Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603

O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.

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Acesso aberto (Open Access)
Adsorção de molibdato em minerais de argila delaminados e amorfizados
(Universidade Federal do Pará, 2012-04-15) PEREIRA, Patricia Magalhães; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
The search for efficient methodologies to control environmental pollution, as well as the development of technologies in the fields chemical, physical and biological have been widely discussed in order to produce efficient alternatives to improve the quality of life and control of chemical pollutants (organic or inorganic) that over the years are being dumped into the environment so as inconsequential by households and industries. Thus, it is important to know about the adsorptive behavior of metals in the soil, because high concentrations of metals produce adverse effects on the environment. Molybdenum is an essential element for biological functions of plants and animals, but in high concentrations in the body can lead to bone deformities, anemia, abnormal liver and lead to death.The possibility of interaction of organic-inorganic compounds (Humic Acid, Urea andH2SO4) in sediments "in nature” from the region of Acre, was investigated with the aim of evaluating the possibility of applying these materials in adsorption processes in molybdate aqueous solutions. The natural samples used in this study have a high content of clay minerals, mainly smectite, kaolinite and low content of primary minerals such as feldspar and quartz. All samples "in nature" were characterized by XRD, XRF, FTIR, SEM and pHH2O and pHKCl. The modification with inorganic acid concentrations (0.25, 0.5, 1 and 1.5mol.L-1), temperature and contact time are important parameters in the process of delamination of the clay minerals. As the use of organic compounds such as urea and humic acid were efficient in the amorphization. The study by XRD in the modified samples show a change in the structure when H2SO4 at the concentrations used, but this fact is only observed for 15Å peak, characteristic of smectite, all other peaks showed no significant change. The synthesis of organic compounds promoted the amorphization of the smectite peak reference. Thus, as the sediment naturally has clay (smectite, kaolinite), confirmed by XRD and the presence of iron, indicating a transition to the montmorillonite nontronite, and with isomorphous substitution of iron is expected to strong interaction between the adsorption molybdate fractions modified with respect to the natural. The introduction of H+ due to the modification process with sulfuric acid promoted the replacement of calcium ions in the structure confirmed by semi-quantitative analysis performed by EDS. SEM analysis indicated the presence in natural samples cluster morphology, this fact was not observed in the modified samples, which was observed delamination and amorphization. The equilibrium conditions in the adsorption process were investigated in which it is inserted, time of 2 h and the solution pH was measured before and after adsorption. The equilibrium datawere represented by theisotherm models Langmuir, Freundlich and Sips. The adsorption process had better performance in the concentrations for samples and S10H15 S10UH. The humic acid modified samples contained higher Qmáx =3.43, values regression fit to the model obtained indicate Freundlich efficient adsorption process, the modified samples effective adsorbed molybdate anion in comparison to natural sample.
Acesso aberto (Open Access)
As águas subterrâneas de Belém e adjacências: influência da Formação Pirabas e parâmetros físico-químicos para medidas de qualidade
(Universidade Federal do Pará, 1996-04-08) SAUMA FILHO, Michel; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
In the Metropolitan Region of Belém (PA) the water supply to the population comes from springs (physiographic area of Utinga) and from a network of positional tube wells, in general, in more remote urban areas or where pumping is precarious. This work evaluates the groundwater used in the Metropolitan Region of Belém, correlating data of physical, physical-chemical and chemical parameters, in an attempt to compose an understandable picture about the quality of these waters, and to verify the influence that they suffer from the geological units in which they are located. the aquifers that preserve them are located. To carry out the work, water samples were collected in two different seasonal periods: dry and rainy. After exhaustive consultation of the files of companies, institutions and researchers, 17 tubular wells were selected, 9 in Belém, 5 in Icoaraci, 2 in Mosqueiro and 1 in Ananindeua (Annex A). The most frequent turbidity indices were between 9 and 14 units (ppm of SiO2), but some wells showed higher values (33, 41 and 71 ppm of SiO2. Only in some cases, this turbidity can be immediately correlated with the silica content obtained by chemical analysis. The most frequent color measurements are in the range from zero to 7.5 U.C., with the zero index predominating. However, some wells showed a value above 100 U.C. and others, less frequent, with indices varying between 20 and 60 U.C. The pH and electrical conductivity were quite different parameters. Thus, the highest pH and electrical conductivity indices were verified in the aquifers of the Pirabas Formation. In these cases, the pH was around 6 .4 to 7.6 and conductivity between 231 and 362 µS/cm, with a discontinuity at 87.5 µS/cm, also attributed to a well associated with the aforementioned Formation. More acidic waters (pH below 6.38 and above of 4.01) are certainly attributed to the aquifers of the Barreiras and Post-Barreiras Group. The chemical constituents, notably the contents of Ca2+, Mg2+, Na+ and K+, are consistent with the interpretation of the numerical values of pH and electrical conductivity. Without exception, the concentrations of Ca2+ are higher than those of the other cations, establishing a decreasing order according to Ca2+> Mg2+> Na+>K+, with some inversion between Na+ and Mg2+. The highest concentrations of Ca2+ (soon followed by Mg2+) result from the dissolution of carbonates present in the Pirabas limestone. In fact, confirming this assertion, the concentrations of HCO-3 are also much higher than the concentrations of Cl- and SO2-4. It is to be expected, therefore, that the dissolution of Pirabas sediments produces higher concentrations of Ca2+ and HCO-3. The silica and iron contents also discriminate such waters. In general, higher silica contents correspond to greater depths, as would be expected, taking into account the action of chemical weathering on silicate minerals. As for iron, this constitutes a differentiating parameter of the waters of the Pirabas Formation, almost always at much lower levels than the corresponding values associated with the Barreiras and Post-Barreiras aquifers, with, however, exceptions, in which appreciable indices of iron related to Pirabas sediments. It should be noted that the Pirabas Formation appears in the Metropolitan Region of Belém almost always at depths greater than 100 m, although there are records of smaller depths, but these are apparently rarer situations, as is the case with well number 3. , on the University Campus, near the Guamá River, with a depth of 76 m, and the 94 m well of the Museu Paraense Emílio Goeldi, in the central area of the city (Annex A). The exhaustive consultation of the aforementioned archives of institutions, companies and researchers led to the realization that many tubular wells installed in the urban area use water associated with the Barreiras and Post-Barreiras aquifers, where the pH values are almost always, below 6 units, and electrical conductivity measurements rarely reach 100 µS/cm. Finally, it appears that there is a need for greater investments in order to increase the prospection and use of groundwater in the region, as these, in addition to dispensing with treatment prior to distribution, are still a source of resources, not dimensioned, but of great potential.
