Navegando por Assunto "Serra dos Carajás - PA"

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Alteração supergênica das rochas básicas do grupo Grão-Pará: implicações sobre a gênese do depósito de bauxita de N5 - Serra dos Carajás
(Universidade Federal do Pará, 1981-11-19) LEMOS, Vanda Porpino; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
The present study deals with the supergene alteration of the basic volcanic rocks of the Grão Pará Group and gathers evidences that support the N5 bauxite deposit (Carajás Sierra) to be an extreme product of this alteration. In the lack of a continuous profile, this hypothesis was tested with a composed profile using the subsurface information available for the contiguous N4 plateau where the whole weathered sequence could be observed. The bauxite-rich and lateritic horizons, only developed in N5, were then assumed to be a part of that sequence and taken as its more superficial levels. The basic volcanic rocks are of precambrian age and were classified as tholeiitic basalts compositionally similar to those of the calc-alkaline suites that occur in modern island ares (TiO2-Zr/P2O5 diagram). The primary mineral assembly is dominantly composed of labradorite and pigeonite-augite and has zircon, ilmenite and opaque minerals as the major accessory phases. Hydrothermal activity caused mineralogical changes in theses rocks producing chlorite, epidote, calcite, sericite, amphibole and quartz. Significant chemical and mineralogical changes were induced by the weathering in these rocks and could be evaluated to depths up to 140 m. The serbidecomposed material showed substantial losses of CaO, Na2O and FeO (this due to partial oxidation to Fe+3) and less important lasses of SiO2, MgO and K2O. In contraposition there was relative enrichment of Fe2O3, Al2O3, TiO2 and P2O5 besides major gains of H2O. This new chemical environment favored the formation of compatible stable phases represented, in order of abundance, by chlorite, smectite-chlorite, opaque minerals and quartz. The totally decomposed basalts revealed an aimost complete loss of alkalls, MgO and CaO, with SiO2 contents dimishing to values of approximately 40% of its initial quantities. This enhanced great relative gains of Fe2O3, Al2O3, TiO2 and P2O5 and H2O with respect to the previous alterations stage. The resulting mineral assembly turned out be dominated by kaolinite, goethite and titanium oxides, and secondarily by gibbsite and quartz. Determinations of Cr, Ni, Co and Zr were done for both the bas.alts and its weathered equivalents. Enrichment factors of the order of 1.5 to 5.0 generally progressive towards the surface indicate the greater or lesser mobility of these elements within the supergene environment. Cr, Ni and Co were retained by coprecitpitation with iron hidroxides while Zr was accounted for by the preservation of zircon as a residual mineral. The N5 bauxite deposit consists of a gibbsite-rich upper layer with an average thickness of 4.7 m and average chemical composition of 3-.13% SiO2, 2.3% TiO2, 47.0% Al2O3, 23.0% Fe2O3 and 24.0% volatiles. Mineralogically it is composed of gibbsite, kaolinite, titanium oxides and iron hidroxides (goethite). The subjacent layers show distinct chemical constitution but the mineral suites differ in the proportions rather than in the kinds of the phases present. Downwards it is observed 1) a lateritic crust as thick as 10 m, 2) a gibbsite-rich clay that do not exceed 35 m in thickness and 3) an argillaceous horizon of indefinite thickness. The lateritic crust has an average chemical composition of 3.6% SiO2, 2.0% TiO2, 28.0% Al2O3, 47.0% Fe2O3 and 19.0% volatiles, and a mineralogy dominated by hematite, kaolinite, iron hidroxides, titanium oxides and subordinate quantities of gibbsite. The gibbsite-rich clay has average proportions of 24.0%, 2.0%, 28.0%, 32.0% and 13.0.% for SiO2, TiO2, Al2O3, Fe2O3 and volatiles respectively while the argillaceous horizon shows average proportions of 47.0%, 1.5%, 20.0%, 22.0% and 7.5% for these same components in that order. The mineral assembly of these two last levels is dominated by kaolinite, gibbsite, titanium oxides and iron hydroxides although hematite appears only in the gibbsite-rich clay while goethite and quartz appear, only ,in, the argillacebus horizon. The identification of heavy minerals in samples of both the decomposed basalt and the bauxite material revealed the same suite consisting of ilmenite, zircon and tourmaline, the latter mineral being found in greater abundances in the bauxite. Boron determinations from samples of the various horizons of both sequentes (N4 and N5) indicated contente that varied from 70 to 100 ppm, justifying /the probable presence of tourmaline even in the rocks from which was not possible to separate heavy minerals. The integration of all these data allowed the interpretation of the N5 bauxite plateau as a residual deposit of the supergene alteration of the volcanic basic rocks of the Grão Pará. Group with basis on 1) the chemical and mineralogical identities between the two sequences, especially the decomposed basalt and the gibbsite-rich clay, 2) the chemical correspondente that suggests the argillaceous horizon to be an intermediate stage of alteration between the semidecomposed and the decomposed basalt, 3) the presence of gibbsite in the decomposed basalt suggesting a stage of evolution which, given enough time and the appropriate conditions, could produce a material progressively rich in alumina and 4) typical trace elements of basic rocks present in relatively high concentrations in the bauxite deposit and, taken the genetic link for granted, showing enrichment or impoverishment factors along a common trend from the unaltered basalt to the bauxite material. Special attention was paid to the lateritic crust that formed underlying the bauxite deposit. It has been interpreted as a result of the relativo mobility of Fe and Pd, under Eh-pH conditions that favored the descending movement of Fe and the fixation of in the upper horizons.
