Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604

O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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Estudo da geometria e cinemática das rochas sedimentares arqueanas da mina do Igarapé do Azul – Carajás-PA
(Universidade Federal do Pará, 2006-09-18) SILVA, Daniela Cristina Costa da; PINHEIRO, Roberto Vizeu Lima; http://lattes.cnpq.br/3251836412904734
The Igarapé Azul Mn Mine is geologically situated along the Carajás Fault trace, in the central portion of the Carajás Strike-slip System. The Mn ore deposit is related to politic sedimentary rocks of the Azul Member on the basal portion of the Águas Claras Formation (Archaean). This unit overlain unconformably the Grão Pará Group (Nogueira et al., 1995). At present day three explotation pits are opened in the mine: (1) Main Mine (Mine 1); (2) Mine 2 and (3) Mine 3. In these locations excellent outcrops of siltstones intercalated with finegrained mudstones, sandstones and Mn-layers are exposed. These rocks are organized in folds and normal/reverse faults sets under heterogeneous deformation, partitioned in different scales. The geologic sections exposed in the mines show the dominance of siltstones intercalated with mudstones in contact with pelitic manganesiferous rocks and ore (Mn bioxide). Primary structures such as hummocky stratification, cross stratification and parallel laminations are common in these rocks. Bedding with thickness of centimeters to a few meters (30-50 cm) represents the main primary structure, used as the main deformation marker observed in rocks. The Igarapé Azul Mn Mine is divided into two blocks separated by normal fault with displacements of tens of meters, where the north block is up in relation to the south one. The south block is poorly deformed, with irregularities in bedding which dips at shallow angles towards south, subsequently positioning the ore layer in deeper levels at S direction. In the north block bedding shows heterogeneous behavior. Deformation is more expressive in this region, with the ore deformed by folds and reverse faults. Faults show vertical along-dipping kinematics with dextral conjugated displacements of oblique character. This region can be defined as a major strain corridor. The kilometer-scale corridor observed at the north block follows the NW-SE trend, in concordance with the main domains separated by the faults described above, characterized as curvilinear asymmetric folds with NW and SE shallow plunge axes (10º-25º). These folds are sectioned by sinuous NW-SE and/or E-W normal faults with shallow dips (10º-30º) associated with dextral strike-slip faults, which generate drag folds. Straight or sinuous NW-SE reverse faults and sub-vertical fault zones are observed. The individual folds in this area are flexural reverse structures with en echelon geometry and similar orientation to the curvilinear folds: shallow SE plunging axes. The features described above drawn a gentle kilometer-scale antiform, which results from bedding accommodation in response to the faulting deformation. The parallelism of the features observed in the Igarapé Azul Mn Mine and the main lineaments which drawn the Carajás Fault suggest a close relation between important deformational episodes occurred during the tectonic history of the Carajás Fault. Faults with normal kinematics associated to directional dextral component of displacement are the major exposures in the area and are related to the dextral transtensional episode responsible for installation of the Carajás Fault prior to 2.6 Ga (Pinheiro, 1997). Folds, thrust faults and subvertical fault zones would be related to deformation under sinistral transpressional regime; a second event responsible for the reactivation and tectonic inversion of most of the primary structures near the Carajás Fault zone (Pinheiro, 1997; Pinheiro e Holdsworth, 2000; Lima, 2002).