Acesso aberto (Open Access)
A associação anortosito-mangerito-granito rapakivi (AMG) do Cinturão Guiana Central, Roraima, e suas encaixantes paleoproterozóicas: evolução estrutural, geocronologia e petrologia
(Universidade Federal do Pará, 2002-12-19) FRAGA, Lêda Maria; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
The geological mapping on a scale of 1:250,000, of an area of approximately 22,500 km2 in the central region of the state of Roraima, combined with the petrographic and microtectonic study and new geochronological, lithochemical and isotopic data, allowed the characterization of an anorthosite-mangerite association -rapakivi granite (AMG), Mesoproterozoic and its Paleoproterozoic host. Orthogneisses, foliated granitoids and charnockite rock bodies from the Serra da Prata Intrusive Suite show Pb-Pb (zircon evaporation) ages around 1.94 Ga, also inferred for the associated norites and gabbronorites. The Paleoproterozoic igneous suites were placed syn-kinematically, during Deformational Event D1, with the evolution of petroweaves indicative of high temperatures, from 600º-650ºC. These features include recrystallized feldspars by subgrain rotation, recrystallized perthitic alkali feldspars and quartz with checkerboard subgrains and have been observed in syn-plutonic dykes that cut the early-kinematic D1 fabric in the host country. The NE-NW arrangement of the Paleoproterozoic bodies was controlled by the previous structure of this sector of the Central Guiana Belt (CGC). The orthogneisses and foliated granitoids comprise two distinct suites, with lithochemical characteristics of type A granitoids, probably related to different oxidation conditions at the source. The charnockite rocks show chemical characteristics approaching those described for C-type magmatism. Sm-Nd TDM model ages between 2.19 Ga and 2.05 Ga, with ƐNd(T) values ranging from +0.68 to +2 ,47 suggested sources of limited crustal residence. The age of the orogenic events in Roraima has not yet been properly clarified, however, despite the limited data, a post-collisional positioning is proposed for the Paleoproterozoic suites studied after the accretion of transamazonian magmatic arcs. The Paleoproterozoic units constitute the basement of the Mesoproterozoic igneous suites, which comprise the anorthosites of the Repartimento unit and associated gabbronorites, the rapakivi granitoids of the Mucajaí Intrusive Suite (SIM), and the fine, porphyritic charnockites, of punctual occurrence and uncertain geochronological positioning. In SIM, three granite facies were identified (fayalite-pyroxene-quartz-mangerites to syenites; hornblende-biotite-granites; and biotite-porphyritic granites) geochemically and petrographically very similar to rapakivi granites from classical areas of Finland. The presence of fayalite in the most primitive rocks of the SIM indicates conditions of low oxygen fugacity, observed in several rapakivi granite complexes. Fine charnockites show no cpm to SIM chemical correlation. The Mesoproterozoic suites are part of an AMG (Anortosito-Mangerito-Granito rapakivi) association placed in an anorogenic environment between 1.54 and 1.53Ga. Model ages Sm-Nd, from 2.07 Ga to 2.01 Ga with ƐNd(T) values ranging from -2.37 to -1.27 suggest, for the granitoids in the association, crustal sources separate from the mantle in the Paleoproterozoic , probably during the Transamazônico. Mylonitic features related to the D2 Deformational Event, registering conditions of moderate to low temperatures (400º-450ºC), in a brittle-ductile environment, locally obliterate the igneous textures of the Mesoproterozoic units, as well as the high temperature D1 petrowebs in the Paleoproterozoic basement. These features are especially well developed in some shear zones that show dextral transpressive kinematics. The D2 event aged around 1.26 Ga relates to the K'Mudku Deformational Episode. The main D2 mylonitic zones were reactivated in the Mesozoic at shallow crustal levels and brittle conditions, during the evolution of Graben Tacutu.
Desconhecido
Biogeoquímica dos sedimentos lamosos e sua influência no padrão de distribuição da vegetação, no manguezal de Bragança, NE do Pará.
(Universidade Federal do Pará, 2009-10-30) CRUZ, Cleise Cordeiro da; LARA, Rubén José; http://lattes.cnpq.br/8695520453124286; 8695520453124286
The present study investigates the relationship between sediment-plant and biogeochemical processes involved in the development and spatial distribution of vegetation in the Bragança mangrove peninsula, exposed to macrotidal regime (spring range 4 m). Therefore, three transects were established at three different topographic levels of that peninsula being colonized by different patterns of vegetation: Transect 1 (T1) Transect 2 (T2) and herbaceous plateau (PHb). The vegetation in T1 is composed mainly by Rhizophora mangle and Avicennia germinans and it is situated in a semi-diurnal flooding regime forest. The transect T2 is less frequently flooded and is characterized by a stand of young Avicennia trees and herbaceous vegetation. In the highest part of this transect with low inundation frequency and high salt stress, the vegetation is dominated by shrubs of A. schaueriana coexisting with herbaceous vegetation of Sesuvium portulacastrum and Sporobolus virginicus. The PHB, localized in the zone with lowest inundation frequency is colonized mainly by tree species of A. schaueriana in the form of shrubs and S. portulacastrum and S. virginicus with sporadic presence of B. maritima. In these sites were performed measurements of the flooding frequency; floristic and fitossociologic inventory in mangrove forest and in the herbaceous halophyte vegetation. Also sediment cores (0-30 cm) and vegetation (leaves, stems and roots) were collected. The sediment samples were subjected to granulometrical, mineralogical and chemical (total sample) analyses, and determination of the humidity, organic matter and salinity as well as cation exchange capacity (CEC) besides determination of the total, inorganic, organic and bioavailable phosphorus. In the vegetation samples, chemical analysis of total phosphorus was performed. The variance analysis (ANOVA) One Way (Post Hoc Fisher's test) was applied to test the mean of the variables (humidity, salinity, organic matter, total-P, inorg.-P, org.-P and bioavailable-P. Discriminant analysis was used to measure the degree of influence of environmental variables (humidity, salinity, organic matter and total-P) in the discrimination of sites sampled. The correlation analysis of Pearson was used to evaluate the degree of interaction between discriminated variables with the hydrological conditions and forest structure data. Fine sediments (clay) in T1 and T2 suggest areas of slow deposition, while in the plateau high levels of sand suggest its formation on a paleodune with intense eolic reworking of sandy and tidal input of finer sediments. The main mineralogy of the sediments is composed of quartz (dominant in the sand and silt) and clay minerals: kaolinite and illite, other minerals of authigenic origin are pyrite, jarosite and vivianite and possibly smectite and k-feldspar. The main mineralogical and chemical composition of major and trace elements indicate the influence of sediments and soils of the Barreiras Formation on the genesis of sediments mangroves and marine influence in their chemical composition. In T1 (the more flooded sector), the dominant species is R. Mangle, while in T2 (less flooded zone) the Avicennia genus is predominant. In the herbaceous plateau the dominance of the S. portulacastrum species, is five times higher than that of S. virginicus, indicating that Sesuvium has greater ability to survive in environments with salt stress. The flooding gradient results in highly significant positive correlation with humidity. This trend is reflected in the tree height, volume and basal area correlated significantly with sediment phosphorus availability in T1 and CEC in T2. The results of Discriminant Analysis show that in T1 the humidity is the variable that most contributes in the discrimination of (Rhizophora and Mixed) forest of the Avicennia forest, while organic matter (OM) discriminated the Mixed forests and Rhizophora forests. In T2, the humidity, total-P and salinity are the variables that most contribute to the discrimination of sites in this transect. In the profiles, along the plain, the total-P and organic mater were the most important variables for discrimination of T1, T2 and PHb. The distribution of vegetation reflects different ecophysiological responses to environmental gradients. Therefore, the combination of organic matter, salinity, and phosphorus and, the high cation exchange capacity of sediments represent a significant role in the colonization of vegetation in the peninsula of Bragança.