Acesso aberto (Open Access)
Alvo Borrachudo, Serra dos Carajás (PA): rochas ígneas ricas em magnetita e apatita com mineralizações de sulfetos associada
(Universidade Federal do Pará, 1996-05-25) FARIAS, Edielma dos Santos; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
Acesso aberto (Open Access)
Análise faciológica e aspectos estruturais da formação Águas Claras, região central da Serra dos Carajás-PA
(Universidade Federal do Pará, 1995-01-31) NOGUEIRA, Afonso César Rodrigues; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553
Acesso aberto (Open Access)
Caracterização de espécies de Leishmania isoladas de Flebotomíneos sp. de três ecótopos da Serra dos Carajás, Pará, Brasil
(Universidade Federal do Pará, 2008) DIAS JUNIOR, Manoel Guacelis de Sena; ISHIKAWA, Edna Aoba Yassui; http://lattes.cnpq.br/3074963539505872
The American cutaneous leishmaniasis (LTA) is an infectious disease, with a high frequency of zoonosis, endemic in the Amazon region, transmitted by sand flies of generous Psychodopygus and Lutzomyia. Serra dos Carajás, located in southeastern Pará, is widely exploited by extractive companies and as a result, the LTA would be transformed into a major health problem to workers because of the practice of deforestation and construction of roads for drainage of the ore. The purpose of this study is to evaluate the natural infection in the sand fly by Leishmania in the Serra dos Carajás region through the PCR. Catches of sandflies were held in three different areas, Parque Zoobotânico de Quarentena, APA do Gelado and Tapirapé-Aquirí, with CDC-type of light traps and Shannon, during the night from the evening twilight. The sand flies captured were identified according to Young & Duncan, 1994, and frozen in N2. 5.947 sandflies were frozen, being 3.495 females and among these 550 specimens were tested. The extraction of DNA was performed using SDS and KOAc and it was precipitated with ethanol 96%. Subsequently, the PCR was performed by amplifying the mini-exon gene with the primers S1629 (5' GGGAATTCAATAWAGTACAGAAACTG 3') and S1630 (5' GGGAAGCTTCTGTACTWTATTGGTA 3'). The DNA of Leishmania was detected in 36 (6,5%) sand flies, 34 of subgenus Viannia detected in 30 Psychodopygus wellcomei/ complexus, three Lutzomyia whitmani and a Lutzomyia shawi. Two infections by Leishmania amazonensis was detected in Psychodopygus wellcomei/ complexus. Tapirapé - Aquirí, APA do Gelado and Parque Zoobotânico de Quarentena showed high rates of natural infection in sand flies 6.54%, 5.96% and 7.92% respectively. Ps. wellcomei/complexus still presents as Leishmania vector that cause LTA. Studies on the power of vector species Lu. whitmani and Lu. shawi naturally infected by Leishmania in the Serra dos Carajás should be intensified, if these species may be acting in the cycle of transmission of LTA in Serra dos Carajás. Studies that best explain the variation of the prevalence of different sandflies species and knowledge of the rate of infections should be also intensified in Serra dos Carajás.
Acesso aberto (Open Access)
Caracterização morfoestrutural e morfotectônica de áreas transpressivas: Serra dos Carajás e Serra do Tiracambú
(Universidade Federal do Pará, 1999-12-11) ESPÍRITO SANTO, Cláudia Vilhena do; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
Acesso aberto (Open Access)
Condutividade elétrica complexa de rochas
(Universidade Federal do Pará, 1979-08-14) ROCHA, Brígida Ramati Pereira da; SAUCK, William August; http://lattes.cnpq.br/6655455534234531
Laboratory measurements of complex conductivity were made on 28 drill-core samples from area MM1-Prospect 1 of the Carajás Mining District. The objective of this research was to help interpret field geophysical survey of the area using Induced Polarization and AFMAG methods. The laboratory measurements of amplitude and phase of conductance were taken in the frequency interval of 10-3Hz to 104Hz. The method used was the direct measurement of impedance using a memory osciloscope, a signal generator, and two high input impedance differential preamplifiers. The electrode system chosen for the measurements was the 2 electrode platinized-platinum because its frequency response is flat in the frequency range used. AlI the measurements were made at a constant temperature of 24°C±1°C. A petrographic study of the samples was done, using thin sections, polished sections and X-ray diffraction. Copper content, in the form of sulfides, was determined using atomic absorption. As a result of the petrographic study, the samples were classified in five distinct groups: granite, biotite schist, amphibolite and magnetite quartzite-iron formation. The grade of Cu was variable in the five groups, ranging from 50 ppm to 6000 ppm. In the conductivity measurements it was observed that, among the five groups, the samples of iron formation gave the largest variations with frequency. The granite samples had spectra flatter than those of schist or amphibole. In conclusion, these measurements show that the field Induced Polarization and AFMAG anomalies near these three drill holes (F1, F2 and F3) are due primarily to the magnetic iron formation, and secondarily due to associated low-grade chalcopyrite mineralization.
