Navegando por Assunto "Granito"

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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.
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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.
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Estudo das relações de contato do granodiorito rio Maria com os granitos musa e jamon e com diques do proterozóico
(Universidade Federal do Pará, 1996-08-10) SOARES, Claudomiro de Melo; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
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Geocronologia Pb-Pb e Pb-Sr das rochas graníticas da região de Redenção, sudeste do estado do Pará
(Universidade Federal do Pará, 1996-01-05) BARBOSA, Alayde Alfaia; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
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Geologia e geoquímica do maciço granítico arqueano Xinguara e de sua encaixantes, sudeste do estado do Pará
(Universidade Federal do Pará, 1995-12-12) LEITE, Albano Antônio da Silva; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
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Geologia e metalogênese do depósito aurífero São Jorge, Província Aurífera do Tapajós, Novo Progresso-PA
(Universidade Federal do Pará, 2011-01-05) BORGES, Antonio Wanderlei Gomes; SANTOS, Márcio Dias; http://lattes.cnpq.br/6977793618030488
The São Jorge gold deposit lies in the easternmost part of the Tapajós Gold Province, SW portion of the State of Pará, far around 88km from Novo Progresso city. The São Jorge deposit comprises a mineralized quartz vein system hosted by the Young São Jorge Paleoproterozoic granite and it is controlled by a NW-SE trending shear zone. The Young São Jorge granite is an oxidized calc-alkaline monzogranite stock, characterized as magmatic arc type and correlated to the Tropas Intrusive Suite. The São Jorge shear zone is a brittle-ductile sinistral strike-slip shear zone which belongs to a regional structure known as Tocantinzinho Lineament. The thicker lodes, of metric width, are hosted by NW-SE main shear direction, whereas thinner veins in the NE-SW direction make middle to high angle in relation to the chief shear direction. Such a structural situation is compatible to the Riedel system, with parallel lodes hosted by main shear direction (Y/D) and gash veins in extension fractures (T). Minor stockwork veinlets complete the São Jorge vein system. The mineralized veins are always involved by hydrothermal alteration halo. Early alteration is characterized by chloritization of the ferromagnesian minerals (biotite and hornblende) which yielded chlorite+carbonate+magnetite mineral assemblage, followed by sodium metasomatism (albitization) of the K-feldspar and saussuritization of the plagioclase which generated sericite+carbonate+epidote assemblage. Intensification of that process evolved to phallic alteration (phengite+quartz+pyrite assemblage) associated to minor chloritization and sufidation (pyrite+ chalcopyrite+sphalerite assemblage). The gold-bearing ore, hosted in quartz veins, occurs in deep hydrothermal altered rocks, associated to sulfides (chiefly pyrite) and, more rarely, chalcopyrite and sphalerite. Galena, bismuthinite, native bismuth and gold are minor metallic phases. Free gold also occurs in hydrothermal quartz and magnetite. The main gangue minerals associated to ore are quartz, phengite and chlorite. Carbonate, rutile and zircon are minor gangue phases. Three types of fluids were recognized in the São Jorge deposit from fluid inclusion studies: 1) low-middle-salinity aqueous H2O-NaCl-KCl fluid, interpreted as meteoric water; 2) middle-salinity aqueous H2O-NaCl-CaCl2-MgCl2 fluid, with homogenization temperature ranging from 120 to 230°C, interpreted as magmatic brines; and 3) low-middle-salinity aquocarbonic H2O-CO2-NaCl fluid, with homogenization temperature ranging from 260 to 350°C, probably of magmatic or metamorphic origin. The magmatic saline aqueous fluid was interpreted as the ore fluid which transported the metals (mainly gold), the clorine, and the oxidized sulphur (SO2), concentrated in the residual phase of a granitic magma, whereas the aquocarbonic fluid transported the majority of CO2 and the reduced sulphur (H2S). The temperature and pressure conditions for the São Jorge gold deposit were established by combination of hydrothermal chlorite geothermometry and isochore calculated from the fluid inclusion microthermometric data. The temperature values for trapping the ore fluids range from 280°C to 360°C and the pressures vary from 1.35 to 3.6 kb. Such a temperature condition favors the gold transport as tiocomplexes. Early oxidation process brought about an increase of fO2 and magnetite formation which favored first generation of gold deposition. The mixing of ore fluid with aquocarbonic fluid and meteoric water and fluid-rock interaction, with associated phillic and sulfidation alteration reactions, caused increasing of fO2 and reduction of pH, fS2 and temperature which triggered the main gold precipitation in transtension sites of shear zone. The veining style of the São Jorge deposit, the host granitic rocks of the ore, the kinds of hydrothermal alterations, the Au(Cu-Zn-Pb-Bi) metallic association and the ore fluid of magmatic filliation, are consistent to a genetic relationship between the gold deposit and granitic magmatism (intrusion-related gold deposit). On the other hand, the structural control of the ore bodies and the occurrence of aquocarbonic fluid with higher homogenization temperature, deep-collected by the shear zone, hold up the mesozonal orogenic model. Such a characteristics support a hybrid genetic model for the São Jorge gold deposit, in which the granite supplied the ore fluid, the metals and heat to move the hydrothermal system, whereas the shear zone provided the aquocarbonic fluid, the flow paths for the fluids and the structural traps for ore deposition. Since the shear zone had affected the Yong São Jorge granite, the genetic relationship between the gold deposit and that granite, though possible, is little probable. Another more consistent possibility as magmatic source for the São Jorge ore fluid would be a younger granite, as the Maloquinha granite, 14 to 27 Ma younger, which occurs in the whole Tapajós Province and also neighborhood São Jorge area.