Desconhecido
Caracterização geológica da suíte ofiolítica Serra do Tapa, SE do Pará – Cinturão Araguaia
(Universidade Federal do Pará, 2015-04-30) BARROS, Luisa Dias; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
In northern Araguaia Belt (CA) along its low-grade metamorphic domain, the region known as Serra do Tapa, between the municipalities of Sapucaia and Xinguara, SE Para exposes one of the largest CA ophiolite bodies interpreted as fragment of oceanic lithosphere the Araguaia basin in Neoproterozoic. The Suite Ophiolitic Serra do Tapa (SOST), denominade in this work, is a set of elongated bodies with a length of 48 km with preferential orientation in the direction N-S. It represents a dismembered ophiolitic sequence comprising serpentinized peridotites, massive and pillow basalts, volcanossedimentary rocks, iron formation and cherts. All this set embedded through thrust zones in the metasedimentary rocks of low metamorphic grade of Formation Couto Magalhães. The serpentinized peridotites have dark or light green, coarse-grained and represent the basal portion of the stratigraphic sequence suite. Originally, the peridotites were probably the harzburgite and dunites type. The harzburgites have protogranular texture, with a marked presence of pseudomorphic textures bastite type and mesh, which result from orthopyroxene transformations; and olivine to lizardite, respectively. The dunites have mesh predominant texture, with the presence of fine chromite grains dispersed in the matrix composed of serpentine (lizardite). The volcanic unit of suite represented by massive basalt submarine flows and pillow structures. The basalts occur as homogeneous flows, massive and in the upper portions feature marked for pillow structure, and locally, breccia flow surface (hyaloclastites). The pillows have a zoning, where in the core consists of massive basalt greenish brown color, aphanitic with intersertal texture composed of crystals of plagioclase, volcanic glass and Clinopyroxene. At the edge zone are present glassy basalts of yellowish green color, aphanitics and quenching textures ultrafast as spherulites, and radial acicular crystals of plagioclase, textures type "swallowtail" and hollow sections. The hyaloclastites occur in the outer zone of the pillow and represent breccias surfaces basaltic. Finally, basalt glass is dark green color of the surface flows (interpillow zone). The volcanossedimentary interface sequence is the interaction between the basalt flows and pelitic sedimentary rocks. The tuffaceous mudstone consists of a pelitic matrix with lytic fragments of metabasalt stretched and broken. The sedimentary portion of the suite consists of iron formation and cherts and represent the chemical sedimentation records in deep-sea ocean environment, is the upper portion of this ophiolitic suite. Another important feature is the presence of sinistral strike-slip shear zones and dextral of kilometric extensions with preferential orientation NE-SW and EW. All structures truncated by normal faults of NW-SE direction. The rocks of Formation Couto Magalhães evidence of metamorphism is most obvious in slates and phyllites (sericite and chlorite formation) in serpentinized peridotites occurs generation of non-superposition serpentine pseudomorphs of pseudomorphs, the massive basalts, the metamorphic association is defined by ab + Tr act + Cl + Ep ± Stp; the paragenesis of these rocks indicate metamorphic transformation in greenschist facies low. For lithochemical studies were prioritized portions of the core of the pillow, which remained in many cases, the protected metasomatic transformations. Divergent data in some samples can be explained because they are samples closest to the edges of the pillows, which suffered intense transformation due to oceanic metamorphism. Geochemically, the basalts show subalkaline nature, tholeiitic compatible with the MORB type. Sr negative anomalies may indicate plagioclase retention during partial melting events from depleted mantle source. The ETR diagram shows slightly depleted behaviors of LREE and enriched in heavy REE and smooth Eu anomaly; and this pattern confirmed the reasons (La / Yb) N and (La / Sm) N <1 magmas also point to the N-MORB type. The evolution of the suite is on the development of oceanic Araguaia Basin with the generation of an old oceanic lithosphere to rise and perhaps upper mantle exposure, volcanism forming the deep ocean substrate and sedimentation (tuffaceous mudstone, banded iron formation and cherts). Later detachment processes of the substrate crust / mantle led to the tectonic inversion of the sequence, leading to compressional tectonic phase, which led to obduction of ophiolite bodies, generating a late thrust and transcurrent system with movement toward the Amazonia Craton, segmented the ophiolite bodies and mixing them with rocks Couto Magalhães Formation accompanied by regional metamorphism of greenschist facies low.