Acesso aberto (Open Access)
Considerações sobre a anatomia funcional e adptativa de alguns sigmodontinae (Mammalia : Rodentia : Muridae)
(Universidade Federal do Pará, 2002-10-29) MELO, Cláudia Cristina de Sousa de Melo; TOLEDO, Peter Mann de; http://lattes.cnpq.br/3990234183124986
Among the mammals, the little rodents makes up a singular group. These animals have been in full evolutive process due to their capacity of reproducing and adapting to different habitats. Philogeneticly, the group still hasn't a sure characteristic and is very similar morphologically to rodents Sigmodontinae from Serra dos Carajás. Through this study of external features and some banes from post-cranium related to motions habit, we beheld: 1) The choice of the habitat in Serra dos Carajás area among the rodents seems not to be related to a phylogenetic standard; 2) It wasn't possible to set a relationship between ecological features and main morphological shape from post-cranium related to body-shape among Sigmodontinae; 3) the morphology of úmero and femur have a strong Phylogenetic sign which is another feature of subfamily Sigmodontinae; 4) the signs intermembal, crural e branquial weren't effective to identify the many way of motions among the rodents Sigmodontinae.
Acesso aberto (Open Access)
Contribuição à petrologia do granito central da serra dos Carajás
(Universidade Federal do Pará, 1980-09-02) ALMEIDA, Regina Célia Cunha; RONCAL, Juan Rolando Zuleta
This study was carried out in the central region of the Serra dos Carajás in the South of the State of Pará. The area referred to is underlain by a granite batholith, surrounded by basic volcanic rocks in the north-east and slightly metamorphised sedimentary clastic rocks. In order to characterize the petrogenetic nature of the granitic body, a study was realized of the petrography and petrochemistry of the various facies of the granite and of the country rocks. Petrographic and geochemical evidence suggests a magmatic origin for the granite of Carajás. During its consolidation the granitic magma underwent a slight differentiation in the formation of various facies. The intrusive character of the body is e4denced by the presence of contact metamorphism of the hornblende hornfels in the country rocks in the proximity of the contacts. The observed mineralogical association (orthoclase and plagioclase) indicates that the granitic body may be included in the SUBSOLVUS group in the classification of the Tuttle and Bowen (1958). The magma was probably originated by partial melting of older crustal rocks.
Acesso aberto (Open Access)
O direito fundamental ao meio ambiente do trabalho equilibrado em face da monetarização dos riscos: a análise do caso dos trabalhadores do Projeto Salobo desenvolvido no Sudeste do Pará
(Universidade Federal do Pará, 2017-04-28) VIEIRA, Lucas Rodrigues; NASSAR, Rosita de Nazaré Sidrim; http://lattes.cnpq.br/2092928958819725
The present dissertation deals with the problems related to the ineffectiveness of the fundamental right to the environment of work, especially due to the adoption of a purely monetarizing policy of risks that is only concerned with financially compensating workers for exposure to agents harmful to their life and health, As verified in the labor demands related to the Salobo Project developed in the Southeast of Pará. Thus, the main objective of the work is to verify the legal instruments that can be used to promote a healthy labor habitat for employees, as a way of protecting physical integrity and consequently reduce the rates of industrial accidents and occupational diseases, to the detriment of discussions restricted to the imposition of additional remuneration (additional to insalubrity and dangerousness) that do not serve to encourage the adoption of medical norms and security job. For this, the dissertation carried out a survey of the doctrine and the national and international legal order, as well as qualitatively analyzed four judicial processes of the Salobo Project judged by the Regional Labor Court (TRT) of the 8th Region in the last two years. The work was constructed in three chapters. The first chapter addressed the definition, characteristics, and functions of fundamental law norms, based on the thoughts of Robert Alexy. Subsequently, historical, conceptual and legal aspects related to the work environment. The second chapter discussed the formation of the risk society, according to Ulrich Beck's theory. After that, the main risks arising from the work activity were discussed and the policy of mere monetization of environmental risks at work was discussed. Finally, the third chapter examined the working conditions of workers in the Salobo project developed in Southeastern Pará, based on lawsuits that were processed in the TRT of the 8th Region, and pointed out the alternatives to the realization of the fundamental right to the environment of balanced work. In conclusion, the research verified that the workers of the mentioned project were exposed to risks to their well-being, but only monetizing instruments were used that do not alter the conditions of the working environment, not making use of preventive and precautionary measures, such as, for example, inhibitory tutelages combined with temporary emergency orders.