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Geologia estrutural, geoquímica, petrografia e geocronologia de granitóides da Região do Igarapé Gelado, norte da Província Mineral de Carajás
(Universidade Federal do Pará, 2004) BARBOSA, Jaime dos Passos de Oliveira; BARROS, Carlos Eduardo de Mesquita; http://lattes.cnpq.br/3850881348649179
To the north of the Carajás range granitoid rocks occur in an elliptical domain oriented in toWNE-ESE direction. These rocks are limited to the south and to the north by metabasalts and banded iron formations belonging to the Itacaiúnas Supergroup. The granitoids show a penetrative foliation in the body scale, striking in the WNW-ESE and E-W directions, concordant with the regional structures. Steep dipping foliations predominate but flat lying ones are locally present. Foliations are continuous, smooth, and marked by the weak to strong preferred orientation of mafic minerals and feldspars and by the flattened quartz aggregates. Stronger degrees of deformation were reached on decimeter-wide E-W mylonite zones. Discrete centimeter-wide conjugate shear bands are locally described. The structural evolution of the studied granitoids indicates emplacement synchronously to N-S compressive stress, similarly to other 2.7 Ga granitoids present in the region. Granodiorites and monzogranites predominate largely over tonalites, leucomonzogranites and syenogranites. Quartz-feldspathic pegmatites occur locally filling decimeter-wide veins. In less deformed rocks, oriented granular textures are common. Sometimes, these rocks show graphic texture accompanied of corroded amphibole crystals (honeycomb or sieve textures). Both textural evidences suggest fast crystallization controlled by undercooling conditions and emplacement at shallow levels. In moderate to strongly deformed rocks corrosion of amphibole and biotite produce symplectite textures along the surfaces parallel to foliation. In this case the corrosion is stress-controlled and it suggests deformation history of unconsolidated rocks. Two groups of granitoids can be discriminated on the basis of whole-rock chemical data: alkaline (ALK-3) and calc-alkaline (CA-2) granitoids. The rocks of both groups have moderate to high Y, Nb and Zr contents so that the calc-alkaline granitoids in some diagrams plot on the Atype field. The alkaline and the calk-alkaline rocks from the Igarapé Gelado region were most probably originated by partial melting of continental crust. The high Zr contents seem to indicate that both group of rocks were generated by high-temperature partial melting of crustal rocks. Differences of rare-earth elements patterns of the studied ALK-3 and CA-2 granitoids could reflect different depths of the source rocks. The calc-alkaline magmas, are depleted in heavy rareearth elements, compared to alkaline ones and would be produced at deeper levels. Pb-Pb (evaporation) zircon dating yielded 2.5 Ga on the low temperatures steps and 2.73 Ga on the steps of higher temperatures. The later value is considered as the minimum age to the granitoids crystallization and it is close to the ages obtained by other authors on quartz-fedspathic veins that crosscut rocks from the Igarapé-Pojuca Group. The age of 2.5 Ga could reflect some degree of perturbation on the U-Pb system. The studied granitoids belong to the syntectonic magmatism (e.g. Estrela, Planalto, Serra do Rabo, Plaquê granites) that took place in the Carajás region 2.7 Ga ago.
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Geologia, geoquímica e geocronologia do granito Serra do Rabo, província mineral de Carajás
(Universidade Federal do Pará, 2002-03-25) SARDINHA, Alex Souza; BARROS, Carlos Eduardo de Mesquita; http://lattes.cnpq.br/3850881348649179
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Geologia, geoquímica e petrologia magnética do granito paleoproterozóico redenção, se do Cráton Amazônico
(Universidade Federal do Pará, 2001-06-29) OLIVEIRA, Davis Carvalho de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
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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.