Desconhecido
Caracterização geológica, petrográfica e geoquímica de Granitos Arqueanos da Folha Marajoara, Terreno Granito-Greenstone de Rio Maria Sudeste do Pará
(Universidade Federal do Pará, 2009-07-08) DIAS, Samantha Barriga; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
During geological mapping in the Marajoara Sheet, located in the south portion of Rio Maria Granite-greenstone Terrane, southeastern of Amazonian Craton, three groups of Archean granites were distinguished: The Guarantã Suite, the Rancho de Deus Granite and Leucogranitic stocks. The first group is composed of three plutons, named Guarantã Granite (Gg), Azulona Granodiorite (GDaz) and Trairão Granodiorite (GDt), which are intrusive in the Arco Verde Tonalite and were assembled in the Guarantã Suite. The Rancho de Deus Granite is an oval stock, in contact with the Rio Maria Granodiorite and the Guarantã Granite, the latter contact being controlled by a regional shear zone. The third group is formed by small leucogranite bodies, intrusive in the Arco Verde Tonalite and Rio Maria Granodiorite. The epidote-biotite granodiorites to monzogranites of the Guarantã Suite display EW to NW-SE foliation and a porphyritic texture, with coarse alkali feldspar phenocrysts in a fine- to medium-grained matrix. The Rancho de Deus Granite is composed of hornblende-biotite monzogranites with a discrete foliation and porphyritic texture, displaying coarse alkali feldspar phenocrysts in a medium, even-grained matrix. The leucogranites are equigranular, medium-grained rocks. Geochemical data show that the Guarantã Suite and the leucogranites are dominantly peraluminous rocks, whereas the Rancho de Deus rocks vary from metaluminous to peraluminous granites. The three granite groups show strong geochemical contrasts. The Guarantã Suite is enriched in Al2O3, CaO, Na2O, Ba, Sr and Ga and impoverished in Fe2O3, K2O, MgO, Rb and Th compared to the Rancho de Deus Granite. On the other hand, the leucogranites are enriched in SiO2 and K2O and impoverished in Fe2O3, MgO, Na2O, CaO, P2O5, Ba, Sr, Zr, compared to the other two groups. The three groups exhibit moderate to strong HREE fractionation; the Guarantã Suite granites show only discrete negative or positive europium anomalies or are devoid of it. The europium anomalies in the Rancho de Deus Granite are discrete but always negative and those of the leucogranites are also negative but more important. The Rancho de Deus Granite and the Guarantã Suite rocks are similar geochemically to the Archean CA2 calcalkaline granites. However, the geochemical contrasts between these two groups cannot be explained by magmatic differentiation processes, because their rocks have similar SiO2 contents and display distinct trends in geochemical plots. Hence, the hypothesis of a genetic linking between these two granites is discarded and it is assumed that their magmas derived from different sources or evolved by different magmatic processes or both. A comparison between the three studied granite groups and similar Archean rocks of the RMGGR has shown that the Guarantã Suite rocks are similar to the granodiorites and monzogranites found in small satellite stocks associated with the Xinguara Granite pluton and with the Guarantã Granite, as originally defined by Althoff (1996). The Rancho de Deus Granite is similar to the Rio Maria Granodiorite and other rocks of the sanukitoid series. Finally, the leucogranites display petrographic and geochemical affinity with the Mata Surrão Granite. The large area of exposition and volume of the Guarantã Suite demonstrated that this variety of leucogranites was relevant in the evolution of the RMGGT and that, besides the Xinguara and Mata Surrão potassic calc-alkaline leucogranites, they should be considered as an important event of granitic magmatism in the RMGGT. This suite is better exposed in the Marajoara area, but similar rocks, alike those of the satellite stocks of the Xinguara pluton, were previously described and other similar rocks were probably mixed with the mentioned leucogranites in the past.
Desconhecido
Caracterização petrográfica, geoquímica e geocronológica U-PB das rochas de alto grau metamórfico do Complexo Tartarugal Grande, sudeste do Escudo das Guianas, Amapá
(Universidade Federal do Pará, 2016-10-26) PAIVA, Hanna Paula Sales; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
The Tartarugal Grande Complex is represented by a high rock metamorphic association degree of Paleoproterozoic with Archean relics, which occurs on the northern edge of the Amapá Block, in the context of Maroni-Itacaiúnas Province, southeast of the Guyana Shield. In this region, the Tartarugal Grande Complex meets gneiss and granulite rocks, dominated enderbitic and charnockitics types, forming elongated rocks and marked by lineament NW-SE direction, characterized as transcurrent and thrust shear zones. This unit is formed by an intricate combination of high-grade metamorphic rocks and this study aimed to characterize these rocks petrographically, geochemically and geochronology discussing the processes in this metamorphic terrain. Petrographic analyzes identified five types of rocks classified as charnockitic granulite, charnoenderbitic granulite, enderbitic granulite, mafic granulite and leucogneisses Migmatization features as neossomes also present in felsic granulites (charnockitics, enderbitics and charnoenderbitics) and gneisses. The felsic granulites are the dominant rocks in the area, while the mafic granulites occur as smaller rocks, metric dimensions, embedded in other granulites and gneisses. The leucognaisses are commonly associated with enderbitic/charnockitic granulites, showing sudden contacts with these rock types. The lithogeochemical studies in these rocks indicated that the Tartarugal Grande Complex predominance of acid rock with silica content between 61 and 75%, and peraluminous, due to the presence of minerals such as biotite, garnet and cordierite. The mafic granulites are dominantly basic types (SiO2 between 48 and 55%) with high Fe2O3 levels (12 to 26%), MgO (5 to 19%) and CaO (2 to 12%). In geochemical classification diagrams felsic granulites and leucognaisses are located in granite field, while the mafic granulites plots in gabbro field. In AFM diagram, the felsic granulites have characteristics of collisional calc-alkaline suite and mafic granulites are basaltic types of tholeiitic suite. In the multi-element diagrams felsic granulites out more significant anomalies of Ti and P, in addition to the strong negative anomaly of Nb, characteristic of subduction environments. The mafic granulites shows, mostly signed with sub-horizontal pattern. For the rare earth elements (REEs), felsic granulites at moderate enrichment of light REEs, for heavy REEs with low Eu anomalies (ratio Eu/Eu* = 0.19 to 5.51). The mafic granulites had a lower degree of fractionation and recorded insignificant Eu anomalies (ratio Eu/Eu* = 0.44 to 1.07). The leucogneisses shows very similar to the felsic granulites signature, but have different genesis. In the discrimination diagrams of tectonic environments, it was established magmatic arc environment related to the subduction zone. U-Pb geochronological analyses in situ zircon crystals by LA-ICP-MS done in charnoenderbitic granulite, enderbitic granulite, garnet–biotite leucogneisse and charnockitic granulite, provided average ages of 2045 ± 14 Ma, 2084 ± 7.9 Ma, 2617 ± 25 Ma and 2671 ± 10 Ma respectively. These results represent the formation age of the protoliths of these rocks. Ages obtained by other studies by Sm-Nd whole rock-garnet between 2.02 and 1.98 Ga indicate a high grade metamorphic event near the age placement of plutons. The parageneses characteristics of the rocks found in the search area are represented by: mesopertitic Mc + Qtz + Pl + Opx + Bt (charnockitic granulite); Pl + Qtz + mesopertitic Mc + Opx ± Bt (charnoenderbitic granulite); Pl + Qtz + mesopertitic Mc + Opx + Bt ± Cpx ± Hbl (enderbitic granulite); Pl (An60) + Opx + Cpx + Hbl (mafic granulite) and; Qtz + Mc + Pl ± Bt ± Grt ± Crd (leucogneisses) and these associations indicate that the rocks was subjected to conditions of regional metamorphic granulite facies in temperature conditions between 780 and 850°C and pressure between 5 and 7 kbar. Not extensive meltings (anatexis) are also common in the area where masses of sienogranitics compositions originated under high temperature conditions from granulites and gneisses. In addition, characteristics indicative of cooling were found in these rocks, such as partial or total replacement of pyroxene by biotite and/or hornblende, garnet by biotite and cordierite by pinit. Thus, in accordance with results of studies already developed in the area and indicated by datings performed in this present study, it was concluded that the Tartarugal Grande Complex comprises rocks that were involved during magmatic events in Neoarchean and Rhyacian, followed by high-grade metamorphism in Paleoproterozoic end and related thermo-tectonic Transamazonian event. This event deformed pre-existing types and rebalanced minerals rocks, resulting in a complex association of granulites and gneisses with different ages, origins and deformation intensities.