Acesso aberto (Open Access)
Dispersão geoquímica dos elementos Si, Al, Fe, Mn, Na, K, Cu e Zn nos solos e sua aplicação na caracterização de áreas geoquimicamente homogêneas
(Universidade Federal do Pará, 1980-05-13) SILVA, Waldise Rossycléa Lima da; RONCAL, Juan Rolando Zuleta
Variations in the chemical composition of soils are used to characterize sub-areas geochemitally homogenous. The aplication of this methodology in a tropical humid region of accentuated topography constitute the principal objective of the present research. Samples of red latosols (Horizon B) developed over gravite, sandstone and basalt occurring in the Central Granite Region of the Serra dos Carajás, Pará State, Brasil were analized for the elements Si, AL., Fe, 40Mn, Na, K, Cu e Zn, by atomic absorption spectrophotometry. Based on the criterion of similarity in the chemical composition (Cluster Analysis, Factor Analysis) the soils were separeted in to different groups. The geographical distribution of the different groups permit the establishment of a Glose relationship between the different parent lithologies and their corresponding soils.
Acesso aberto (Open Access)
Distribuição dos elementos Si, Al, Fe, Ca, Mg, Mn, Ti, Cu, K e Na em solos desenvolvidos na região do granito central da Serra dos Carajás - sul do estado do Pará
(Universidade Federal do Pará, 1981-03-13) DAMOUS, Nina Rosa Leal; RONCAL, Juan Rolando Zuleta
The distribution of elements in the weathered pro rocks is effected mainly by climate, geomorphology and parent material. The present study deals with the distribution of Si, Al., Fe, Ca, Mg, Mn, Ti, Cu, K and Na in the weathered products of the Central Gravite at Serra dos Carajas - Para, Brazil, which occurs in an area which is characterized by ondulated relief and humid tropical climate. Samples representing two selected weathering profiles were collected to depths that did not exceed 6 m. The analytical treatment consisted of poten/biometric determinations of pH values, the determination of the chemical and mineralogical compositions of the sand, silt and clay fractions, and the determination of the chemical composition of the oxide fraction. The two profiles reveal an intensa process of feldspar removal from the parent granite and the formation of a sand-clayey lato-soil. In this process quartz has been preserved and clay minerals and aluminium and iron hidroxides have been formed constituting the dominant assemblage of the soil. Ca, Mg, Mn, Na and K from the parental rock were nearly completely leached away to the extent that these elements are only found in small amounts in the remaining feldspars or adsorbed on clay minerals. On the other hand, Ti present principally in resistant minerals, practically maintains its' original concentration. Cu is sligthly enriched in the profiles due to adsorption in the clay minerals. The presence of only very small amounts of feldspar along the profiles shows the great intensity of the weathering process acti.ng on the granitic rocks. The direct transformation of feldspar to clay minerals or aluminium oxides is related to the climatic conditions frainy and dry seasons) prevalent in the area.
Acesso aberto (Open Access)
Efeitos do strike das estruturas geológicas de duas dimensões nas pseudos-seções de IP resistividade
(Universidade Federal do Pará, 1983-12-22) GUIMARÃES, Paulo Buarque de Macedo; RIJO, Luiz; http://lattes.cnpq.br/3148365912720676
The IP-resistivity surveys carried out in the Carajás mineral district were not orthogonal to the geological structures because they were executed on lines already opened by the geochemistry crews. This fact motivated us to study theoretically the influence of the direction of the IP-resistivity survey lines with respect to the strike of the structure. We used Rijo's finite element program (1977), developed for surveys perpendicular to the structures, with the necessary adaptations. The main modification was in the inverse Fourier transform routine. For the simple case of the perpendicular surveys, the inverse transform is an easy discrete integral with seven points. However, for oblique surveys the integrand is oscillatory and therefore the integral to be evaluated is more complex. We adapted a method presented by Ting and Luke (1981) using eighteen points in each integration. It was found that the effect of the direction of the line with respect to the strike is negligible for angles greater than 60 degrees. For smaller angles the effect is to "open" the anomaly with minor changes in its center. There is no obvious way to compensate this effect with changes in the model parameters.
