and fluid/rock interaction were the important mechanisms for Au precipitation, which occurred at the brittle to locally brittle-ductile level of the crust (between 2 and 6 km). In general terms, Jerimum de Baixo presents similarities among the other deposits/targets previously studied in terms of hydrothermal alteration, fluid types and mineralization. The features observed in Jerimum de Baixo do not allow a classificatory framework absolutely adequate to any of the classical metalogenetic typological models. Characteristics such as type and style of hydrothermal alteration, type and low content of sulfides, types of fluids involved, estimated depth for mineralization, metallic association (e.g., S, Bi, Te), together with the good correspondence between the data collected in other deposits/targets in the Cuiú-Cuiú goldfield indicate for the Jerimum de Baixo target a gold deposit with magmatic-hydrothermal affiliation, presenting greater similarity to those deposits classified as belonging to Reduced Intrusion-Related Gold Systems (RIRGS).
Acesso aberto (Open Access)
Gênese das 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
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 gibbsitepreferably 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)
Geologia, mineralogia e afinidades petrológicas dos granitóides neoarqueanos da porção central do Domínio Canaã dos Carajás
(Universidade Federal do Pará, 2017-10-28) OLIVEIRA, Vinícius Eduardo Silva de; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The central portion of the Canaã dos Carajás domain, located in the northern part of the Carajás province was originally marked by the occurrence of undifferentiated rocks belonging to the Xingu complex and Plaque suite, as well as greenstone belts, mafic rocks of the Pium diopside-norite and high K calc-alkaline leucogranites (Boa Sorte and Cruzadão granites). A semi-detailed geological mapping (1:100.0000) was carried out in the Vila União area and allowed the identification of several deformed granite bodies intrusive in the Mesoarchean units. They correspond to the most expressive unit of the studied area and are composed predominantly of monzogranites with chemical and mineralogical affinity with the Neoarchean A-type granites of the Planalto and Vila Jussara suites. The variable felsic and ferromagnesian minerals contents, as well as the different proportions between them, allowed to distinguish four major groups of granitoids: (i) biotite-hornblende monzogranites (BtHblMzG); (ii) biotite granites and leucogranites (BtLG); (iii) biotite-hornblende tonalites (BtHblTn); and quartz diorites (QD). The tectonic foliation of these rocks follows the regional E-W trend and exhibits high angles (70-85°). Well-developed core and mantle structures in quartz and feldspar crystals, as well as the presence of serrated and irregular contacts between these crystals suggest that dynamic recrystallization occurred at relatively high temperatures (> 500 °C). These rocks exhibit a wide variation in silica content (61.7 – 75.91 wt%), are metaluminous to slightly peraluminous and show affinity with A-type (high HFSE) and ferroan granites. Based on magnetic petrology studies it was possible to distinguish two groups of rocks: (1) granites containing only ilmenite with low magnetic susceptibility values (MS; <0.570 × 10-3 SI), and (2) granites with magnetite as the main iron and titanium oxide mineral and higher MS values (> 1.437 × 10-3 SI). Textural and compositional evidences indicate that magnetite and ilmenite are earlycrystallized phases and titanite has magmatic origin. Amphiboles are calcic and classified as hastingsite, whereas biotites are rich in the annite molecule. The relatively high Fe/(Fe + Mg) ratios found in the amphiboles of the BtHblMzG and BtHblTn varieties indicate that these granitoids were formed under low to moderate fO2 conditions, whereas in the BtLG the lower values of this ratio suggest more oxidizing conditions. Geothermometers point to crystallization temperatures between 830 – 930 °C in the different facies. The high total Al content in the amphibole crystals suggests crystallization at pressures between 400 and 800 MPa, indicating that these granitoids were emplaced at different crustal depths.