Desconhecido
Caracterização petrográfica, mineralógica e litoquímica das rochas vulcânicas do Gráben Jaibaras-CE
(Universidade Federal do Pará, 2000-05-03) NASCIMENTO, Rosemery da Silva; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502; https://orcid.org/0000-0003-1877-9756
The studied area is located in the northwest region of Ceará, in the domain of the Borborema Province and comprises two sectors along the Gráben Jaibaras. The study focused on the Parapuí Suite, which comprises a succession of volcanic rocks related to the Neoproterozoic. Three main groups of rocks were identified in the suite, including alkaline basalts (andesine-basalts, ilmenite-basalts and trachybasalts), rhyolites and volcanoclastic rocks that occur interspersed with the arcosian sandstones of the Jaibaras Group. The alkaline basalts, the most abundant types in the suite, occur in successions of extensive flows of massive and amygdaloid lavas, comprising holocrystalline or hypovitreous variations with porphyritic, serial or aphyric textures. Features indicative of very rapid cooling with acicular, dovetail, skeletal and resorption crystals, embedded in glass, demarcate interfaces between the various levels of effusions. The main minerals comprise labradorite with variations for andesine, titanoaugite and subordinately alkali-feldspar, olivine, ilmenite, pyrite, titanite and apatite. The minerals present in the tonsils are carbonates, zeolites, quartz, epidote, chlorite and prehnite. Chemically, basalts are characterized by high levels of alkalis, TiO2 and P2O5, and rare earth elements with an inclined pattern, showing enrichment in light REE, small negative anomaly of europium and moderate and high (La/Lu)N ratio. In the classification diagrams they are located in the field of alkaline basalts and/or in the interphase between tholeiitic and alkaline basalts. In the spiderograms of trace elements and rare earths, the various analyzed samples present a similar geochemical signature, despite the transformations in low metamorphic degree existing in these rocks, which reveals a compositional homogeneity of this magmatism. Interpretations of tectonic paleoenvironment suggest that it corresponds to continental intraplate magmatism. The rhyolites represent little expressive and rare flows in the suite, constituting porphyritic rocks in which bipyramidal quartz phenocrysts stand out, corroded, immersed in a felsitic, spherulitic microcrystalline matrix and with fluid structures. Chemically, they are rich in SiO2 and alkalis, with low Na2O/K2O ratios. The behavior of minor and trace elements in the spiderograms highlights that the geochemical signatures of these rocks contrast with the basalts. The Parapuí Suite was established through intense volcanism during the extensional tectonic installation of the Jaibaras Basin in the rift stage. It represents an intracontinental alkaline magnetism with a bimodal contribution fundamentally of a basaltic and alkaline rhyolitic nature, in a subaerial environment with effusions and explosions.
Desconhecido
Charnoquitos de Ourilândia do Norte (PA): geologia, natureza e implicações tectônicas para a Província Carajás.
(Universidade Federal do Pará, 2019-10-02) FELIX, Williamy Queiroz; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The granite-charnockite association from Carajás Province is spatially associated with gabbronorites, which intrude Mesoarchean granitoids and form a NE-SW elongated pluton with subordinate lenses E-W oriented showing subvertical (70-80°) foliation. They consist of leucocratic rocks (M' = 21.1 - 32.9) with well-preserved magmatic textures and medium- to coarse-grained. The main mafic phases are pyroxene [enstatite/ferrosilite and augite/diopside (Wo1En66Fs33 to Wo49En38Fs14)], amphibole [hornblende (0.88 ≥ Mg/(Mg+Fe2+) ≤ 0.43)], and biotite [0.68 ≥ Fe/(Fe + Mg) ≥ 0.31]. These rocks are considered syntectonic plutons emplaced in a postcollisional setting, which underwent dynamic recrystallization controlled by subgrain rotation (SGR; 400-450 °C) in a sinistral transpressive deformational regime driven by pure shear. The granite-charnockite association and gabbronorite present very similar geochemical behavior: magnesian affinity [whole-rock 0.8 ≥ FeOt/(FeOt+MgO) ≤ 0.5], calc-alkaline and high-K calcic-alkaline trends and metaluminous character. Magma ascent and emplacement are reconstructed as a singlestage process with decreasing temperatures. Crystallization temperatures range from 1100 to ~700 °C for pyroxenes, and 809 to 713 °C for amphiboles. Calculated crystallization pressures were 190 to 310 MPa resulting in crystallization depths of 7.0 to 10.5 km. Observed mineral assemblages and compositions of the main mafic minerals imply crystallization under relatively oxidizing conditions (NNO -9.8 to -12.6). H2O contents ranging from 4.1 to 6.5 wt% and indicates that water played an important role in the magmatic evolution of the studied rocks. Hydration was responsible for differences in the modal contents of monzogranite varieties. Gabbronorites were probably formed by partial melting of depleted mantle source (low HFSE), and orthopyroxene-bearing granitoids originated through fractional crystallization from magma similar in composition to gabbronorite.
Desconhecido
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
Desconhecido
Estudos isotópicos de U-Pb, Lu–Hf e δ18o em zircão: implicações para a petrogênese dos granitos tipo-A paleoproterozóicos da província Carajás – Cráton Amazônico
(Universidade Federal do Pará, 2018-04-05) TEIXEIRA, Mayara Fraeda Barbosa; SANTOS, João Orestes Schneider; http://lattes.cnpq.br/5516771589110657; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
In ca. 1880 Ma an extensive magmatic event generated A-type granites with rapakivi affinity in the Amazonian Craton, especially in the Carajás Province. In this Province these granites are grouped into three main suites according to mineralogy, geochemistry, and state of oxidation of their magmas – Jamon, Velho Guilherme, and Serra dos Carajás – and include also the Gogó da Onça, Seringa, São João, Gradaús, and Rio Branco plutons. The Gogó da Onça Granite (GOG) comprise a stock composed by biotite-amphibole granodiorite, biotiteamphibole monzogranite and amphibole-biotite syenogranite. The GGO crosscut discordantly the Archean country rocks and are not foliated. All Gogó da Onça Granite varieties are metaluminous, ferroan A2-subtype granites with reduced character. The major and trace element behavior suggests that its different facies are related by fractional crystallization. Zircon and titanite U–Pb SHRIMP ages show that the pluton crystallized at ~1880-1870 Ma. This is more akin to the Serra dos Carajás Suite and to the Seringa and São João granites of Carajás and to the Mesoproterozoic Sherman granite of USA and the Paleoproterozoic Suomenniemi Batholith of Finland. New U-Pb SHRIMP data for the Serra dos Carajás, Velho Guilherme and Jamon Suite and for Seringa and São João Granite show that these plutons crystallized between 1880 Ma to 1857 Ma. Some granites of the Velho Guilherme and Jamon suites and of the Seringa Granite