Acesso aberto (Open Access)
A espectografia de absorção infra-vermelha no estudo de alterações geoquímicas de minerais de cobre e silicatos associados (Região da Serra dos Carajás-Pa)
(Universidade Federal do Pará, 1989-07-31) SANTOS, Ana Lúcia Blanc dos; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
Acesso aberto (Open Access)
Espeleotemas fosfáticos em cavernas ferríferas de Carajás e uma nova ocorrência de esfeniscidita
(Universidade Federal do Pará, 2017-02-26) ALBUQUERQUE, Alan Rodrigo Leal de; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
Iron ore mining in Brazil is important for maintaining the country’s positive trade balance. Iron ore is among the country’s main exports, and as a result of intense extraction, new environmental policies have been implemented. In an attempt to balance economic activity and environmental conservation, an inventory and a relevance-based classification of caves were implemented in 2008 as criteria for environmental licensing of mining ventures. This implementation motivated the present study of phosphate speleothems in iron caves in the Carajás Mineral Province. The objectives of this study were to describe the phosphate minerals and their formation processes based on data from geochemical and petrographic analysis in concert with X-ray diffraction, differential scanning calorimetry coupled with thermogravimetry, infrared and scanning electron microscopy. We studied eight caves where the development of phosphate speleothems appeared to be directly associated with the presence of guano. DSC-TG curves allowed us to identify two phosphate groups: leucophosphite-spheniscidite, which displayed two endothermic events at 323.4 and 400 °C attributed to OH and NH4 removal, respectively, and strengite-phosphosiderite, which displayed no such events. Infrared spectra allowed us to identify the NH4 functional group, related to the presence of spheniscidite, based on absorbance bands centered at 1430 and 3040 cm-1. Values of the unit cell parameters for spheniscidite, calculated by Rietveld refinement, revealed dimensions and angulations slightly lower than those reported in the literature (a = 9.803 Å, b = 9.722 Å, c = 9.858 Å, β = 102.78°). These smaller values are attributed to increased substitutions of K for NH4 and Al for Fe. Based on the geochemical analysis, significant enrichment in P2O5, Zn, Ni and Rb was detected, suggesting that bat guano was a potential source of these elements. Guano decomposition releases phosphoric acid, which percolates the lateritic substrate reacting and substituting iron hydroxides for phosphate minerals, with simultaneous assimilation of metals that had been bioaccumulated and excreted by bats.
Acesso aberto (Open Access)
Estudo da alteração hidrotermal,com ênfase no metamorfismo sódico, de rochas granitóides e máficas da região de Canaã de Carajás, Província Mineral de Carajás
(Universidade Federal do Pará, 2007-06-25) SOUZA, Francisca D'ávila Soares de; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
The Sossego and Serra Dourada areas are located in the southern part of Carajas ridge, at the contact zone between the basement rocks (Xingu Complex; ~2.8 Ga) and the Grão Pará Group (2.76 Ga). Serra Dourada lies 15 km east of the Sossego deposit, at the transition strip that bounds the Itacaiúnas block and the Rio Maria granite-greenstone terrane. In the Sossego deposit granitoids, metavolcanic rocks, biotite-rich and mafic rocks were investigated, all of them were hydrothermalized and/or deformed to a greater or lesser extent. In Serra Dourada granitoids, their enclaves and mafic rocks were studied, the former being represented by unaltered, altered and milonitized varieties. The likely protoliths of the apogranitoids and metavolcanic rocks that occur in Sossego were syenogranites/granodiorites and porphyritic quartzodiorite/diorite, respectively, while the mafic altered rocks were derived from microgabros. The porphyroclastic texture of the biotite-rich rocks may be an evidence for their protoliths being, at least in part, the same as those of the metavolcanic rocks. Apogranitoids, metavolcanic and biotite-rich rocks have similar REE patterns, suggesting that they might be comagmatic, although some samples of the biotite-rich rocks show higher La/Yb ratios. Concerning the contents of less mobile elements (Nb and Zr), the metavolcanic and biotite-rich rocks are much more similar. Albitization, scapolitization, amphibolitization, chloritization, biotitization, epidotization and potassic feldspatization were the most important hydrothermal processes that affected those protoliths. Albitization is more common in the apogranitoids and acid metavolcanic rocks, whereas scapolitization is more typical of the biotite-rich and mafic rocks. In the apogranitoids two albite generations (I and II) were identified. The albite I represents crystals with chessboard texture produced by the replacement of potassium feldspar. Albite II is present in monomineralic veinlets which correspond to one of the latest stage of hydrothermal activity. Only albite I occurs in all granitoid varieties. In the mafic rocks two scapolite generations were recognized. One refers to crystals aggregates that replaced the primary plagioclase and the other to fine sinuous veinlets of scapolite+Mg-hornblende that, in these rocks, mark the latest stage of the hydrothermal alteration. In the biotite-rich rocks only scapolite I was identified. The scapolite that occurs in both the mafic and biotite-rich rocks have similar meionite (Me=27-28%) and Cl (3-4%) contents, and were most likely formed by a NaCl-rich fluid, with little influence of the rock composition. This fluid might have also been responsible for the production of albite in all analyzed samples. This albite is purer in the apogranitoids (Ab=98.5-99.3%) and the metavolcanic rocks (Ab=99-99.3%) than in the other rocks. In Serra Dourada area, the granitoids include syenogranites, granodiorite and tonalites as well as enclaves of tonalitic composition. Their mineralogical characteristics and calc-alkaline