Acesso aberto (Open Access)
Mapeamento geoquímico e estimativa de Background em solos na região da Província Mineral de Carajás – Leste do Cráton Amazônico, Brasil
(Universidade Federal do Pará, 2018-03-09) SALOMÃO, Gabriel Negreiros; DALL’AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
This research is linked to the project 'Geochemical Background of the Itacaiúnas River Basin' under development by the Vale Institute of Technology Sustainable Development (ITVDS). In Brazil, geochemical surveys have been carried out mainly by the Companhia de Pesquisa de Recursos Minerais (CPRM – Brazilian geological survey), which has executed some projects focused on the region of Carajás, the largest mineral province in Brazil and in which the Itacaiúnas River basin is located. One of these projects, titled 'Evaluation of the Potential of the Strategic Mineral Resources of Brazil', carried out in the year 2012, covered the region of Canaã dos Carajás and generated a large collection of soil geochemical data. As such data were made available, the main purpose of this dissertation is to explore as much information as possible to elaborate multi-elemental geochemical maps based on interpolation techniques and to establish geochemical background values of the elements in soils of the target region of the CPRM survey. 225 soil samples, along with 32 duplicates, were collected in that project in an area of approximately 4,500 km2. The 80 mesh (0.177 mm) fraction of these samples was submitted to aqua regia digestion and 53 elements (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Pd, Pt, Rb, Re, S, Sb, Sc, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn, Zr) were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) for the major and minor elements and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for the trace elements. The analytical data provided by the CPRM were initially submitted to a quality control by means of Residual Standard Deviation (RSD) calculation for each duplicate. Then, the simple substitution method was used for the values beyond the limit of detection, followed by uniand multivariate statistical analyzis, including descriptive statistical treatments, identification of outliers via Grubb test, normality tests (Lilliefors and Kolmogrov- Smirnov), correlation and cluster analysis. All statistical analyzis previously highlighted were conducted by STATISTICA® and SPSS® softwares. To determine the values of threshold and geochemical background and graphical representation were used the methods boxplot and cumulative frequency curve methods (Minitab® and Excel® software) and the iterative techniques 2 and calculated distribution function (freeware Visual Basic macro denominada VB Background®). For the construction of geochemical maps, the World Geodetic System 1984 (WGS84) coordinate system was adopted as standard. Spatial representations followed techniques of interpolation according to the kriging or inverse distance weighting (IDW) methods. 43 analyzed elements were submitted to the statistical tests, having been left aside Au, B, Ge, Na, Pd, Pt, Re, Se, Ta e Te, because they presented ≥90% of the analytical data below the limit of detection. Correlation analyzis revealed 14 moderate correlations (0.650> r ≥ 0.575) and 19 high correlations (r ≥ 0.650), generally consistent with usual geochemical associations in geological environments such as Cr-Ni, Cu-Ni and U-Th. The cluster analysis discriminated seven clusters, at a linkage distance of 0.8, with evident geogenic origin, as for example the group composed of Cr, Ni and Mg, typical of mafic-ultramafic rocks. The geochemical maps allowed to identify occurrences of several anomalies in soils, interpreted as being of geogenic origin. Thus, U, Th, La and Ce enrichment was found in soils derived from sub-alkaline neoarchean granites, for example Estrela, Serra do Rabo and Planalto granites, and Cr and Ni in soils from mafic-ultramafic rocks of Luanga and Vermelho complexes and the Cateté Suite. Elements typically associated with anthropic activities, such as P, Zn, Mn, Ba and Pb, as well as potentially toxic elements (EPT), such as Al, As, Bi, Cd, Co, Hg, Mo and Sn, did not generally exhibit, anomalous concentrations and, when this occurred, these appear to be due to geological conditions. Among the methods used to estimate the background values of the 43 evaluated elements, the iterative technique 2 was the one that presented the best result. In cases where this method could not be used, the values obtained by the calculated distribution function (As) and the boxplot representation (Hg and S) were adopted as background. The cumulative frequency curve showed to be a useful graphical technique in the identification of outliers and multiple thresholds. The 225 samples were grouped into five classes that revealed the close linkage between the background values and the geology of the region: 1) Sub-alkaline granites (39 samples); 2) Sedimentary and metasedimentary rocks (28 samples); 3) Gneisses and associated granitoids (70 samples); 4) Metamafic, intermediate and banded iron formation (BIF) (80 samples); 5) mafic-ultramafic rocks (8 samples). With the results obtained, it is concluded that, in the scale of the survey carried out, there is no conclusive evidence of contamination related to human activity, but rather strong evidence of a marked geogenic contribution in the soils of the study area.