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Geologia, petrografia e geoquímica do granito anorogênico Bannach, terreno granito-Greenstone de Rio Maria, PA
(Universidade Federal do Pará, 2005-03-24) ALMEIDA, José de Arimatéia Costa de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The Bannach Granite is intrusive in Archean rocks of the Rio Maria Granite -Greenstone Terrane, located in the eastern border the Amazonian craton. This Paleoproterozoic, elliptic, anorogenic granitic batholith is composed essentially of monzogranites with alkali feldspar, quartz and plagioclase as essencial minerals; hornblende, biotite and sometimes clinopyroxene as main mafic minerals; titanite, allanite, apatite, zircon, ilmenite and magnetite as primary accessory minerals; chlorite, sericite-muscovite, carbonate ± fluorite as secondary accessory minerals. Textural and mineralogical characteristics allow to recognize eight varieties of granite: coarse-grained facies bearing amphibole, biotite and sometimes clinopyroxene [cumulatic granite (CG), biotite-amphibole-monzogranite (BAMzG), and amphibole- biotite-monzogranite (ABMzG)]; porphyritic facies with biotite [porphyritic biotite-monzogranite (PBMz)] and leucomonzogranitic fácies [coarse -grained leucomonzogranite (CLMz), early and late medium - evengrained monzogranite (EMLMz and LMLMz) and fine- evengrained monzogranite (FLMz)]. The facies distribution within the batholith is zoned, with the less evolved facies (GC and BAMzG) situated along the border of the body and the more evolved ones in its central portion (LMLMz and CLMz). The Bannach batholith is subalkaline, metaluminous to peraluminous. K 2 O/Na 2 O ratios are between 1 and 2 and FeO t /(FeO t + MgO) between 0.86 and 0.97. The different facies have similar rare earth elements (REE) patterns, being enriched in light REE, slightly depleted in heavy REE and showing a negative europium anomaly that increases from the less evolved to the more evolved facies. The several facies of the Bannach granite plot in the within -plate granite field, as defined by Pearce et al. (1984) for Phanerozoic granites, and into the field of A -type granite, as defined by Whalen et al. (1987). They also show geochemical affinities with the ferroan granites of Frost et al. (2001) and with the A2-subtype (Eby 1992). All facies of the Bannach pluton display high magnetic susceptibility (MS), decreasing regularly from the facies carrying amphibole, biotite ± clinopyroxene (GC and BAMzG) to the leucogranites (EMLMz, CLMz, LMLMz and FLMz ). The different facies of the Bannach granite evolved through fractional crystallization of ferromagnesan minerals and feldspars. The differentiation trend was in the sense: BAMzG- ABMzG-PBMz-EMLMz-CLMz-FLMz. The LMLMz facies is interpreted as a separate intrusion
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Geologia, petrografia e geoquímica do granito Bom Jardim, região de São Félix do Xingu, Província Mineral de Carajás
(Universidade Federal do Pará, 2009-05-22) PINHO, Sabrina Cristina Cordovil; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281; https://orcid.org/0000-0002-0672-3977
In the Carajás mineral province, located in the Amazonia Central geochronologic province, three important granite suites (Fig 1) were individualized on geologic, petrochemical, geochronological and isotope data in Jamon, Velho Guilherme and Serra dos Carajás (CPRM/DNPM 1999, Teixeira et al. 2002a, Dall´Agnol et al. 2005). These three suites are composed of ~1.89 to 1.86 Ga (Tab. 1) nondeformed stocks and batholiths. The absence of deformation along the massifs, the discordant character of the plutons and the presence of micrographic intergrowths suggest a high level of emplacement. All granites display characteristics of A-type granites and within-plate signature. The plutons of the Jamon suite show oxidized character, while the plutons of the Serra dos Carajás and Velho Guilherme suites are moderately reduced and reduced, respectively. In the domain of the Velho Guilherme