Acesso aberto (Open Access)
Geologia e geocronologia Pb-Pb em zircão e Sm-Nd em rocha total de granitóides da região de Santana do Araguaia-PA
(Universidade Federal do Pará, 2012-06-04) CORRÊA, Lívio Wagner Chaves; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
Previous studies consider the region of Santana do Araguaia (PA) is a continuation of the Granite-Greenstone Terrain of Rio Maria (TGGRM) age mesoarqueana (3.0 to 2.86 Ga) is therefore interpreted as belonging to the Carajas Province Central Province or Amazon, Amazon Craton. However, recent studies have provided valuable insights, based on new geochronological data by evaporation Pb zircon, a geological context different from those presented in previous studies, suggesting a reworking of Archean rocks during Transamazonic Event. In this context, the new proposal lithostratigraphic, structural data and geochronological data allowed individualize Domain Santana do Araguaia (DSA), independent of the Carajas Province, in the case of another segment of the Amazonian Craton consists of deformed granitoids, gneisses, migmatites and sequences supracrustal with strong structuring seconds NW-SE direction, this area was included in the province or the province Transamazonas Maroni-Itacaiúnas. The area faces east and north with TGGRM in the west to the Domain Iriri Xingu basin and south with the Araguaia Belt and Parecis. Despite the more recent work performed, Domain Santana do Araguaia is still a little known sector of Pará territory, the existing geochronological data are restricted and were obtained through systematic Rb-Sr and K-Ar in the northeastern state of Mato Grosso and correlated with rocks of the DSA. But at the Para's DSA, only two units (orthogneiss Rio Campo Alegre and Rio Eighteen Tonalite) were preliminarily dated by Pb-Pb method on zircon, lacking thus confirming and expanding to other units in the region, such as Complex Santana do Araguaia greater expressiveness in the area. Also noteworthy was the lack of Sm-Nd isotopic data in this area. In this sense, the real meaning of DSA was not yet understood, because, among other facts, the information gap geochronological, to clarify the relationship between units of DSA with those of TTGRM. Considering these issues, the main objectives of the study are aimed to: a) determine the age of the protoliths of the rocks in the area, to identify lands that are Archean and Paleoproterozoic, using the Pb-Pb method (evaporation) in single crystal of zircon; b ) determine the age of the events of continental crust formation method using the Sm-Nd (whole rock); c) discuss the stratigraphic and chronological rocks to establish the evolution of the southeastern sector of the Amazonian Craton. In field studies were studied nineteen outcrops, whereas petrography and modal analyzes were performed on fourteen samples of rocks (2000 dots / thin section) that were plotted in diagrams QAP and Q-(P + A)- M 'focussed fields of monzogranites, granodiorite and tonalite and individualized in five lithotypes: Biotite monzogranite; Biotite Metagranodiorito; Hornblende-Biotite Granodiorite; Hornblende-Biotite Tonalite Metatonalito and Orthopyroxene. The last two lithotypes were first identified in the region. From a structural standpoint, the foliated biotite Metagranodiorito presents with EW direction, coincident with the regional trend of TGGRM, while the hornblende-biotite foliation have metatonalites following the NW-SE direction, with subvertical dips usually not matching the regional behavior. Microstructural analyzes identify deformation features in minerals such as wavy extinction, kink band, formation of subgrains and dynamic recrystallization. The lithotype Biotite monzogranite is isotropic and hornblende-biotite granodiorite and tonalite Orthopyroxene have only an incipient orientation of its plagioclase crystals, visible only under microscopic observation. Geochronological studies Pb-Pb zircon form performed in six samples and analyzes were made only five Sm-Nd (whole rock) using the spectrometer Finnigan Mat 262 and MC-ICP-MS Neptune, respectively, at the Laboratory of Isotope Geology (Para- iso) of the Federal University of Pará estuos The results of the different rock types are: Biotite Metagranodiorito 3066 ± 3 Ma (ML-04) and 2829 ± 13 Ma (ML-20), hornblende-biotite Metatonalito 2852 ± 2 Ma (ML- 17): Biotite monzogranite from 2678 to 2342 Ma (ML-08): Hornblende-Biotite Granodiorite 1990 ± 7 Ma (ML-16): Orthopyroxene Tonalite and 1988 ± 4 Ma (ML-13). Although Biotite monzogranite has not indicated precise age, the field data indicate a relationship in Biotite Metagranodiorito intrusive. In the case of Sm-Nd analyzes (whole rock) was selected the following samples that follow with their respective age-TDM Model: ML-04 = 3.14 Ga, ML20 = 2.91 Ga, ML-17 = 3 07 Ga; ML-16 2.68 ML-13 and Ga = Ga 2.35. The Sm-Nd isotopic data suggest that if they represent mixtures of magmas, possibly around 3.14, 3.07, 2.91, 2.68 and 2.35 Ga was extraction of magma from the mantle to the crust. Structural studies on macro and microscale feature the installation of a ductile shear zone, transcurrent character, with NW-SE direction, possibly sinistral, located in the eastern portion of the area, which mainly affected the lithotype Hornblende-Biotite Metatonalito. However, this deformation pattern is not observed in the central-southern area nor in the northern portion), where are located the areas of older rocks, which have approximately EW direction of foliation. Analyzing the ages of crystallization of the samples ML-04, ML-17 and ML-20 (3066 ± 3 Ma to 2829 ± 13 Ma) and model ages (3.14 to 2.91 Ga), the values are similar to those reported TTGRM the rocks, leading to the interpretation that the DSA is possibly a continuation of TTGRM southwest. Moreover, the results geochronological sample ML-16 and ML-13 (1990 ± 1988 ± 7 Ma and Ma 4) indicate a newest magmatism of paleoproterozoic.