Acesso aberto (Open Access)
Micromorfologia, mineralogia e geoquímica da bauxita nodular de Trombetas – PA
(Universidade Federal do Pará, 2018-10-18) LIMA, José Diogo de Oliveira; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Brazil's main bauxite deposits are concentrated in the Amazon region, specifically in the state of Pará. The three main mines are located in Trombetas, Paragominas and Juruti, and they’re responsible for 85% of Brazil's bauxite production. Even with the favorable mineral scenario in Brazil and especially in the state of Pará, there are already companies that are currently competitive in the current market, they are seeking to develop studies of the characterization and use of nodular bauxite in this type of deposit. The ore, so far, is considered as marginal, it means low-grade ore in the mineral industry. In this context, this work sought to evaluate Trombetas deposits’ nodular bauxite from their texture, mineralogical and chemical characteristics as a possible aluminum ore. In the field, seven lithographic profiles were described on the mining fronts of Bela Cruz and Monte Branco mines belonging to ‘Mineração Rio do Norte’. Then, 19 samples were collected, which were described, photographed and prepared for mineralogical and chemical analyzes. The mineralogical phases were identified by X-ray Diffraction (XRD) and Scanning Electron Microscopy coupled to the Dispersive Energy System (SEM/EDS). The textural aspects involved optical microscopy and Scanning Electron Microscopy coupled to the Dispersive Energy System (SEM/EDS). The chemical analyzes were performed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), Inductively Coupled Plasma Mass Spectrometer (ICP-MS), X-ray Fluorescence (XRF), titulometry and gravimetry. The profiles investigated comprise from the base to the top the bauxite horizon (HBX) which is represented by gibbsite concretions surrounded by a clay matrix. The overlapped bauxite nodular horizon subdivided into HBNB, HBNI and HBNT, is formed by gibbsitic nodules, of fine texture, that impresses solid and porcelanate aspect and they are surrounded by a clayey matrix. The clay cover (CAR) at the top is formed by a yellow clay, corresponding to Belterra Clay. In the profiles, the fragments > 0.500 and ~0.500 mm of the HBX and HBNB, HBNI and HBNT are essentially composed of gibbsite associated with kaolinite, hematite and anatase. The dominance of gibbsite in the fragments > 0.500 and ~ 0.500 mm of the HBNB, HBNI and HBNT, presents a potential of nodular bauxite as a possible aluminum ore. However the fragments < 0.500 mm, clayey matrix of HBX and HBNB, HBNI, HBNT and CAR are mainly composed of kaolinite associated with gibbsite, hematite, quartz and anatase. The kaolinite domain in the HBNB, HBNI, HBNT fragments < 0.500 mm, makes it difficult to consider them as possible aluminum ore. As for the heavy minerals (zircon, rutile and tourmaline), no contrast was found between the horizons and the clayey cover. The chemical composition consists essentially of SiO2, Al2O3, Fe2O3 and TiO2, which reinforce the main minerals identified and as these the contents differ according to the horizons. The concentrations of the trace elements are variable, V, Cr, Ga, Se, Zr, Nb, Mo, Sn, Hf, Ta, W, Hg, Bi, Th and U are above the crustal average in all fragments, clayey matrix of HBX, HBNB, HBNT and CAR. Trace elements such as V, Cr, Ga, Mo, Hg and Bi correlate positively with Fe2O3 (hematite and goethite). While Nb, Sn, Hf, Ta, Th, U, correlate positively with zirconium (zircon) and titanium (anatase). When normalized to the chondrites, the distribution curves present parallelism between the various fragments, clayey matrix of HBX, HBNB, HBNT and CAR, with curves that exhibit Eu anomaly, as well as an enrichment of the heavy rare earth elements (HREE) in front of the light rare earths elements (LREE). The data obtained in the investigated profiles of Bela Cruz and Monte Branco mines demonstrate broad similarity to Belterra clay-type nodular lateritic-bauxite profiles found in Amazon, where the clayey matrix of the nodules resembles textural, chemical (larger elements and traces) and mineralogical (including heavy minerals) with this covering clay.