suite, São Felix do Xingu region, the massifs Antonio Vicente, Serra da Queimada, Velho Guilherme, Mocambo, Ubim-sul and Benedita are tin (±W)-mineralized granites. The mineralization is related to evolved granitic facies affected by late to postmagmatic alteration or hosted in small bodies of greisens. The granitic rocks of the Velho Guilherme suite are dominantly hololeucocratic to leucocratic, monzogranite to syenogranite with subordinate alkali-feldspar granite. Show low contents of TiO2, Al2O3, CaO, MgO, P2O5, Sr, Ba and Cl and moderate of Hf, U and Zr. Rb, Y, F, Li, Th, Nb, Ta, Ga, and Rb/Sr, Rb/Ba, F/Cl ratios are systematically high. The Bom Jardim granite, inserted into Velho Guilherme suite, is a rounded Sn-W mineralized massif that cover ~ 400 km2, outcrops south of São Felix do Xingu city, and is intrusive in intermediate to felsic volcanic rocks of the Uatumã Group. It is dominantly constituted by isotropic, pink and medium-to coarse grained monzogranite and syenogranite. Chloritized biotite is the main primary mafic phase. Aplite dikes are common cross cutting the granite in different directions. These rocks are affected in different intensities by late- to posmagmatic alteration. Greisenized rocks containing small primary concentrations of cassiterite+wolframite, besides quartz veins with milimetre to centimetre-sized crystals of wolframite+pyrite+fluorite, were identified in pervasively altered cupolas. Magnetic Susceptibility (MS) data showed values of 5,34x10-4 SIv (minimum valor) to 9,18x10-4 SIv (maximum valor), similar to those found in the syenogranitic rocks of the Antonio Vicente pluton. Scanning Electron Microscopy (SEM) studies indicate that the Sn and W mineralization are dominantly associated with syenogranite and greisenized rocks. The zircons of the different facies of the Bom Jardim granite are characteristically enriched in Hf, Y, Th and U, and display low Zr/Hf ratios, such as zircon crystals of other specialized tin-granites of the Amazonian Craton. The obtained results demonstrate that a preliminary evaluation of the potential for Sn and W (±Nb+Ta) in evolved granites may be based on zircon compositional studies and in EDS semi-quantitative analyses obtained with a SEM. Geochemically, the rocks of the Bom Jardim granite have low contents of TiO2, MnO, MgO, CaO e P2O3. The Al2O3 is near of 13%, with RG1 displaying higher values (14%). Na2O e K2O show medium contents, except in the RG. The Fe2O3 rarely is superior to 2.0%, but it is higher in the greisenized rocks 1 (GR1), with ~7% (medium value) and greisenized rocks 2 (GR2), with ~3.7% (medium value), probably resulting from the presence of syderophyllite. Rb and Ba show inverse behavior. Rb increase in the sense of MzG-LMzG-SGRG1-RG2, with average of 294, 711,790, 874 and 1835 ppm, respectively. Ba display, in this same sense, medium contents of 670, 87, 18, 9 and 2 ppm, respectively. Sr shows similar behavior of the Ba, except in the GR, originating an increase in the Rb/Sr ratios in the sense of the more fractionated rocks. Sn and W show enrichment from less evolved to the more evolved rocks, with the GR2 displaying higher concentrations. F and Li are high in all studies facies (1400 to 3000 ppm and 15 to 134 ppm, respectively), but the higher values are found in the GR1 (21000 ppm and 698 ppm). The Rare Earth Elements (REE) show similar fractionated patterns, with negative Eu anomalies increasing from monzogranite to syenogranite rocks. The GR have similar patterns, but the GR1 are more enriched in REE than the GR2. The geochemical diagrams indicate that the fractionated crystallization was the dominant process during the magmatic evolution of the Bom Jardim granite, such as observed in others granitic bodies of the Velho Guilherme suite. Based in the obtained data and in the petrographic, geochemical and geochronological similarity with others granites of the Velho Guilherme suite, the Bom Jardim granite can be included in the context of this important Paleoproterozoic granitic suite.