presented 1920 to 1900 m. y. old zircon and titanite crystals interpreted here as antecrysts from an earlier pulse of magma that were incorporated in the main later pulse of 1880 Ma. We also obtained ages of 1865 Ma to 1857 Ma in the leucogranite facies of the Redenção and Bannach plutons, which indicate that the leucogranites of these plutons are younger than their ~1880 Ma old granites and were generated by independent magma pulses that are not cogenetic with the less evolved facies of the respective plutons. Besides it, an age of 1732 ± 6 Ma obtained in the leucogranite facies of the Antônio Vicente pluton of the Velho Guilherme Suite that could represent a magmatic event in the Xingu Region not yet reported or, eventually, could correspond to an isolate hydrothermal event that allowed the growth of zircons. This ranites have been also analysed by Lu–Hf and Oxygen isotopes and few granites also by Nd isotopes. Zircons from all the granites have remarkably restricted initial 176Hf/177Hf (0.281156 and 0.281384) and strongly negative εHf(t) values ranging from –9 to -18, and δ18O fairly homogeneous varying from 5.50‰ to 7.00‰. Small differences were observed internally in the plutons or between them. The ƐHf(t) values of the analysed plutons are strongly negative and similar to Nd isotopic data. The Serra dos Carajás Suite has ƐHf(t) values of -14 to -15.5, the Jamon Suite of -9.5 to -15 and values of -12 to -15 for the Velho Guilherme Suite, while São João, Seringa and Gogó da Onça granites have stronger negative values (ƐHf(t)= -12 to -18). Crustal model ages indicate a Paleoarchean source (3.3 Ga to 3.6 Ga) with a minor contribution from Mesoarchean (3.0 Ga to 3.2 Ga) melts for these granites. This model ages are older than the exposed Archean country rocks of the Orosirian granites of the Carajás Province and more investigation is needed to verify the real existence of that older Archean crust. The studied samples have Hf– O isotopic compositions that overlap within error, and evidence of contamination (crustal assimilation or mixing) of a mantle-derived magma cannot be seen. These plutons crystallized from magmas generated by melting of pre-existing igneous rocks with possibly in the Velho Guilherme Suite a minor contribution from a supracrustal (metasedimentary) component. The Nd, Hf, and O isotope compositions of the Paleoproterozoic granites of Carajás Province clearly attest to an igneous ancient crustal source in the origin of their magmas. The differences observed can result for contrasts in the crustal domains of the Carajás Province that were the source of the granites or of local contamination processes.
Acesso aberto (Open Access)
Evolução magmático-hidrotermal do granito mocambo, Província Estanífera do Sul do Pará: um estudo morfológico e composicional de quartzo e cassiterita
(Universidade Federal do Pará, 2018-10-02) BARROS NETO, Rubem Santa Brígida; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
The present research deals with the morphological, compositional and textural aspects of quartz and cassiterite crystals of the Mocambo Granite (MG) and of associated greisens bodies, belonging to the Velho Guilherme Intrusive Suite, Carajás Province, and its relation with the tin mineralization. The study was performed with the aid of scanning electron microscope (SEM), using catodoluminescence (CL) images, semiquantitative analyzes by energy dispersive spectroscopy (EDS) and by electronic microprobe (EM) analyzes. Different facies and greisenized rocks of the MG were studied and it was possible to identify five types of quartz, called Qz1, Qz2, Qz3, Qz4 and Qz5. The Qz1, considered the most earlier type and of magmatic origin, can be found in all facies, being less frequent in the greisens. It appears as anhedral phenocrysts to luminescent sub-rounded (light gray), with varying degree of fracturing, as well as fine-to medium-grained crystals dispersed in the groundmass. Luminescent nuclei with alternating or reasorbed alternating light-dark zonations are common. Qz2 is posterior to Qz1 and not luminescent (dark gray); is present in all facies, but is rare in the greisen. It usually occurs as irregular discontinuous stains or filling fractures and shafts that section the Qz1, suggesting a process of intense replacement. The Qz3 does not show luminescence. It occurs in almost all facies filling a fracture that cuts Qz1 and Qz2. The Qz4 is present in the most evolved and intensely altered rocks, in the greisen and in veins or interstitial cavities, usully associated with cassiterite crystals. It is represented by euhedral, medium-greined, slightly fractured crystals, with well-defined light-dark zoning and variable thickness. Qz5 occurs sectioning and forming irregular spots on Qz4, being associated generally with wolframite or wolframite + cassiterite in quartz veins. They are slightly fractured, luminescent, meduium-to-coarse greined anhedral crystals. Qz1 and Qz2 from porphyritic syenogranite to monzogranite facies show high Ti concentration (9.5 - 104 ppm) and low Al (10 - 149 ppm). Qz1, Qz2 and Qz3 crystals from the aplitic alkali-feldspar granite facies presented slightly lower Ti contents (5 - 87 ppm) in comparison to SGMP quartz values and Al values that reach 2065 ppm. In the Qz1, Qz2 and Qz3 of the greisenized rocks, the Ti presented lower contents (0.0 and 62 ppm) and variable Al content (0 - 167 ppm). In the Qz4 crystals of the mineralized greisenized rocks in cassiterite, the Ti did not exceed 20 ppm, while Al presented strong enrichment, exceeding 3000 ppm. In the mineralized quartz veins in wolframite or wolframite + cassiterite, consisting mainly of Qz5, the Ti and Al concentrations presented generally low values, with maximum contents of 7 and 77 ppm, respectively. The cassiterite is occur as anhedral to subhedral fine-to coarse-grained crystals, anhedral to subhedral, associated to chlorite, muscovite, fengite and siderophyllite in gresenizeds rocks or commonly included in wolframite crystals in quatz veins. Shows light brown to reddish color and high colors of interference. More developed crystals show concentric zoning. Analyzes carried throug ME showed that in addition to Sn, cassiterites have lower concentrations of Fe, Ti, W, Nb and Mn traces. The concentrations of Fe, Nb, Ti and W are higher in the darker spots, while Sn shows higher purity in the lighter parts of the crystals. Cassiterites associated with Qz5 (hydrothermal) are often included in wolframite crystals or are partially substituted by it. This study showed that quartz was an excellent marker of the magmatic evolution and late alteration resulting from hydrothermal processes that operated in the Mocambo granite. It was possible to distinguish one magmatic and four hydrothermal types of quartz. The CL images indicate that the tin mineralization is present in the most evolved rocks and hydrothermally altered as in greisenized rocks and quartz veins, where the cassiterite is associated with Qz4 or Qz5 + wolframite. Qz5 suggests a possible mineralizing hydrothermal event of wolframite, subsequent to the origin of the cassiterite associated with Qz4.