Acesso aberto (Open Access)
Minerais de manganês como contaminantes do minério de ferro na mina N5W em Carajás, Pará
(Universidade Federal do Pará, 2015-09-29) COSTA, Luiz Claudio Gonçalves da; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Mineralogical characterization and control of manganese and silica contents in the Carajás mine iron ore is a routine task. Relatively high concentrations of manganese and silica minerals, considered ore impurities, are present in the high grade iron ore (>65% Fe) of the N5W mine. This study aimed to identify these minerals and their mode of occurrence in the iron ore from N5W, improving the mine planning and exploitation. The main manganese minerals in the iron ore are: (a) pyrolusite, bixbyite, cryptomelane, hollandite, ramsdellite and chalcophanite, all Mn oxy-hydroxides; and (b) the braunite, a silicate. These minerals were found in hydrothermal veins and veinlets, cross-cutting the primary bedding of the iron ore and subordinately forming centimetre scale lens shaped veins, interbedded in the jaspilite layers. The Mn rich veins are spatially associated with fault zones and breccia bodies showing pyrolusite, chalcophanite, braunite and bixbyite veins, subordinated lenses of cryptomelane and hollandite. The presence of pyrolusite and cryptomelane indicates weathering of the rocks. Quartz and Fe-Mn oxy-hydroxides are the main minerals filling faults and fractures in the N5W mine, where MnO grades in veins, reach up to 61,74%. The Mn minerals in the iron ore are indicative of sedimentary and hydrothermal origin. Weathering caused alteration of the primary minerals, promoting mobilization and reprecipitation of new Mn minerals together with Fe oxy-hydroxides. Typical geochemical association in the Mn rich iron ore Mn-As-Cu-Zn-Ag with positive anomalous ETR levels, whilst in the iron formation Zr-Hf-Nb-Ta-Sc-Th with ETR negative values. The rare earth elements concentrations are higher in the Mn rich zones. These zones show strong positive Ce anomalies when hollandite is present. Higher SiO2 contents are related to the presence of metric jaspilite boulders surrounded by hematite friable, in the thick saprolite zone. Finally, the Mn contaminants are diverse in origin, however hydrothermal Mn rich minerals are dominant, closely associated with the proto-iron ore. The high SiO2 contents are indicative of the base of the alteration profile, incorporating part of the proto-ores. Keywords: Mn Oxi-hydroxides; hematite; quartz; silica; contaminants, Carajás Formation.
Acesso aberto (Open Access)
Mineralogia e geoquímica dos perfis bauxíticos da mina Miltônia 3, região de Paragominas/PA
(Universidade Federal do Pará, 2015-10-16) PEREIRA, Carla Braga; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The Paragominas Bauxite Province is located in eastern of Pará state and western of Maranhão state, occupying the NW portion of Grajaú Basin and the southern of Bragantina platform, with an area of approximately 50.000 km2. The important bauxite deposites from that area were originated by an intense chemistry weathering above siliciclastic rocks from Cretaceous age. This research focus on the mineralogical e geochemistry studies of bauxite profiles in the area of Bauxite mine that belongs to the Norsk Hydro Company, in Miltonia 3 mine, municipality of Paragominas, Pará state. This research aims to contribute to understanding of the origin and developing of these profiles. Were conducted two sample collections of lateritic profiles representatives of Miltonia 3 mine, following the chemistry, mineralogy and texture differences of the horizons that structures the studied profiles. We used the following methodological procedures and/or instrumental techniques: X-rays Diffraction (XRD), Scanning Electron Microscopy (SEM), petrology and chemical analysis. The lateritic profiles studied in this research were described according to their horizons structuring: Amorphous Bauxite (AB), Crystallized Amorphous Bauxite (CAB), Crystallized Bauxite (CB), Ferruginous Laterite (FL). In the profile 1, the overlying horizon to FL is described as Nodular Bauxite (NB), while in the profile 2, it is the Crystallized Nodular Bauxite (BNC). Both of these profiles are covered by unconsolidated sandy-clay horizon, with an orange red coloring, called by many authors as Belterra clay. Petrographically, the horizons show the following typical mineral of a bauxitic/lateritic profile: gibbsite, kaolinite, goethite, hematite e anatase. This paragenesis was confirmed by XRD analysis, which