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Geologia, petrografia e geoquímica dos granitóides de Canaã dos Carajás, SE do estado do Pará
(Universidade Federal do Pará, 2003-10-11) GOMES, Alan Cardek Brunelli; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
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Geologia, petrografia, geocronologia e geoquímica do Granito Anorogênico Seringa, Província Mineral de Carajás, SSE do Pará
(Universidade Federal do Pará, 2009-07-15) PAIVA JÚNIOR, Antônio Lima de; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
The Seringa Granite, with 2250 km2 of outcropping area represents the biggest anorogenic batholith of Carajás Mineral Province. It is intrusive in Archean units of the Rio Maria Granite-Greenstone Terrane, located in the southeastern of the Amazonian craton. The Seringa Granite is formed by two great petrographic groups: A) monzogranites rocks, represented by biotiteamphibole coarse-grained monzogranite, amphibole-biotite coarse-grained monzogranite; B) syenogranites rocks, represented by, porphiritic amphibole-biotite syenogranite, heterogranular leucosyenogranite, leucomicrosyenogranite, and heterogranular amphibole-biotite syenogranite. It’s formed essentially by quartz, alkali feldspar and plagioclase. Biotite and amphibole are varietal minerals and zircon, apatite, opaque, and allanyte the accessories minerals. The magnetic susceptibility (MS) data of Seringa Granite identified four populations with different magnetic characteristics, in which the highest values of MS are related to the less evolved facies and the lowest values to the syenogranitic facies, mainly leucogranites. Magnetite, ilmenite, apatite, zircon, epidote, fluorite, monazite and xenotime are accessory phases identified in Seringa Granite. The textural analysis of their oxides has distinguished five forms of ilmenite: trellis, sandwich, composite internal/external, patch and individual. Textural features suggest that titanomagnetite and individual and composite ilmenite crystallized in early magmatic stage. The Ilmenite was destabilized and partially replaced by titanite still in the magmatic stage. During the subsolidus stage, titanomagnetite was transformed by oxidation-exsolution in intergrowths of almost pure magnetite and ilmenite (sandwich, patch, and trellis ilmenite). We can infer that oxygen fugacity conditions (fO2) that prevailed during the formation of Seringa massive were possibly below the NNO buffer, but higher than the FMQ buffer. The Seringa Granite showed Pb-Pb zircon age of 1895±1 Ga, considered its crystallization age, and coincident with the other anorogenic plutons of the CMP. It is subalkaline, metaluminous to peraluminous, display K2O/Na2O ratios between 1 and 2 and FeOt/(FeOt +MgO) between 0.86 and 0.97. The patterns of REE show increase in negative europium anomalies from the less evolved facies to the more evolved facies. In these sense, it is enriched in light REE parallel to the impoverishment of heavy REE. It shows geochemical affinities with within-plate granites, ferroan granites, of the A2-subtype and oxided A-type granites. The field relations, and the petrographic and geochemistry aspects not indicate that the Seringa Granite evolved through a unique process of fractional crystallization. The Seringa Granite display more petrographic, geochemistry and magnetic susceptibility similarities with the suite Serra dos Carajás rocks, been included in that important granitoid suite.
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Geoquímica, petrogênese e evolução estrutural dos granitóides arqueanos da região de Xinguara, SE do Cráton amazônico
(Universidade Federal do Pará, 2001-05-25) LEITE, Albano Antônio da Silva; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The Xinguara region is situated in the northern sector of the Rio Maria Granite-Greenstone Terrain (RMGGT), southeastern Amazonian craton. The RMGGT is composed by greenstone belts and diversified granitoid plutons. Granitoids and gneisses, formeriy included indistinctly in the Xingu Complex, have been individualized in two new stratigraphic units: The Caracol tonalitic complex (CTc), which shows enclaves of the greenstone belts and the Água Fria trondhjemite (THaf). The Iatter is intrusive in the Sapucaia greenstone belt and in the CTc, and coeval with the Xinguara granite (Gxg). Some granodioritic bodies exposed in the Xinguara region are correlated with the Rio Maria granodiorite (GDrm). They are younger than the CTc and older than the THaf and Gxg. The dominant regional structures follow a WNW-ESE trend, observed in the south portion of the CTc and also in the comparatively younger granitoid plutons. The CTc preserves a N-S banding in its NW sector, but this structure is transposed to the WNW-ESE regional trend. The GDrm shows strongly flattened mafic enclaves, which defines a foliation; The THaf displays a magmatic banding; The Gxg pluton has an elongated shape; ali these structures follow the regional trend. The Gxg displays a weak foliation, subhorizontal at the center and dipping at high angles along the borders of the intrusion. The G1 axis of the regional stress during the intrusion of the granitoids was horizontal and trending N40E. The regional stress remained active during the submagmatic stage of the CTc evolution, as indicated by the presence of folds or boudins affecting its banding. It was responsible by the transposition to WNW-ESE of N-S structures. The stress field orientation was similar during the two phases of the Archean evolution of the region. This is suggested by the main submagmatic to subsolidus deformation structures in the