affinity allow them to be classified as I-type granitoids related to subduction with some influence of extensional regime. Most geochemical data indicate that they are cogenetic and have been produced by fractional crystallization. Albitization, scapolitization and minor biotitization were the most important types of alteration that affected those rocks, the first being restricted to the syenogranites, while the other two types are recorded only in the tonalites. The syenogranites present different degrees of alteration ranging from aposyenogranite without hydrothermal albite to albitite with ~75% of hydrothermal albite. In all granitoids, the hydrothermal albite is purer than the magmatic albite. Mass-balance calculations shows that, in relation to the average composition of syenogranites and for volume factors of 0.8-1.1, the albitites gained Na2O and Cu, and lost K2O, Ba, Rb, Sr and W. The scapolitized rocks resulted from the alteration of tonalites and are mainly characterized by scapolite-rich (up to ~70%) veins/veinlets that cross-cut the rocks. In the moderately altered varieties, the scapolite composition is richer in Na (Me=24%) and Cl (4%) in comparison to that present in veins and in the mylonitized granitoids. Massbalance calculations indicate that the formation of the scapolitized rocks was accompanied by losses of Al2O3, MgO, CaO, Sr and Zr and gains of Fe2O3(t), Na2O, K2O, volatiles, Rb, Ba and Cu. The fluids that caused albitization and scapolitization of the rocks were Na and Cl-rich and, apparently, the albitization of the syenogranites preceded the scapolitization of the tonalites. The scapolite composition seems to have been strongly controlled by the composition of primary plagioclase, as evidenced by its more calcic character in the mafic rocks than in the apotonalites. Estimates of Cl content (1-2%) of rocks from both areas were based on its concentrations in modal scapolite, biotite and amphiboles. The stability of scapolite requires high salinity fluids as those that have been reported in the Sossego deposit. No fluid inclusion data concerning the Na-rich fluids responsible for albitization and scapolitization in the Serra Dourada area are yet available, although the evidences, notably the abundance of scapolite, suggest an evaporitic or similar source.
Acesso aberto (Open Access)
Estudo da geometria e cinemática das rochas sedimentares arqueanas da mina do Igarapé do Azul – Carajás-PA
(Universidade Federal do Pará, 2006-09-18) SILVA, Daniela Cristina Costa da; PINHEIRO, Roberto Vizeu Lima; http://lattes.cnpq.br/3251836412904734
The Igarapé Azul Mn Mine is geologically situated along the Carajás Fault trace, in the central portion of the Carajás Strike-slip System. The Mn ore deposit is related to politic sedimentary rocks of the Azul Member on the basal portion of the Águas Claras Formation (Archaean). This unit overlain unconformably the Grão Pará Group (Nogueira et al., 1995). At present day three explotation pits are opened in the mine: (1) Main Mine (Mine 1); (2) Mine 2 and (3) Mine 3. In these locations excellent outcrops of siltstones intercalated with finegrained mudstones, sandstones and Mn-layers are exposed. These rocks are organized in folds and normal/reverse faults sets under heterogeneous deformation, partitioned in different scales. The geologic sections exposed in the mines show the dominance of siltstones intercalated with mudstones in contact with pelitic manganesiferous rocks and ore (Mn bioxide). Primary structures such as hummocky stratification, cross stratification and parallel laminations are common in these rocks. Bedding with thickness of centimeters to a few meters (30-50 cm) represents the main primary structure, used as the main deformation marker observed in rocks. The Igarapé Azul Mn Mine is divided into two blocks separated by normal fault with displacements of tens of meters, where the north block is up in relation to the south one. The south block is poorly deformed, with irregularities in bedding which dips at shallow angles towards south, subsequently positioning the ore layer in deeper levels at S direction. In the north block bedding shows heterogeneous behavior. Deformation is more expressive in this region, with the ore deformed by folds and reverse faults. Faults show vertical along-dipping kinematics with dextral conjugated displacements of oblique character. This region can be defined as a major strain corridor. The kilometer-scale corridor observed at the north block follows the NW-SE trend, in concordance with the main domains separated by the faults described above, characterized as curvilinear asymmetric folds with NW and SE shallow plunge axes (10º-25º). These folds are sectioned by sinuous NW-SE and/or E-W normal faults with shallow dips (10º-30º) associated with dextral strike-slip faults, which generate drag folds. Straight or sinuous NW-SE reverse faults and sub-vertical fault zones are observed. The individual folds in this area are flexural reverse structures with en echelon geometry and similar orientation to the curvilinear folds: shallow SE plunging axes. The features described above drawn a gentle kilometer-scale antiform, which results from bedding accommodation in response to the faulting deformation. The parallelism of the features observed in the Igarapé Azul Mn Mine and the main lineaments which drawn the Carajás Fault suggest a close relation between important deformational episodes occurred during the tectonic history of the Carajás Fault. Faults with normal kinematics associated to directional dextral component of displacement are the major exposures in the area and are related to the dextral transtensional episode responsible for installation of the Carajás Fault prior to 2.6 Ga (Pinheiro, 1997). Folds, thrust faults and subvertical fault zones would be related to deformation under sinistral transpressional regime; a second event responsible for the reactivation and tectonic inversion of most of the primary structures near the Carajás Fault zone (Pinheiro, 1997; Pinheiro e Holdsworth, 2000; Lima, 2002).