the mineral content varies for each horizon. Allied to the SEM analysis it is possible to describe the morphologic aspect of gibbsite and kaolinite crystals. It is noticeable the presence of three gibbsite generations, which the precocious phase is part of matrix, sometimes, associated with iron oxide-hydroxide, showing a cryptocrystalline character. The second generation comprises microcrystalline crystals that fill partially or totally pores. The latest generation is cryptocrystalline crystal found occupying totally or covering the cavity walls of cutans. The geochemical pattern of Al2O3, Fe2O3, SiO2 and TiO2 residual phases are similar in both profiles, as well as the contents of Al2O3_available e SiO2_reactive. Over the profile, the contents of SiO2 e SiO2_reactive are more expressive in the most clayey layers, and they reflect the kaolinite content. The content of Al2O3_available has the same Al2O3 behavior due to: the first is related to gibbsite, the most elevated contents are in top of AB, CAB e CB, and the last represents the most economically exploitable level. According to the order/disorder degree of this kaolinite in the soil profile, it was verified an elevation of the FWHM (Full Width at Half Maximum) results from base towards top, that showed the possibilities of: 1) kaolinite degradation with the process of developing of lateritic profile; and/or neoformations of new kaolinite generations with low crystallinity. The new data furnished during the analysis give support to understand the process that produced the mineralogical, chemistry and textural differences and similarities that exist between bauxite horizons, as well as the recovery of bauxitization process (two phases of bauxitization) that resulted in formation of Nodular Bauxite (NB) and Crystallized Nodular Bauxite horizons, leading the hypothesis of polyphasic and complex evolution of studied profile, wich culminated in the origin of bauxitic/lateritic deposits.
Acesso aberto (Open Access)
Mineralogia e petrologia do complexo ultramáfico e alcalino de Santa Fé - GO
(Universidade Federal do Pará, 1978) SOUSA, Ana Maria Soares de; GIRARDI, Vicente Antonio Vitório; http://lattes.cnpq.br/6876269679513816
Acesso aberto (Open Access)
Mineralogia, geoquímica e minerais pesados do perfil laterito-bauxítico com cobertura e sua relação com o grupo Itapecuru: lavra piloto ciríaco (Rondon do Pará)
(Universidade Federal do Pará, 2015-07-11) PANTOJA, Heliana Mendes; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The lateritic-bauxite profile studied in Rondon do Pará is part of the Paragominas Bauxite Province, the most important of the Brazil that hosts world-class deposits of considerable economic value. The deposit comprises six horizons: bauxitic clay at the bottom, massive bauxite, massive iron-aluminous crust, iron-aluminous crust dismantled, ferruginous spheroliths and a clay cover equivalent to the "argilas de Belterra" at the top. The sedimentary rocks of the Itapecuru Group are the probable source of the lateritic-bauxite profile and include weathered siltstone and claystone. The mineralogical composition of the three studied units (Itapecuru Group rocks, lateritic-bauxite profile and clay cover) is similar and consist to kaolinite, quartz, hematite, goethite and gibbsite, accessory minerals include anatase and heavy minerals (zircon, tourmaline, rutile, staurolite and opaque). The units differ mainly in this content variation and the absence of gibbsite and goethite in the rocks of Itapecuru Group. The chemical composition of the three units shows that Al2O3, SiO2, Fe2O3, TiO2 and LOI are the most abundant constituents, related to the major minerals. Trace elements content in the three units are heterogeneous with V, Cr, Ga, Zr, Hf and Th showing concentrations above the crustal average, these elements display good correlation with iron oxy-hydroxides. When normalized to chondrites, the three units differ by positive Ce anomaly in the Itapecuru Group rocks, but are similar in negative Eu anomaly, the depletion of LREE and enrichment of HREE. The data obtained show clear affinities between the three units, suggesting that the sediments of the Itapecuru Group are similar to those of the bedrock of lateritic-bauxite profile while their respective cover demonstrates strong relationship with the crusts and spheroliths. The structure of the lateritic-bauxite profile together with mineralogical and chemical data allow to correlate the Rondon do Pará lateritic-bauxite profile with the deposits of Paragominas and Juruti.
