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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Item Acesso aberto (Open Access) Aspectos lito-estruturais das minas de ferro N4E e manganês do azul, Serra dos Carajás-Pará(Universidade Federal do Pará, 1991-08-06) MARÇAL, Mônica dos Santos; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286The areas of iron (N4E) and manganese (Azul) mines in the Serra dos Carajás region were investigated with emphasis on structural geology, aiming to define the geometric arrangement of the various ore bodies and the kinematic framework, as well as their relationships with the regional structuring. The iron mine (N4E) is subdivided into two segments called Aba Leste and Aba Sul. The lithotypes occurring in this area are represented by friable itabitite (soft hematite HM, hard hematite HD), metajaspilite, metavolcanic rocks and canga. . Most of the rock units are distributed in the form of lenses and discontinuous and wedged bands, with a general orientation N-S on the East Rim and E-W on the South Rim, drawing a “J” with concavity facing northwest. The analysis of the structural elements present in the rocks of the N4E mine, in line with the information available for the Serra Norte region, allowed the characterization of three sets of main structures: the oldest set comprises the mylonitic foliation, the shear zones with oblique riding character, stretch lineation and associated folds; the second set refers to the NW-SE, E-W and N-S ductile transcurrent shear zones that cut and limit the body of N4; the last set corresponds to the folds and crenulations present throughout the entire ore body. These sets of structures are interpreted in the context of a single deformational event. The lithotypes that make up the manganese mine (Blue) are classified into three types: Protomines, Surface Deposits and Subsurface Deposits. Mining is currently being carried out in the central part of the deposit, between the LT00 and LT800E lines, where the ores related to surface and subsurface deposits were identified. The first includes pisolites (PIS), blocks (BL), platelets (PLT) and manganese breccias (BLM), and the second encompasses manganeseiferous mudstones (PM), granulated manganese material (MMG) and massive manganese material (MMM). The various types of manganese ore are wavy, defining synformal and antiformal structures oriented in the E-W direction and associated with strongly inclined thrusts to the north. The N4E and Azul mines are located on the northern edge and in the central-north region of the divergent macrostructure of Serra dos Carajás, respectively. Such a regional geometric arrangement is interpreted as a positive flower structure associated with an E-W sinistral binary. In this sense, the lithostructural units of the two studied areas must be understood as fractions of an inverted transcurrent volcano-sedimentary basin.Item Acesso aberto (Open Access) A associação geoquímica Au-As-B-W-Cu-(Sn) em solos, colúvios, crosta laterítica e gossans no alvo Águas Claras-Carajás(Universidade Federal do Pará, 1997-05-07) COSTA, Newton Cunha da; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432The studied area called Alvo Águas Claras, is located in the Mineral Province of Carajás, southwest of the State of Pará, which represents one of the largest mineral provinces in the world. It is an important area for gold research, which has been prospected since 1991 by DOCEGEO, a subsidiary of Companhia Vale do Rio Doce – CVRD. This target is located in a region of dense rainforest cover, whose geological profiles are highly weathered, showing similarities with the gold deposits described in several other regions of West Africa and Australia. In the Amazon region, the older lateritic profiles are undergoing intense alteration since the end of their formation in the Lower Tertiary, with consequent distribution of these profiles and formation of soils or colluviums. The objective of this work is the detailed study of the behavior of gold, on the surface of this truncated lateritic terrain, and its relationship with trace elements such as B, W, Sn and Cu, in latosols, colluviums and outcropping laterite-gossanic crusts in the area. Thus, a detailed geochemical and mineralogical study of this material was developed, in order to assist in the identification of geochemical signatures indicative of the primary nature of mineralizations and associated rocks, in addition to the evaluation of the dispersion and mobility of these elements during the transformations of the lateritic and gossans crusts. in latosols and colluviums, to establish criteria for geochemical prospecting of these bodies in deeply weathered regions. The work methodology consisted of a field phase, developed on the mineralized bodies denominated by DOCEGEO as Corpo da Anomalia Au/As and Corpo do F-23, with the objective