GDrm, THaf, and Gxg. The changing trends of the CTc foliation suggest that the CTc was formed by domic plutons, intruded and sectionated by the younger granitic intrusions. Al-in amphibole geobarometer data suggest that the GDrm crystallized under a lithostatic pressure of —3 kbar, equivalent to a —10 km depth. The contact metamorphic effects of the Rio Maria granodiorite in the metabasaltic rocks of the Identidade greenstone belt are coherent with this data and suggest also that its emplacement was not diapiric-controlled. The variation in the intensity and orientation of the foliation in the Xinguara pluton and the deformation imprinted on its country rocks suggest its emplacement by bailooning. The emplacement of the THaf was probably controlled by diapiric processes. The CTc is a typical TTG, similar to those of the Archean trondhjemite series. Two different geochemical signatures have been identified in this granitoid on the basis of accentuated contrasts in LaN/YbN ratios. The GDrm is different of the TTG series. It follows the calc-alkaline trend and is similar to the Mg-rich granodiorites of the Sanukite Series. The THaf is geochemically similar to the CTc and by extension to the Archean TTG, but it is comparatively enriched in K2O. The Gxg is a high-K2O, strongly fractionated, calc-alkaline Archean leucogranite. Its REE pattern is indicative of a crustal origin. The dominant, high LaN/YbN ratio CTc group crystallized from a liquid probably originated from the partial melting of garnet amphibolites derived from 'normal' tholeiites. The latter should be similar in composition to the Archean metabasalts or to the metabasalts from the Identidade greenstone belt and the degree of partial fusion required would be, respectively, 25-30% and 10-15. On the other hand, the tonalites with Iow LaN/YbN ratios crystallized from a liquid derived from a garnet-free similar source. Nd isotopic data indicate a mantle source and a juvenile character for the tonalites of the first group. A tonalite sample of the second group and an enclave in the Gxg yielded negative ONd values and >3.2 Ga TDM ages. These data suggest that the tonalites of this group could derive from an older source with a longer crustal residence time. The THaf may have been generated by 5-10% partial melting of garnet amphibolites derived from metabasalts, chemically similar to the metabasalts from Identidade. The liquids of the Gxg were originated by variable degrees of partial melting of a source similar to the oldest TTG granitoids. The Archean geologic evolution of the Xinguara region occurs in two stages. The first starts in the interval of <2.95 to 2.91 Ga and is apparently similar to those of the Pilbara and Darwhar cratons. The second stage starts at 2.88 Ga and it is coincident with a sharp change in crustal behavior. At this time, the increasing thickening and stabilization of this Archean crustal segment, turned more effective the processes of plate subduction and convergence. In this tectonic context, the partial melting of an enriched mantie wedge would generate the parental magma of the GDrm and the partial fusion of garnet amphibolites derived from the subducted ocean crust would generate the THaf magma. Finally, the upward movement of the THaf and GDrm magmas would induce the melting of the TTGs in the lower crust, thus generating the granitic magmas of the Xinguara pluton.
Acesso aberto (Open Access)
Granito Serra da Queimada, Suíte Intrusiva Velho Guilherme, Província Carajás: tipologia, aspectos petrológicos e afinidades metalogenéticas.
(Universidade Federal do Pará, 2019-11-18) MELO, Lucas Maurício Condurú; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
The Serra da Queimada Granite (GSQ) is a subcircular paleoproterozoic anorogenic batholith, approximately 20 km2 in area, located north of the city of São Félix do Xingu, in the Carajás Province, southeast of the Amazonian Craton. It splits archean units of the São Félix Group and paleoproterozoic groups of the Iriri Group, Uatumã Supergroup. It is formed by three distinct petrographic facies: syenogranite biotite (BSG), monzogranite biotite (BMG) and porphyritic syenogranite (SGP), all with graphics content<10%. The frequent occurrence of spherulitic and granopyric intergrowths suggests that GSQ rocks crystallized at shallow crustal levels. Electron probe analysis showed that GSQ biotites are predominantly magmatic, ferrous and Al-enriched. Total rock geochemical analyzes showed that GSQ is peraluminous to weakly metaluminous, FeOt/(FeOt +MgO) ratios between 0.75 and 0.99 and K2O/Na2O between 0.6 and 2.3; shows geochemical affinities with intra-plate A type granites, of subtype A2, and ferrous granites, suggesting a crustal source for their origin. It has higher light rare earth element contents than heavy rare earth elements, with a sub-horizontal pattern for the latter, as well as increasing negative Eu anomalies towards the more evolved BSG facies. The geochemical data show that BSG have higher average K2O, Y, Rb, W and Sn content and lower TiO2, Fe2O3, MgO, CaO, Ba and Sr than other facies, typical characteristics of specialized granites. Crystallization temperatures based on the Zr saturation geothermometer indicated ranges between 754 °C and 870 °C, similar to other anorogenic granites in the Carajás Province. Comparative geological, petrographic, mineral chemistry and geochemical studies between the GSQ and other specialized granites belonging to the Velho Guilherme Intrusive Suite indicate that sienogranitic rocks of the GSQ show potential for mineralization in W and Sn and that it can be framed in the geological context of this important granite suite.