Acesso aberto (Open Access)
Opalas gemológicas do Piauí: gênese revelada por microtermometria e minerais associados
(Universidade Federal do Pará, 2014-04-25) MARQUES, Gisele Tavares; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Opals from Pedro II and Buriti dos Montes, in the Piauí State, are the most important occurrences of this gemstone in Brazil, both in terms of volume and -gemological quality that is comparable to the famous Australian opals. However, informality in the extraction and marketing of these opals, as well as the lack of information about the genesis of these deposits do not permit prospecting for new deposits, and the establishment of a certificate of origin for Piauí opals, would allow their formal participation in the international gemological market. Some authors have been studied these opals, revealing strong evidences of their hydrothermal origin, but until now, no work discussed the physico-chemical characteristics of the fluids that would have originated these opals deposits. Thus, the main objective of this work was to understand the hydrothermal system responsible for the genesis of opals from Piauí, i.e., to characterize the fluids that originated the mineralization and show its relationship with the geological context of this region. Pedro II and Buriti dos Montes counties are located in the northeastern portion of the Piauí State, at approximately 230 km east of the capital Teresina. The opal occurrences are on the basis of the Parnaíba Basin, constituting veins and veinlets in the sandstones of the Serra Grande (Buriti dos Montes) and Canindé (Pedro II) groups, which are cut by diabase sills and dikes of the Sardinha Formation. They also occur in cementing breccias and as colluvial and paleochannel deposits. Associated to opals, locally there are veins of quartz, chalcedony, barite and hematite (or goethite). In general, opals from Pedro II present play-of-color, are mostly white or bluish with a milky appearance, semitranslucent to opaque, and have solid inclusions little bit apparent. In contrast, orange opals from Buriti dos Montes do not show play-of-color, their color ranges from light yellow to brownish red, they are semitransparent to translucent, and contain a large variety of solid inclusions. The obtained data reveal that the opals from Pedro II are typically of amorphous type (opal-A), while the opals from Buriti dos Montes range between amorphous and cristobalite-tridymite (opal-CT). In the precious opals, the typical play-of-color is caused by the regular arrangement of the silica spheres that constitute them. The absence of opaline cement among the spheres reinforces the beauty of this effect. On the other hand, the orange opals do not show play-of-color, but they have greater transparency due to the small size of the spheres. The solid inclusions also produce beautiful effects in the studied opals, mainly in the orange variety that is more transparent. Besides this, the solid inclusions set reveals intrinsic characteristics to hydrothermal processes that originated the studied opals. Botryoidal, dendritic and nodular aggregates are examples of inclusions formed by fragments of the host sandstones, which were carried by the hydrothermal fluids that generated the opals. In the opals from Buriti dos Montes, the red, orange and yellow hues are produced by the partial dissolution of the Fe oxy-hydroxides inclusions. Similarly, the green color in the precious opals is related to Co-pentlandite microcrystals included in them. The set of minerals associated to opals leads to a mineralogical-geochemical signature marked by high contents of Fe and Al in opals with hematite/goethite and kaolinite inclusions, such as the considerable increase in the rare earth elements contents, in the opals that have kaolinite and apatite inclusions. Among the trace elements, Ba is the most abundant, and it probably was incorporated to hydrothermal fluid, considering that veins of barite are frequently found in this region of Parnaíba Basin. Some features such as flow structures in the opals, corrosion and partial dissolution in the hyaline quartz crystals and mineralogical inclusions, hydrothermal quartz veinlets that overgrew to detrital grains, and zoning in the quartz crystals, confirm that these opals have hydrothermal origin. The Gondwana rupture would have caused a wide fissural basic magmatism, which was the responsible for the heat supply that generated the first convective cells of hot fluids. The water contained in the sandstones certainly filled the system and enriched in silica through partial or total dissolution of the quartz grains of sandstones. This hydrothermal fluid was subsequently hosted and cooled in the fracture systems, precipitating the opal and associated minerals.
