Navegando por Assunto "Bauxita - Rondon do Pará (PA)"

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Acesso aberto (Open Access)
Argila de Belterra das coberturas de bauxitas da Amazônia como matéria-prima para a produção de cerâmica vermelha
(Universidade Federal do Pará, 2018-01-10) BARRETO, Igor Alexandre Rocha; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The Amazon region holds the largest reserves of bauxite in Brazil, whose deposits are covered by a thick bundle of clay material, known as Belterra Clay (ABT). The wide distribution, superficial occurrence, therefore accessible, and clayey ABT nature have aroused the interest of this work in evaluating its technical viability for the production of red ceramics. For the present study, ABT was selected from the large bauxite deposits of Rondon do Pará, samples of the yellow soils from Mosqueiro, illitic clay and gibbsitic clays and one sample of the clayey siltstone. This clay and other materials used as additives were characterized by X-ray Diffraction (XRD), X-Ray Fluorescence (FRX) (CT), Spectrometric Thermal Analysis (TG), Differential Scanning Calorimete (DSC), Inductively Coupled Plasma Spectrometry (ICP-MS), Coupled Plasma Optical Emission Spectrometry (ICP-OES), Scanning Electron Microscopy (SEM) Laser Particle (APL). To determine the physical and mechanical properties, were produce specimens through different mixtures with the samples of Belterra clay and percentages (20, 30 and 40%) of the yellow soil, clayey siltstone, gibbsitic clays and illitic clay. The specimens were calcined at three different temperature moments (900, 1000 and 1200 ° C). Then, linear retraction, water absorption, apparent porosity, apparent density and bending rupture tension were measured. ABT is essentially kaolinite, having quartz, goethite, anatase and gibbsite as accessory minerals. The pure and simple ABT did not present favorable technological aspects for the production of ceramic products, however the same with addition of the yellow soil and clayey silt from the same region significantly improved the technological characteristics of the ABT.
Acesso aberto (Open Access)
Geologia, mineralogia e geoquímica do perfil lateritobauxítico da lavra piloto Décio (Rondon do Pará)
(Universidade Federal do Pará, 2017-03-24) SANTOS, Pabllo Henrique Costa dos; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
During the Eocene-Oligocene, extensive lateritic coverings were formed in the Amazon. In this context, the sedimentary sequences of the Parnaíba and the Amazon Basins were lateritized and generated four world-class bauxite deposits: Juruti, Trombetas, Paragominas and Rondon do Pará. The latter is the new bauxite exploration frontier of the Amazon and the Décio pilot mine was developed in it, which presents a 3 m thick laterite-bauxite profile, which extends laterally through vast plateaus with about 350 m of altitude. This work sought to deepen the study of bauxite and its relationships with lateritic landscape in the Amazon region. In the field, five lithological profiles were described in the Décio pilot mine. Then, 42 samples were collected for laboratory analysis involving mineralogical characterization (X-ray diffraction); textural (Optical Microscopy and Scanning Electronics); and chemical (Optical Emission Spectrometry and Mass Spectrometry with Inductively Coupled Plasma). The most probable precursor rocks are the clay facies of the Itapecuru Formation. These would have evolved to a bauxitic clay horizon and then to massive microcrystalline and microporous red bauxite. Bauxite, on the other hand, converges to spherolytic iron-rich crust, rich in iron oxide and partially dismantled. This set is covered by a horizon of ferroaluminous spherolites and a nodular bauxite horizon. The whole set is covered by unconsolidated yellow to red clay, equivalent to the Belterra Clay. The minerals that resisted laterite weathering were zircon, tourmaline, rutile, kyanite and quartz. The neoformed were hematite, goethite, gibbsite, part of the kaolinite, besides the anatase. The main chemical constituents are Al2O3, Fe2O3, SiO2 and TiO2, which together make up more than 99.5% of the profile. Its distribution suggests that the lateritic evolution developed in situ occurred until the formation of the spherolithic horizon. The TiO2 content is much higher in the bauxitic clay horizon than in the other overlying horizons, which is not common in a lateritic evolution from a single, homogeneous parent rock. In addition, Zr and ETR decrease towards the top of the profile, which would also not be expected. Therefore, although the precursor rocks of the entire profile were sedimentary, there was a compositional contrast between those that generated the bauxitic clay horizon and those that generated the other horizons. In addition, the pattern distribution of trace elements shows that even starting from slightly differentiated parent rocks, almost the entire profile followed a similar pattern of evolution, with the exception of the nodular bauxite horizon that behaves as separate unit. These characteristics differ the lateritic profile of the Décio and Ciríaco pilot mine, located in the same bauxite region, but formed from more homogeneous parent rocks.
Acesso aberto (Open Access)
Química, micromorfologia e refinamento por Rietveld das fases minerais da Argila de Belterra em Rondon do Pará
(Universidade Federal do Pará, 2017-02-20) NEGRÃO, Leonardo Boiadeiro Ayres; PÖLLMANN, Herbert; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Bauxite deposits in the Amazon region are commonly covered by yellowish or reddish clays that can reach up to 25m thick, known as Belterra Clay (BC), term attributed after Sombroek in 1966 describe similar clays, but not related to bauxites in the region of Belterra, Lower Amazon. In Rondon do Pará, the BC has between 10 and 13 m thick, covering world-class bauxite reserves. Representative samples of BC from three pilot bauxite mines (Branco, Décio and Ciríaco) in Rondon do Pará were studied. The BC covers laterite-bauxite regoliths with well-defined horizons. From the basis to the top, they are composed of: bauxite clay, followed by massive bauxite, massive iron-aluminous crust, dismantled iron-aluminous crust, ferruginous spherolites, and a horizon with bauxite nodules in a clayey matrix. In discordant contact with the lateritic profile, the BC has reddish brown colors at the base, with yellowish tones towards the top. It has a homogeneous appearance with no visible sedimentary structures, silt-clayey aspect and with fragments of porcelain bauxite (popcorn like) at its base. The mineral composition of the material is dominated by kaolinite, with Al-goethite, gibbsite, hematite, anatase and residual quartz. The SiO2/Al2O3 ratio of about 1.050 is lower than the theoretical kaolinite (1.178), confirming the existence of gibbsite and even Algoethite as aluminum carrier. As observed by X-ray diffraction analysis, kaolinite is of low structural order, evidenced by the low distinction of the diffraction bands at the 19-22° 2ϴ (Cu anode) region and because this mineral has no satisfactory correlation with any structural model of kaolinite, which was considered the principal difficulty in the application of the Rietveld method. Al-goethite has about 32 mol% of Al and is responsible for the ocher / yellowish color of the BC. This mineral associated with hematite and amorphous iron hydroxide (up to 0.5% Fe) is responsible for up to 13% of Fe2O3 contents. Quartz rarely exceeds 1% as fragments in the clayey matrix. Anatase has concentrations between 2.4 and 2.8%. As observed by SEM, with the exception of quartz, the minerals represent pseudohexagonal crystals measuring from 150 to 700 nm. The thermal behavior of the material confirms its mineralogical composition. Its mineral quantification by thermogravimetric analyzes is in accordance with the Rietveld method and stoichiometric (FRX) results, despite a precise correlation between these methods was unfeasible.