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Inclusões fluidas crepitadas, fluidos hipersalinos e aquo-carbônicos em quartzo associado a rochas micáceas no Granito Xinguara - Terreno Granito-Greenstone de Rio Maria, PA
(2008-03) WEBER, Marcelo Leopoldo; RONCHI, Luiz Henrique; ALTHOFF, Fernando Jacques; LEITE, Albano Antônio da Silva; DALL'AGNOL, Roberto; FUZIKAWA, Kazuo
The micaceous rocks occurring in the Xinguara Granite, Rio Maria Granite-Greenstone terrain, Pará State, Brazil, are composed of muscovite and chlorite with quartz levels intercalated forming a well developed schistosity. This schistosity is cut by quartz veins. Both quartz generations show the same aqueous, aqueous-carbonic and halite-bearing fluid inclusions either in secondary inclusions halos and trails surrounding decrepitated primary fluid inclusions or in transgranular secondary trails. A wide variation of homogenization temperatures, high salinity, necking down and the decrepitated inclusions existence indicates strong influence of post-formational alteration and reequilibration linked to the granite intrusion. These foliated rocks are metasedimentary enclaves affected by late hypersaline aqueous-carbonic granitic fluids.
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Intemperismo químico de rochas graníticas na zona bragantina nordeste do Pará
(Universidade Federal do Pará, 1980-05-13) GOULART, Antonio Taranto; RONCAL, Juan Rolando Zuleta
Profiles of residual soils derived from granitic rocks which occur in the Bragantina Region, Northeastern Pará, were studied chemically and mineralogically. These soils were developed in an ares of gentle topography and good drainage under tropical conditions with well defined "dry" and rainy seasons. The mineral composition of these soils consists essentially of quartz and with decreasing abundantes also appear kaolinite, muscovite, secondary oxides, feldspar and heavy minerals. This mineral assemblage resulted from the chemical weathering of the parent granitic rocks wh.ose original minerals were decomposed in the following sequence: biotite, feldspars, muscovite, quartz and heavy minerals. The soils are dominantly sandy from which significant amounts of kaolinite, produced during the earlier stages of weathering, were lost in consequente of the intense leaching that is favored by the high pluvial precipitation oves the region. The great stability of quartz under tropical conditions together with the intense leaching of the regolith has led to the development of texturally homogeneous soils in the Bragantina Region.
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Modelos de evolução e colocação dos grantitos paleoproterozóicos da Suíte Jamon, SE do Cráton Amazônico
(Universidade Federal do Pará, 2006-10-27) OLIVEIRA, Davis Carvalho de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The 1.88 Ga, anorogenic, A-type Jamon suite and associated dikes intruded 2.97 – 2.86 Ga-old Archean granitoids of the Rio Maria Granite-Greenstone Terrane which lies to the south of Serra dos Carajás, in the southeastern domain of the Amazon Craton, northern Brazil. Petrographic and geochemical aspects associated with magnetic susceptibility and gamma-ray spectrometry data showed that the Redenção and the northern part of Bannach plutons are normally zoned, with mingling relationships that indicate multiple magma injections in their construction. Both were formed by two magmatic pulses: (1) a first magma pulse which fractionated in situ after shallow crustal emplacement and generated a series of coarse, evengrained monzogranites with variable modal proportions of biotite and hornblende; (2) a second, slightly younger magma pulse, localised in the center of both plutons, and composed of a more evolved liquid from which even-grained leucogranites were derived. Seriated and porphyritic biotite monzogranite facies intruded the coarse (hornblende)-biotite monzogranites and formed anellar structures within the Redenção pluton. The magmatic zoning is marked by a systematic decrease in mafic mineral modal content, plagioclase/potassium feldspar and amphibole/biotite ratios, and anorthite content of plagioclase. TiO2, MgO, FeOt, CaO, P2O5, Ba, Sr, and Zr decreased, and SiO2, K2O, and Rb increased in the same fashion. Magmatic differentiation was controlled by fractionation of early crystallized phases, including amphibole±clinopyroxene, andesine to calcic oligoclase, ilmenite, magnetite, apatite, and zircon. The Jamon suite is subalkaline, metaluminous to mildly peraluminous, ferroan alkali-calcic, and displays geochemical affinities with within-plate A-type granites. The ubiquitous occurrence of magnetite and titanite as well as high magnetic susceptibility values demonstrate that granites of the Jamon suite are oxidized in character. Oxidized A-type granites have high FeOt/(FeOt+MgO), TiO2/MgO, and K2O/Na2O ratios and low CaO and Al2O3 compared to calc-alkaline granites. The oxidized character of the Jamon suite makes it more akin to the USA Mesoproterozoic magnetiteseries A-Ttype granites but differs from the reduced rapakivi granites of the Fennoscandian Shield, and Serra dos Carajás and Velho Guilherme suites of the Carajás province, probably because of different magmatic sources. The Jamon suite probably crystallized near or slightly above the nickel-nickel oxide (NNO) buffer and an