of geological reconnaissance of the area, description of the units and collection of samples of surface. The samples collected were mostly oxisols, colluviums, lateritic crusts, gossans, in addition to host rocks (sandstones and siltstones) and quartz veins. The analytical treatment consisted of several phases such as: drying, quartering and separation of 200g aliquots for pulverizing and 100g for separating heavy and insoluble minerals from pre-selected samples, through the highest levels of boron and gold. Petrographic analyzes were performed using an optical microscope with reflected and transmitted light. All samples were submitted to X-ray diffraction analysis, where both the total sample composition and the different domains of complex samples and isolated minerals were analyzed. A detailed mineralogical study was carried out on tourmalines, involving the calculation and refinement of the unit cell parameters. Quantitative analyzes of the minerals, as well as detailed photographs, were carried out by Scanning Electron Microscopy, with Dispersive Energy System, involving gold particles and other associated heavy minerals. In the geochemical analyses, the following major elements were analyzed: Fe2O3, TiO2, P2O5 through colorimetry; SiO2 and loss on ignition (P.F.) by gravimetry; Al2O3 by titrimetry; Na, Mn, K, Mg by atomic absorption, and some trace elements including Au. In the statistical treatment of data, correlation studies were mainly used, based on Parson's correlation coefficient (r), through binary correlation diagrams, correlation matrices and dendrograms of cluster analysis in R-mode. Isovalue maps were made for Au, B, W, and As, in order to better visualize the surface dispersion of these elements. The geology of the area is characterized by different outcropping and sub-outcropping supergenic materials, which can be juxtaposed in the form of the following composite profile, from top to bottom: Soil horizon (latosol), Colluvium horizon, Lateritic crust and Gossans, the latter being the main gold mineralized bodies prospected in the Águas Claras area. The mineralogy of the entire profile is basically represented by quartz, kaolinite and iron oxides-hydroxides, in different proportions. Accessory minerals such as tourmaline, wolframite, cassiterite and muscovites are frequently found, occurring in varying amounts, practically in all samples. The mineralogical composition found in the various materials analyzed is quite simple in terms of the variety of minerals, but the proportions of the mineralogical phases vary greatly, even within samples from the same horizon. The minerals that represent the greatest distribution among the samples are quartz and hematite. The first occurs abundantly in the oxisol, decreasing significantly in the lateritic crust samples with almost total disappearance in the gossans samples, while the behavior of the hematite is the opposite. The geochemical associations obtained through the multi-elementary analyses: Oxisols: 1) As – Cu – B – Au – W - (Mn) - (Pb); 2) Cr – V – Ga – Mo – Ni – Zn; Colluvium: 1) As – Y – Cu – Mn – Pb – Mo; 2) Au – W – B – F; Lateritic crust: 1) As – W – Au – B – F – Sn; 2) Cu – Ni – Pb – Zn – Sc. The most characteristic geochemical association in all horizons is that represented by Au-B-W-As, possibly with Sn-Cu-F, which must reflect the geochemical signature of the Au-sulfide primary mineralizations, in addition to the influence of the host sediments in addition to the granitic intrusions. Other associations or pairs of correlations involving Cr-V-Ga-Mo-Zn are related to the ease of these elements being incorporated into the structure of iron oxides and hydroxides, abundant in all studied horizons. The gold particles found in the various horizons, have quite varied morphology and purity, which may indicate the presence of several stages of mobilization of this metal in the supergenic environment. As for the trace elements, there are strong anomalies of W, Sn and B, with the minerals responsible for the high levels, respectively, wolframite, cassiterite and tourmaline, the latter belonging to the compositional field of dravita-schorlite, rich in iron , getting very close to the field of ferridravites. Within the above, it can be said that despite the mineralogical simplicity, the concentration of trace elements is quite heterogeneous, but with characteristic signatures that remain in different horizons and that allow delineating the mineralized supergenic bodies and inferring the composition of the primary bodies. The understanding of the dispersion and the characterization of these geochemical signatures prove to be of great importance in geochemical prospecting, in the exploration of other bodies of similar nature in the region.Item Acesso aberto (Open Access) Estudo geocronológico e de geoquímica isotópica da área Pojuca (Província Mineral de Carajás - PA)(Universidade Federal do Pará, 1996-03-15) SOUZA, Sandro Rogério Balieiro de; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136The Pojuca area, located in the northern portion of the Mineral Province of Carajás (southeast of the State of Pará – Brazil), presents Archean units such as: metavolcano-sedimentary sequences of the Igarapé Pojuca Group, with important deposits of Cu (Au, Ag, Mo); deformed granites (Itacaiúnas Deformed Granite); sedimentary rocks of the Águas Claras Formation; and metagabbroic dykes. The Pojuca Granite is an intrusive Proterozoic body in Archean rocks. Geochronological and isotopic geochemical studies were carried out on these lithologies using the methods Pb-Pb by evaporation in zircon, Pb-Pb in whole rock and phosdspar and Rb-Sr in whole rock and minerals (all results calculated with deviations of 2σ) . In the metavolcanic rocks of the Igarapé Pojuca Group two distinct types of zircon (metamictic and non-metamictic) were observed. Metamitic zircons show high contamination of foreign Pb, possibly caused by the action of hydrothermal fluids during thermal events (Archaean regional metamorphism, intrusions of the Itacaiúnas Deformed Granite and the Pojuca Granite). The non-metamictic zircons did not show Pb amounts detectable by the mass spectrometer. The analyzes carried out by the Pb-Pb method in whole rock and feldspars did not provide good results due to the dispersion of the analytical points in the graph 206Pb/204Pb vs. 207Pb/204Pb. However, the values of the Th/U ratios (2.5) indicated a mantle source for the metavolcanic rocks. The Pb-Pb method by zircon evaporation was successfully applied to the Itacaiúnas Deformed Granite, obtaining an age of 2560 ± 37 Ma, interpreted as the minimum crystallization age of these rocks. Confirming for this body an Archean age close to that previously obtained by the Rb-Sr method in whole rock (2480 ± 40 Ma), being the same correlated to the age of the Ancient Salobo Granite (2573 ± 2 Ma, U-Pb in zircon). Analyzes by the Pb-Pb method on whole rock and feldspars did not provide good results on the Itacaiúnas Deformed Granite. The ages obtained (1597 ± 13 Ma and 2215 ± 86 Ma) indicate a disturbance of the Pb isotopic system, possibly caused by the intrusion of the Pojuca Granite. This same event affected and rehomogenized, on a mineral scale, the Rb-Sr system of this body, as indicated by the Rb-Sr age in whole rock and minerals (1810 ± 57 Ma). In the Pojuca Granite, only one zircon made it possible to obtain an age of 1873 ± 59 Ma, similar to the previously obtained U-Pb age in zircon (1874 ± 2 Ma). Using the Pb-Pb method in whole rock and minerals, the age of 1856 ± 23 Ma was obtained for the Pojuca Granite, also interpreted as the crystallization age of the body. The value of µ = 10.5 ± 0.32, as well as the high ratios 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, indicate a crustal source for the granitic magma. The zircons of metagabbroic rocks (dikes) are petrographically similar to the metamict zircons of volcanic rocks. It is not possible to obtain satisfactory geochronological results. In the rocks analyzed by the Pb-Pb method in whole rock and feldspars from the Pojuca area, very high 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios were found. In the Itacaiúnas Deformed Granite and in the Pojuca Granite these ratios are interpreted as a product of the enrichment of the source magmas of these granites in the U and Th elements. In metavolcanic rocks it is believed that the high ratios reflect an isotopic contamination due to hydrothermal fluids associated with the intrusions of the Itacaiúnas Deformed Granite and the Pojuca Granite. Plotting the Pb isotopic ratios on the 206Pb/204Pb vs. 208Pb/204Pb, 204Pb/206Pb vs. 207Pb/206Pb and 204Pb/206Pb vs. 208Pb/206Pb, it is noted that each studied unit occupies a different domain. However, there is a slight overlap between the fields defined by the isotopic ratios of the metavolcanic rocks and the Pojuca Granite, which may indicate contamination of the metavolcanic rocks by granite.Item Acesso aberto (Open Access) Geoquímica dos sedimentos superdiciais de fundo do Estuário do Rio Maracanã, NE do Pará(Universidade Federal do Pará, 2006-04-05) DELFINO, Smaily Bastos; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429The Maracanã estuary is located in the northeastern of Pará State, within the Extraction Marine Reserve (Law 9.985/00), which has as primary goal to the sustainable use and conservation of the renewable ressources, protecting living conditions and the culture of the population, which consists of fisherman, small seliers and the local community. Due to its environmental characteristics, this area represents an important pole for the regional development. In this work, one of the aims was to search a geochemical formality to an interpretation of analytical results