Acesso aberto (Open Access)
Organofilização de uma Mg-bentonita da bacia do Parnaíba-Sul do Maranhão e sua utilização em poli (metacrilato de metila)
(Universidade Federal do Pará, 2014-02-21) CAVALCANTE, Manoella da Silva; http://lattes.cnpq.br/7249500407405478; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
Bentonites are clays whose main constituent is a clay mineral of the smectite group, mainly montmorillonite. According to the predominant cation that occupies the interlayer space of the smectite, they can be classified as sodium-, calcium- or magnesian-bentonites. Such clays have wide industrial applications, such as: drilling fluids, pelletizing, foundry molds, among others. For some specific applications that add greater value to the final product, as in the synthesis of polymer/clay nanocomposites, it is necessary to intercalate organic ions in the interlayer of the clay mineral. In Brazil, industrial production of organoclays is small and geared towards the markets of paints, greases and polyester resins. Most companies that exploit bentonites for the traditional uses and do not produce this type of material are showing increasing interest in this new kind of application. In this context, this study aimed to evaluate the potential of the Formosa Bentonite in the production of organoclays and its application in the synthesis of polymer/clay nanocomposites. Formosa is a Mg-bentonite recently described and relatively abundant in northeastern Brazil. For this purpose, synthesis experiments were carried out by varying the concentration of two surfactants: hexadecyltrimethylammonium ions (HDTMA+) and dodecyltrimethylammonium (DTMA+), in the concentrations 0.7, 1.0 and 1.5 times the value of CEC, with reaction time of 12 hours and temperature variation of 25 ºC and 80 ºC. The Mg-bentonite was used as starting material both in natura and activated with sodium carbonate. Both the starting material and the organoclays obtained were characterized by XRD, DTA/TG and FTIR. The clays that exhibited better intercalation results were used in the proportions of 1%, 3% and 10% for further synthesis of the polymer (PMMA)/clay nanocomposites. The XRD results confirmed the intercalation of organic ions in the interlayer space of the Mg-smectite, for both in natura and activated samples. According to FTIR results, it was observed that the ratio of gauche/trans conformers decreases with the increasing of basal spacing. The results of DTA/TG confirm the thermal stability of organoclays at a maximum temperature of 200 °C, allowing the use of such material in the synthesis of polymer/clay nanocomposites obtained by the fusion process. XRD patterns confirmed the intercalation of PMMA in the interlayer space of the Mgsmectite for all nanocomposites produced. With the DSC analysis, it was possible to observe the increase in glass transition temperature for all nanocomposites in comparison with pure PMMA. Thus, it is possible to conclude that the Mg-bentonite can be intercalated with alkylammonium ions, without previous sodium activation, forming organoclays, as well as their use in the synthesis of nanocomposites. This possibility of using natural (non-activated) Mg-bentonite may represent an important difference in terms of process costs, in comparison with existing Ca-bentonites in Brazil, or even the imported, that need to be activated during beneficiation. Finally, one believes that the research should proceed with the evaluation of mechanical properties of the nanocomposites produced in this work, aiming future possibilities of application for such materials.
Acesso aberto (Open Access)
Pesquisas mineralógicas e geoquímicas para a distinção de basaltos intrusivos e extrusivos no Vogelsberg Alemanha Federal
(Universidade Federal do Pará, 1977-07) OLIVEIRA, Elson Paiva de; SCHWAB, Roland Gottlieb
In a drill hole of 450m made in the central part of the volcanic complex Vogelsberg, West Germany many authors found an alternating sequence of alkali olivinbasalts and tholeiites, consisting of 7 series with a total of 293m. Radiometric age dating suggests that two of the alkali olivinbasalts are intrusive. One of them, serie 3, however shows traces of weathering on its surface. The present study includes chemical analyses of major and trace elements (Ni, Co, Cu, Zn, Li and Be) as well as mineralogical investigation by means of X-ray diffraction and optial methods. The objective of these analyses was the chemical and mineralogical characterization of the weathering horizons and of the possible effects of differentiation in the units considered intrusive. The commom association of haematite, montmorillonite and quartz fragments in the weathered horizons, as well as the increase of Ni, Co, Cu, H2O and Fe2O3 and the decrease of Li, Be, FeO, MgO and CaO from the bottom to the top of one of the "intrusive units" in serie 3, shows that this unit was exposed to the earth's surface and therefore cannot be considered intrusive. The other alkali olivinbasalt in serie 5 shows incipient gravitative differentiation effects but witho ut significant textural variations. On the other hand there is amigdaloidal texture on its top suggesting also an extrusive nature.