Acesso aberto (Open Access)
Evolução petrológica e estrutural do gnaisse estrela, Curionópolis, PA
(Universidade Federal do Pará, 1991-12-18) BARROS, Carlos Eduardo de Mesquita; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
Acesso aberto (Open Access)
Fácies deposicionais, estratigrafia e aspectos estruturais da cobertura sedimentar paleoproterozoica na serra do Tepequém, Escudo das Guianas, Estado de Roraima
(Universidade Federal do Pará, 2010-12-09) FERNANDES FILHO, Lucindo Antunes; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553; 5463384509941553
In the northern South America, occurs the largest continuous exposure of Paleoproterozoic sedimentary deposits related to the Roraima Supergroup, forming the Pacaraima Block with 73,000 km2. This siliciclastic succession of more than 2 km thick is inserted in the Guyana Shield, northern Amazon Craton, extending from in the border of Brazil, Venezuela, Guyana and Suriname. Near of the Pacaraima Block occur isolated mountains with little-known siliciclastic successions of the faciologic and stratigraphic point view, which does not allow a better correlation with the Roraima Supergroup and, consequently, hinders the paleogeographic and paleoenvironmental reconstitution of the Paleoproterozoic in this part of Amazonia. Outcrop-based stratigraphic and facies studies in the Serra do Tepequém and Uiramutã region, State of Roraima, northern Brazil, allowed redefined and redescribed the lower unit of Roraima Supergroup as Arai Group. The Arai Group of approximately 400 m thick overlies acid volcanic rocks of the Surumu Group, is covered by siliciclastic deposits of the Suapi Group and has been subdivided into two formations. The lower one, similar in both areas, generally consists of polymictic conglomerates, cross-bedded sandstones with microplacers of hematite, and subordinate mudstones interpreted as braided stream deposits. In contrast, the upper formation, in the Uiramutã region, is composed of silty fine-grained sandstones with medium-scale trough cross bedding and convolute lamination deposited in a more distal braided stream environment. This unit, in the Serra do Tepequém region, consists of fine to medium-grained cross-bedded sandstones with mudstones, sandstone/mudstone rhythmites and subordinate conglomerates and breccias interpreted as coastal, tide-influenced deposits. The top of the Arai Group is marked by an expressive unconformity covered with diamond-bearing conglomerates and pebbly sandstones of the basal Suapi Group, interpreted as braided stream deposits. This study confirms the previous interpretation of a big braided stream system migrating to southwest in the central part of the Guyana Shield. In addition it could be shown that the fluvial system in its distal part (Serra do Tepequém) was influenced by tidal processes. The stratigraphy of the Arai Group has established the basis for a regional correlation included deposits of isolated occurrences in the Guyana Shield and points to the presence of a large intracratonic Paleoproterozoic basin connected to the open sea. The structural framework of Serra do Tepequém indicates that major sinistral oblique, normal and reverse NE-SW fault zones bound domains whose bedding dips mainly towards SE and NW. Regional scale forced folds are represented by kilometer scale kink bands and chevron folds compatible with upper-to-middle crustal level. These findings differ from previous regional models based on folding under ductile conditions related to collisional tectonics and evidence the importance of Guiana Shield early basement structures, reactivated probably during the K'Mudku event (~ 1.2 Ga).
Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
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
Acesso aberto (Open Access)
Geologia e geoquímica dos granitóides Arqueanos da área de Bannach (PA): uma reavaliação das áreas de ocorrência do trondhjemito mogno e granodiorito Rio Maria
(Universidade Federal do Pará, 2018-08-21) MACHADO, Jean Ricardo Mesquita; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The Bannach area is located in the center-west of Rio Maria Domain, Carajás Province, Amazonian craton. Based on field relationships, petrography and geochemical behavior, it was possible to identify six varieties that was divided into two groups: (i) high silica and low Mg group, represented by trondhjemitic rocks associated with mogno Trondhjemite (TdhMg), leucogranodiorites and fine grained granitoids and (ii) low silica and high Mg groups, represented by biotite granodiorites, amphibole bearing tonalites and biotite tonalites (enclaves). The trondhjemites, leucogranodiorites are the most extensive batholiths of the region, covering approximately 90% of the work area, presenting medium-to-coarse heterogranular texture and E-W to NW-SE ductile deformation features. The biotite granodiorites occur as a small stock in the north-east, being formed by more enriched in mafic minerals rocks than the predominant granodioritic variety. The amphibole bearing tonalites (± quartz diorites) is emplaced along shear zones that intersect the central portion of the area, being more deformed than the other rocks and the only amphibole bearing granitoid. In smaller proportions, the biotite tonalites represent mega-enclaves of the trondhjemitic rocks, whereas the fine granitoids intersect the other rocks of the region. These varieties are divided into two groups. Geochemically, the group of high silica (SiO2> 70%) presents high levels of Al2O3, CaO and Na2O (especially leucogranodiorites) in detriment of Fe2O3, MgO, Ni and Cr. Moreover, these varieties have high La/Yb and Gd/Er ratios, discrete or absent Eu negative anomalies, and strongly fractionated REE patterns. On the other hand, the low silica granitoids present high content of Fe2O3, MgO, Ni and Y, emphasizing the high K- Ba-Sr content of the biotite granodiorites in relation to the other granitoids in the area, in addition to their moderate to high La/Yb ratios, while the other low silica granitoids present low La/Yb ratios because of the high HREE content, which provides a sub-horizontal REE pattern. These differences trace back distinct formation processes for Bannach granitoids. Although the formation of trondhjemites and leucogranodiorites occurs in the garnet stability zone, its chemical differences go back to sensible differences in its magma. The origin of the trondhjemites is associated with the partial melt of garnet amphibolite, under high pressure conditions in a subduction environment. The leucogranodiorites, due to their higher sodium enrichment, Ba and Sr, have their compositional control associated to different degrees of melting of basalt under different pressure levels and by a source richer in subducted sediments of the oceanic crust to produce magmas of similar composition to the leucogranodiorite. Therefore, it is assumed that these rocks would have originated by the fusion of enriched tholeiite basalts installed below an older TTG crust that would have been assimilated by these melts. The geochemical aspects, such as the high LILE content and even high presence of mantle affinity elements (Mg, Ni and Cr) of the biotite granodiorites and amphibole bearing tonalites may denounce their affinities with the rocks of the Sanukitoid suite of Rio Maria. The ambiguous geochemical character of the biotite granodiorites associated with the highest SiO2 content when compared to the quartz diorites, as well as their higher levels of Rb and Ba, Sr, Y and the La/Y and Sr/Y ratios indicate a more evolved and conditions of formation in higher pressure and that has felsic parent magmas, as well as a mafic component acting in its origin, approaching the Closepet-type granites. In this way, these compositional affinities indicate a strong petrogenetic analogy, with an origin from an enriched mantle or even from a mafic source of high-K. On the other hand, the less evolved character of the amphibole tonalites, as well as the low La/Yb and Sr/Y ratios indicate that these have a higher mantle affinity and that formed at low depths. It is assumed that the origin of these rocks would have been from a metassomatized mantle by slab fluids in a subduction environment.
Acesso aberto (Open Access)
Geologia e Geoquímica dos Granitoides Mesoarqueanos da Porção Noroeste do Domínio Rio Maria da Província Carajás: individualização e contexto tectônico das rochas da área de Tucumã.