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Estudo geoquímico do sistema hidrotermal relacionado à mineralização cuprífera da área Bahia, Serra dos Carajás, Pará
(Universidade Federal do Pará, 1989-10-24) RIBEIRO, Ana Maria Rodrigues; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983
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Estudo petrográfico, geocronológico e tipológico de zircão de rochas associadas às do grupo Grão Pará, Serra dos Carajás, Pará
(Universidade Federal do Pará, 2018-10-24) RODRIGUES, Anderson Sérgio Batista; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
In the Carajás basin, northern Mineral Province of Carajás, sequences of volcanosedimentary rocks with ages between 2.76 and 2.73 Ga make up the Itacaiúnas Supergroup. This supergroup encompasses the Igarapé Salobo (2.76 Ga), Grão Pará (2.76 Ga), Igarapé Bahia (2.74 Ga) and Igarapé Pojuca (2.73 Ga) groups. The proximity of ages and the lithological affinity of these units indicate that possibly these rocks have been formed under the same geological context, being different expressions of the same event. The Grão Pará Group consists of two formations: a thick sequence of volcanic rocks (Parauapebas Formation; 2758 ± 2 Ma, U-Pb in zircon), and jaspilites with iron ore (Carajás Formation). In view of the great difficulty of understanding the geographic and geochronological limits of the Grão Pará Group, it was carried on petrographic, geochronological (Pb-evaporation in zircon) and typological study of zircon crystals from of samples associated with the Carajás and Parauapebas formations. Rocks from the Grão Pará Group, as well as the majority of the archaean rocks of the Carajás basin, are hydrothermally altered in different degrees of intensity, irrespective of their lithological type. However, a great number of primary textural features were preserved and petrographic studies allowed the classification of the igneous rocks into two distinct groups: the basalt of dark gray to greenish coloration, fine granulation, mainly intergranular texture, from the Parauapebas Formation; and gabbro with intergranular texture, subofitic to micrographic intensively hydrothermalized (mainly serecitization) from dikes which cut the whole sequence. For the Serra Sul of the Carajás basin, two samples of saprolite of volcanic rocks interbeded with the iron formation and collected in cores from drill holes, were analyzed in this work. Due to the advanced weathering that affected these samples, a typological study of zircon was used in an attempt to identify the previous rocks, which allowed to classify the lithotypes as monzogranitealkaline granite affinity. Pb-evaporation method on zircon crystals, in two samples of volcanic rock saprolite interspersed with the iron formations belonging to the Carajás Formation indicated, indicated ages of 2745 ± 2 Ma for sample FS11D-161 and 2746 ± 2 Ma for sample FS11D-122, understood as time of crystallization of the analyzed crystals and the formation of volcanic rock which contains them. In addition to the high accuracy of these data, they are in perfect agreement with each other and within the gap established for the Itacaiúnas Supergroup. Moreover, because the dated samples come from rocks interbeded with the iron formation, they can be coeval (lava flow) or xi younger (intrusive), and establish a minimum limit for the deposition age of this formation. On the other hand, the age of the Parauapebas Formation, button of the Grão Pará Group, establishes the maximum age for Carajás Formation as 2759 ± 2 Ma. Therefore, the Carajás Formation was deposited in about 15 million of years, which is coherent for the estimated thickness of 400 m. In addition, the Grão Pará Group is covered by the Igarapé Bahia Group, whose volcanic rocks from the button are 2745 ± 1 million years old, which perfectly coincides with the ages obtained in this work. This age corroborates the the gap proposed for the deposition of the Carajás Formation, that is, a maximum of 15 million years. Additionally, the insignificant age difference proposed here for the Carajás Formation and for the volcanic from the Igarapé Bahia Group suggests that all these rocks are part of a same sequence.