related to the geochemistry of the superficial sediments of the estuary of Maracanã bottom in order to determine the amount of heavy metais (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) of the granulometry with smaller fractions than 0,64 tem by atomic absorption spectrometry, to obtain the current inexistent background leveis. In the Maracanã estuary, it was registered much more silt-clay fraction than sand fraction, besides mineralogical similarity that indicates presence of kaolinite, illite and smectite. The amount of organic matter (MO) (5,4±0,70%) in sediments was homogeneously distributed. The pH didn't vary much, only between weakly acid (6,48) and weakly alkaline (7,13). Heavy metais - 1) in Maracanã river estuary cadmium concentrations were under of the equipment detection limit (0,009 ppm); 2) Cobalt varied from 46 to 55 ppm (50,97 ± 2,31 ppm) in total fraction, and from 5 to 7 ppm (6 ± 0,37 ppm) in bio-available fraction; 3) Cromo varied from 126 to 152 ppm (140,33±6,56 ppm) in total fraction and from 17 to 24 ppm (20,73±1,7 ppm) in bio-available fraction; 4) Copper varied from 17 to 21 ppm (18,97±1,19 ppm) in total fraction and from 6 to 9 ppm (7,0 ± 0,69 ppm) in bio-available fraction; 5) Iron varied from 3,4 to 4,6 % (4,14± 0,24 %) in total fraction and from 1,5 to 1,9 % (1,66± 0,1 %) in bio-available fraction; 6) Manganese varied from 293 to 545 ppm (423,53±74,63 ppm) in total fraction and from 168 to 499 ppm (335,1±91,3 ppm) in bio-available fraction; 7) Nickel varied from 44 to 53 ppm (48,77 ± 2,27 ppm) in total fraction and from 7 to 9 ppm (8,03±0,56 ppm) in bio-available fraction; 8) Lead varied from 42 to 48 ppm (45,63±1,69 ppm) in total fraction and from 14 to 17 ppm (15,13±0,78 ppm) in bio-available fraction; 9) Zinc varied from 72 to 85 ppm (78,83±3,44 ppm) in total fraction and from 26 to 32 ppm (29,43±1,65 ppm) in bio-available fraction. Concentration values of the bio-available heavy metal analyzed are smaller than those VGQS (Guide-Value of Sediment Quality), established by the "Canada Environmental Agency" (AAC) and the "National Oceanic and Atmospheric Administration"(NOAA), indicating that it should rarely occur bad effect on local biota. Considering that the area is an extraction reserve and that were not found evidence of anthropic contamination associated with the heavy metais, neither in their total fractions nor in their bio-available fractions in the Maracanã estuary, it is possible to consider that the data obtained from both analyzed geochemical fractions of heavy metais represent a value dose to the characteristical background of the region. Therefore, the Maracanã estuary is a reference cite to study the biogeochemistry and ecotoxicoiogy of the sediments of similar environments in Coastal of the Pará State. Besides that, the data obtained in this work can provide a subside for future geochemical and environmental surveys in the area, once that concentration ranges and reference values for many heavy metais that are present in the bottom sediments of this estuary were established.Item Acesso aberto (Open Access) Organização lito-estrutural do duplex Salobo-Mirim Serra dos Carajás(Universidade Federal do Pará, 1990-06-06) SIQUEIRA, José Batista; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286The Salobo Group embodies a sequence of volcanosedimentary rocks, which overlain a sialic basement, and is linked to the evolution of the Cinzento Transcurrent System, situated immediately to the north of the transcurrent system which provided the estabelishment of the Grão-Pará Group. The macrostructure is formed by two major shear zones which join at the west and east end parts of the studied area, defining a WNW-ESE eliptcal structure. This structure, which is interpreted as an extensional duplex, comprises, internally, minor shear zones that converge to the main zones. NW-SE, NNE-SSW and NE-SW strike-slipe zones modify the major geometric pattern. The duplex lithologies underwent metamorphism of the amphibolite facies during regional transpression, followed by expressive hidrotermalism and greenschist facies transformation trought the progress of the deformation. Significant mineralizations of bornite, chalcocite and in some cases chalcopirite, with molibdenite, gold and silver, are mainly hosted by lenses of iron formations, besides magnetite. These sulphides are distrubuted as inclusions in the grains of silicate gangue minerals and oxides or between them, as well as along the ductile and ductile-ruptile features, such as milonitic S-C foliations and R, R', p and y=D fractures, showing the manifold origin of such mineralizing fluids. Two kinematics models can be visualized to explain the main litho-structural units: sinistral stike-slip system involving transtension, followed by transpression and then transtension; and crotonic reworking related to transtension regime.