(Universidade Federal do Pará, 2019-09-16) SILVA, Luana Camile Silva; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The Carajás Province (CP) represents the largest preserved Archaean core of the Amazonian Craton with worldwide correspondents. Thus the Tucumã área, located in the northwest portion of the Rio Maria Domain (RMD) near the tectonic border with the Carajás Domain (CD), is marked by the occurrence of mesoarchean age granitoids. This study deals with the discrimination and characterization of this region granitoids which according to the regional studies is dominated by the Rio Maria suíte, by Xingu Complex rocks and metamafics of the greenstone belts sequences. However since data obtained in this work with geological mapping in detailed scale showed that the geological framework of Tucumã is much more diverse and complex. So that contrary to previous studies the most expressive unit in the region are high-K leucomonzogranites rocks that occur as a large plúton. Associated to this pluton small enclaves of granitoids of various compositions are presente in the form of lenses, controlled by NE-SW and E-W anastomosed shear zones. These bodies distinction led to the recognition of five groups: i) high-K Leucomonzogranite; ii) high-HFSE Granites subdivided into medium- and high-Ba; iii) porphyry médium-K Granodiorite; iv) high-Mg Granodiorite; and v) high-Na Tonalite. The granitoids have affinity with the calc-alkaline series, other than high-Na tonalites which follow the trondhjemitic trend with TTG affinities. The latter refers to magnesian granitoids Na2O rich (low K2O/Na2O ratio) which also differ from the others due to the N-S structural pattern often found in greenstone belt sequence, associated with an older tectonic in the region. The moderately fractionated REE patterns (medium La/Yb and Sr/Y ratios) and absence or small negative Eu anomaly typical of TTGs, are features similar to those of médium La/Yb ratio Mogno trondhjemite. With regard to the calc-alkaline units the porphyry médium-K granodiorites differ from the others by the magnesian feature and higher enrichment in Na2O (médium K2O/Na2O ratio) which set forth a resemblance to the TTG suites. However the médium-K granodiorites have higher levels of Ba, K and Th than TTG composition rocks, indicating strong similarities to the so-called transitional or enriched TTG suites. The small differences in the geochemical pattern of these two units are related to changes in the source, where the TTGs (high-Na tonalites) would be the product of the partial melting of a hydrated mafic source (metabasalts), on the other hand the transitional TTGs (porphyry médium-K granodiorite) would originate from melts of a heterogeneous crust with intercalation of enriched basalts and felsic layers. The high-Mg granodiorites occurs in a restricted way in Tucumã identified only in two outcrops. They are distinctly more enriched in Sr and mantle elements (Mg, Cr and Ni) and impoverished in HREE regarding the other granitoids. These features show strong affinities with the sanukitoides suites (Rio Maria Granodiorite) linked to the partial deep melting of the metassomatized mantle. The high-HFSE Granites (medium- and high-Ba) share geochemical characteristics with both the sanukitoide suite and the high-K leucogranites suíte similar to Hybrid granites like the Closepet-type. These suites represent different degrees of interaction processes (mingling or mixing), in the middle crust between crustal melts (tonalites/metassediments) and enriched mantle differentiated melts. Whilst the high-K leucomonzogranites represent the most evolved rocks in the region, where its enrichment in LILEs (Ba, K and Rb) and presence of the negative Eu anomaly indicates crustal reworking processes of an ancient felsic (tonalitic) crust at intermediate crustal levels. This unit has affinities with tha Xinguara and Mata Surrão granites. Regarding the deformation pattern, the rocks with the highest degree of deformation are the high-Na tonalities, in the other units this pattern is only identified in the portions where the shear zones are located. The observed textures (mantle-core and microcracks textures) suggest the operation of deformation processes during the magma crystallization typical of sintectonic granitoids under high temperature conditions (>500ºC). Less deformed granitoids present evidence of dynamic recrystallization at temperatures below 400°C. Thus, in RMD two phases of magmatism are identified, being the first one (2,98-2,92 Ga) related to a subduction setting under an oceanic plateau or a thickened mafic crust with melting at different crustal levels (crust root and slab), and mantle metassomatization by TTG melts and fluids. The second phase (~2.87 Ga) starts from thermal events (slab breakoff, delamination or mantle plumes) that results in partial meltilng of the metassomatized mantle with production of sanukitoide magmas and hybrid granites. This results in changes of the crustal root thickness that lead to substancial temperature variations sufficient to generate partial melting in and beneath the crust associated to generation of high-K granites.
Acesso aberto (Open Access)
Geologia e petrologia do extremo norte da Serra do Estrondo (GO)
(Universidade Federal do Pará, 1984-05-02) SOUZA, Antonio Celso Costa de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
Acesso aberto (Open Access)
Geologia e petrologia dos enxames de diques máficos da região de Santa Maria das Barreiras-Conceição do Araguaia: evidências de eventos distintos de magmatismo intracontinental no Centro- Norte do Brasil.
(Universidade Federal do Pará, 2019-10-28) CRUZ, Danilo José do Nascimento; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
N-S and NNW-SEE-trending subparallel mafic dike swarms are intruded into metasedimentary rocks of the Tocantins Group, Araguaia Belt, central-north Brazil. They are under-examined and there is little to no information about their origin and mantellic sources and uncertainty about their ages. Representative mafic dikes from the Santa Maria das Barreiras-Conceição do Araguaia region, at the boundary between the states of Pará and Tocantins, were studied in order to address these problems. It was possible to separate the dikes into two groups: one consisting of diabases affected by the Neoproterozoic regional metamorphism of the Araguaia Belt with varied degrees of transformations and mineral deformation; and the other consisting of unmetamorphosed and undeformed diabases and leucodiabases. The studied dikes are compositionally classified as subalkaline basalts with tholeiitic affinity. However, metadiabases present an arc-like geochemical signature characterized by a pronounced Nb-Ta negative anomaly, whereas leucodiabases and diabases lack a negative Nb-Ta anomaly and show a LREE-enriched pattern, which resembles the signatures of plume-generated basaltic rocks. Both group of dikes were interpreted to be originated in an intracontinental setting with the aid of Ti–V, Zr–Zr/Y and Zr–Ti discrimination diagrams. There is evidence of important contribution of enriched (EN) mantle components in the source of metadiabases and significant contribution of primitive mantle (PM) to the source of both leucodiabases and diabases. We suggested that the metadiabases represent the exposed plumbing system of arc-like intracontinental basalts which precede the regional Neoproterozoic metamorphism of the area and the leucodiabases and diabases represent the exposed conduits of intracontinental basalts whose magmatism succeed the metamorphic event. The rocks from the older event share several similarities with Neoproterozoic mafic rocks from the eastern domain of the Araguaia Belt and nearby Tonian rocks of the 1100 Ma Rincón del Tigre-Huanchaca LIP event, while the rocks from the newer event are remarkably similar to nearby CAMP basalts and diabase dikes.

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