Acesso aberto (Open Access)
Quartzo magmático e hidrotermal do depósito de ouro São Jorge, província aurífera do Tapajós-PA: petrografia, MEV-CL e implicações metalogenéticas
(Universidade Federal do Pará, 2015-08-05) SOTERO, Aldemir de Melo; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
The São Jorge Deposit (DSJ), located in the municipality of Vila Riozinho, Gold Tapajós Province, southwest of Pará state, is hosted on 1.89 Ga monzogranite rocks, hydrothermalized at different intensities, belonging to the Younger São Jorge granite. Four morphologicaltextural types of quartz (Qz1, Qz2, Qz3 e Qz4) were identified through images of scanning electron microscopy-cathodoluminescence (SEM-CL) in the mineral assemblages proposed by Borges et al. (2009) to the area of the São Jorge gold deposit. In the most preserved rocks (assemblages 1 and 2), rich in amphibole and biotite, occur anhedral crystals of primary magmatic quartz, with moderate to high luminescence (Qz1). In the altered rocks (assemblages 2 and 3), post-magmatic to hydrothermal fluids affected the granite and percolated fractures in Qz1 and crystallized Qz2 not luminescent (dark). In the most intensely altered rocks (assemblage 4), successive alteration, dissolution and recrystallization processes gave rise to zoned subhedral (Qz3) and euhedral (Qz4) quartz crystals, typically hydrothermal, the latter being host of the gold mineralization. The textural evolution of quartz is directly related to hydrothermal fluids that affected the rocks of the Younger São Jorge granite. Backscattered electrons images (ERE) and semiquantitative analysis by energy dispersive spectroscopy (EDS) identified two generations of gold: Au1, enriched in Ag (4.3 to 23.7%) and included or associated to crystals of Py; Au2, enriched in Te (1.1 to 17.2%) and included in Qz4. The study of quartz crystals by SEM-CL provided important morphological and textural information for understanding of the hydrothermal processes that acted in the mineralized area of the São Jorge gold deposit, allowing the application of this methodology in studies of quartz of other hydrothermal deposits.
Acesso aberto (Open Access)
Síntese de pigmentos zeolíticos a partir de zeólita A derivada de rejeito de caulim da Amazônia
(Universidade Federal do Pará, 2013-03-13) MENEZES, Raquel Aranha de; PERGHER, Sibele Berenice Castellã; http://lattes.cnpq.br/5249001430287414; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
Ultramarine pigments were successful synthesized from zeolite A obtained from kaolin waste. This waste has been used as an excellent source of silicon and aluminum for zeolite synthesis because of its high kaolinite concentrations and low contents of other accessory minerals. The cost is naturally less than the industrialized product. The zeolite NaA derived from kaolin waste presents characteristics favorable for synthesis ultramarine pigments, sulfur species can be inserted inside the zeolite voids, which act as chromophores, and should provide some protection against oxidation and avoids high levels of toxic gases during reaction. Zeolite A was mixed with Sulfur and Sodium Carbonate in different proportions in order to check the influence of this variation in color and shade of pigments. Further calcined for 5 hs@500º C. They were characterized by XRD, XRF and, Raman in addition to visual classification by color and shade. These products show colors from blue to green at different shades, both influenced by the amount of additives, cooling rate after calcination and by particle size. Thus, a different quantity of the same additives in the same zeolitic matrix provides an increase in the color intensity, cooling rate after calcination and particle size induces the color change. X-ray diffraction patterns showed that the structure of zeolite NaA is not change in sodalite type as normally found in the literature. Raman spectroscopy identified sulfur species responsible for color in zeolitic pigments. S6 2- is yellow and S3- is blue and the mixture both is green, majority color in this work. Utilization the kaolin waste in the production of zeolitic pigments is a good proposal for sustainable production.

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