Archean sanukitoid biotite-hornblende quartz diorite source was proposed for the oxidized Jamon magmas. Gravity modelling indicates that the Redenção and Bannach plutons are sheeted-like composite laccolithic intrusions, ~6 km and ~2 km thick, respectively. These plutons follow the general power law for laccolith dimensions and are similar in this respect to classical rapakivi granite plutons. Gravity data suggest that the growth of the northern part of the Bannach pluton was the result of the amalgamation of smaller sheeted-like plutons which successively intruded in sequence from northwest to southeast. Jamon suite plutons were emplaced in an extensional tectonic setting with the principal stress oriented approximately along NNE-SSW to ENE-WSW, as indicated by the occurrence of diabase and granite porphyry dike swarms, orientated WNWESE to NNW-SSE and coeval with the Jamon suite. The 1.88 Ga A-type granite plutons and stocks of Carajás are disposed along a belt defined by the general trend of the dike swarms. The inferred tabular geometry of the studied plutons can be explained by magma transport via dikes and it is supported the high contrast of viscosity between the granites and their Archean country rocks. Mechanisms responsible for emplacement of granitic plutons, and in particular of anorogenic A-type plutons, are still debated. A magnetic fabric study derived from anisotropy of magnetic susceptibility (AMS) measurements was applied to the Redenção pluton in order to understand its emplacement history. High magnetic susceptibilities (K from 1 x 10-3 SI to 54 x 10- 3 SI) indicated that magnetic fabrics are primarily carried by ferromagnetic minerals (magnetite). Low P' values and absence of intracrystalline deformation features indicated that the magnetic fabric is of magmatic origin. The magnetic fabric is well organized and characterized by concentric steep foliations associated with moderately to gently plunging lineations. The lack of a well-defined unidirectional linear fabric at pluton scale suggests the reduced or null influence of regional stresses during granite emplacement. Three stages are proposed for construction of the Redenção pluton, which reconcile the tabular shape of the intrusion with the occurrence of steep magnetic foliations: (1) ascent of magmas in vertical, northwest-striking feeder dikes and accommodation by translation along east-west-striking regional foliation planes; (2) switch from upward flow to lateral spread of magma with space for injection of successive magma pulses created by floor subsidence; and (3) in situ inflation of the magma chamber in response to the central intrusion of late facies, accompanied by evacuation of resident magmas through ring fractures.
Acesso aberto (Open Access)
Morfologia e composição de zircão de rochas ígneas do Terreno Granito-Greenstone de Rio Maria, Cráton Amazônico, através de microscopia eletrônica de varreduracatodoluminescência (MEV-CL)
(Universidade Federal do Pará, 2015-04-22) RAMALHO, Ishi Macris de Oliveira; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
Zircons of Archean TTG rocks, represented by Arco Verde Tonalite (2,97-2,93 Ga), Mogno Trondhjemite (2,97-2,96 Ga), Mariazinha Tonalite (2,92 Ga), Água Fria Trondhjemite (2,86 Ga), Rio Maria (2,87 Ga), Trairão and Grotão granodiorites and Guarantã leucogranite (2,87 Ga), beyond the São João paleoproterozoic granite (1,89 Ga), outcropping in the Rio Maria Granite-Greenstone Terrene, southeastern portion of the Amazonian Craton, were studied by cathodoluminescence images (CL) and semiquantitative analysis of EDS (Energy Dispersive Spectroscopy) in a scanning electron microscope (SEM). The internal textural features observed by CL images showed complex stories of crystallization for zircons of different groups of rocks such as: (1) euhedral crystals, strongly zoned without evident alteration and subhedral to anhedral crystals, weakly zoned and intensely altered; (2) crystals showing well defined oscillatory zoning and homogeneous crystals or with imperceptible zones, showing changes in physical and chemical conditions during crystallization; (3) crystals with Ca and U metamict enriched cores and crystals with luminescent cores resembling inherited cores; (4) zircon crystals containing several F-apatite inclusions that truncate or accompany their growth zones, indicating that apatite is a mineral phase as early as zircon in the history of crystallization of their host rocks; (5) crystals devoid of F-apatite inclusions, which could indicate compositionally different source in relation to rocks containing apatite inclusions; (6) zircons crystals with more luminescent edges than their inner portions, suggesting compositional change at the end of crystallization. Temporal and geochemically distinct granitoids were individualized and characterized in specific geochemical diagrams based on the Zr, Hf, Y, Nb and Ta content of their zircons. Zircons of the São João paleoproterozoic granite showed a distinct geochemical signature from those of TTG Archean rocks, indicating that these rocks can be individualized through composing of their zircons, even through semiquantitative analyzes of EDS. SEM-CL-EDS studies in zircons crystals are important tools in the characterization of different groups of igneous rocks and provide complementary information to petrological studies.