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Estudo químico e atividade antibacteriana do fungo endofítico Scedosporium apiospermum de Bauhinia guianensis e de fungos da Serra de Carajás
(Universidade Federal do Pará, 2016-06-22) CORDEIRO, Jorgeffson da Silva; MARINHO, Patricia Santana Barbosa; http://lattes.cnpq.br/4826647905254039; MARINHO, Andrey Moacir do Rosario; http://lattes.cnpq.br/2511998363000599
Endophytic fungi are microorganisms that lives in association with the host species, and they're a promising source of important natural products. With a equal importance, the soil fungi also are capable of producing so many substances of economic value. Thus, the following work was objective to obtain bioactive composts produced by endophytic fungi M. acutistipula var. ferrea and soil Carajás Saw, besides the endophytic S. apiospermium from liana of Bauhinia guianensis Auble. The species M. acutistipula var. ferrea, were isolated 56 endophytic and 64 soil fungi. They were randomly, selected, 12 fungi to be reactivated in Petri dishes containing PDA medium. After reactivating the micro-extracts of 12 fungi were obtained as the adapted methodology Smedsgaar. The micro-extracts were evaluated by HPLC-DAD to determine the chromatographic profile and, also, submitted antimicrobial testing. The FSF 12 (trichoderma sp.), selected after the screening of chemical and biological profile was grown on a large scale in a solid medium (rice) and led to the isolation of five substances: fatty acid polyunsaturated (E1), 5'-inosil (E2), tyrosol (E3), harzialactone A (E4) and 2-anhydro mevalonic (E5). In relation to the fungus EJCP13 (S. apiospermium) where compounds isolated, triacyl (J1), ergosterol peroxide (J2), ergosterol (JA19), cerivisterol (JA29), methylester (JA24), dulcitol (D), and brefeldin A (JA). The compound Brefeldin A showed significant antimicrobial activity and, also, proved to be the major secondary metabolite in extracts from S. apiospermium. Thus, it decides to quantify a substance in the extract, which corroborate results, which indicate the presence of brefeldin A only in AcOEt and the hexane extracts. The isolation of the substances was performed by chromatographic techniques, such as CCVU and, monitoring, by ADCC. The chemical structures were elucidated with the aid of spectroscopic (1H and 13C NMR, HMQC, HMBC), and spectrometric (ESI-MS).
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Geocronologia U-Pb, classificação e aspectos evolutivos do Granito Marajoara – Província Carajás
(Universidade Federal do Pará, 2018-01-24) SANTOS, Rodrigo Fabiano Silva; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The Marajoara granite (MjGr) is a stock intrusive in mesoarchean granitoids of the Rio Maria domain, which is formed mainly by leucocratic rocks, represented by equigranular (BMzE) and heterogranular (BMzH) monzogranite facies. Rapakivi texture and occurrences of porphyritic granite (EGp) and microgranular enclaves (EMg) are restricted to BMzH facies. Such varieties have similar mineralogy: microcline, quartz and plagioclase occur as essential minerals; biotite partially altered to chlorite as the only varietal phase; zircon, titanite, opaque, apatite and allanite as primary accessories; and chlorite, sericite-muscovite, epidote, fluorite and clay minerals as secondary phases. The high magnetic susceptibility (SM) values (2.3-6.5 x10-3) and the frequent presence of magnetite show that the BMzH facies is akin to granites with magnetite series, whereas the BMzE variety shows affinity with the ilmenite series considering the modal opaque contents ≤0.5%, low values of SM (<0.15x10-3), and ilmenite as the sole Fe-Ti oxide. These rocks are, in general, peraluminous and have high FeOt/FeOt+MgO ratio, similar to the ferroan granites. In addition, they have geochemical affinities with intraplate A-type granites, which have crustal origin, wherein a significant variation of FeOt/(FeOt + MgO) found for these rocks [EGp (> 0.82); BMzH (> 0.86); BMzE (> 0.97)], allow them to be classified as oxidized (BMzH and EGp) and reduced (BMzE) Atype granites, that are related to the Jamon and Velho Guilherme suites, respectively. Differently from this, the EMg show clear affinity with the magnesian granites and the calcalkaline series. Evidence of magma mixing and geochemical modeling calculations demonstrate that EGp originate from the interaction of EMg (60%) and BMzH (40%) liquids. The compositional gaps existing among the several varieties that constitute the MjGr, as well as their compositional contrasts, suggest that their magmas are not cogenetic. The EMg represents a basic magmatism from the enriched lithospheric mantle that would have been injected into the magma chamber during the underplating process and at different phases of the granitic magma crystallization. The U-Pb zircon isotopic analyzes (SHRIMP) yielded an age of 1885 ±6Ma, interpreted as the crystallization age of MjGr. The MjGr was emplaced at shallow crustal levels (epizone) in an extensional tectonic environment with the effort following the trend NNE-SSW to ENE-WSW. The concentric zoning in the MjGr and the rheological behavior of its country rocks as well as the reduced or no influence of the regional efforts during the emplacement of the pluton indicate that the transport of the magma occurred through dikes. It is suggested that the construction of the MjGr was a result of the vertical rise of magmas through fractures and accommodation along the planes of the regional EW foliation, followed by a change of the vertical flow by a lateral scattering of the magma, analogous to the admitted model for the emplacement of the tabular batholiths of the Jamon Suite.