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Geologia, controle estrutural e geocronologia das rochas hospedeiras e do minério: implicações para o modelo genético do depósito aurífero do Palito, Província Tapajós, Itaituba-PA
(Universidade Federal do Pará, 2016-09-24) SERRA, Vitor Felipe Hage; TORO, Marco Antonio Galarza; http://lattes.cnpq.br/8979250766799749
The Palito gold deposit, located at east portion of the Tapajós Gold Province, southwestern Pará State, comprises a nearly vertical mineralized quartz vein system, hosted by the Palito and Rio Novo Paleoprooterozoic granites and controlled by a sinistral strike-slip brittle-ductile shear zone, trending to NW-SE direction, which belongs to the regional Tocantinzinho lineament. The host granites are two oxidized calc-alkaline monzogranite stocks of Orosirian age and magmatic arc affiliation, correlated to the Parauari Intrisive Suite. The thicker lodes of the veining system are hosted by the major shear, along the N40-50W direction, whereas the thinner veins are housed by faults and fractures of second order and oblique to the main shear direction, both at low angle (around 20), moderate angle (nearby 50) and high angle (around 80). Such a structural situation is compatible with the Riedel system, with the major lodes parallel to the main shear direction (D), associated with low-angle veins (in R and P faults), moderate-angle gash veins (in extension T fractures) and high-angle veins (in R’ an X faults). Stockwork veinlets also occur as a minor ore type. The veins are always involved by a well-developed, normally brecciated, hydrothermal alteration halo. Phyllic alteration (quartz + phengite + pyrite) and chloritization are the two main hydrothermal alteration types, associated to minor potassic alteration (K- feldspar), carbonatization (calcite + sericite + quartz) and sufidation (pyrite + chalcopyrite + sphalerite). Three generations of hydrothermal veining quartz are well characterized in the Palito gold deposit. The youngest low-angle veins (R and P) are made up by quartz1, whereas the later thicker lodes (D) are composed by quartz1 and 2. Tension gash quartz veins may occur at any time of the hydrothermal system evolution and are made up by both quartz1 (youngest gash veins) and quartz2 and 3 (later gash veins). Gash veinlets of quartz3 correspond to final stages of the Palito hydrothermal process. The gold ore, hosted chiefly by quartz1 and 2 veins, is always associated to iron and copper sulfides (pyrite and chalcopyrite), besides sphalerite. Pyrrhotite, bismuthinite, galena, native bismuth and gold are minor metallic phases. Three generations of pyrite and chalcopyrite and one generation of sphalerite were recognized. Chalcopyrite1 replaces pyrite1 and it is replaced by sphalerite, which, in turn, is replaced by chalcopyrite2. Pirite2, coeval to sphalerite, occurs in mineralized veins as anhedral masses replacing tiny remnant grains (islands) of chalcopyrite1, showing concave or corroded edges. Gold is always associated or included in chalcopyrite1 and 2 and pyrite2, bismuthinite and native bismuth crystals. Veinlets of pyrite3 and chalcopyrite3, crosscutting sulfide masses in transtension zones of tiny sinistral faults, are the latest sulfide generations. Two generations of phengite and chlorite were identified in the gangue minerals, being veinlets of phengite2, chlorite2 and carbonate the last one. Fluorite, rutile, zircon and ilmenite still occur as minor gangue phases. The Pb-Pb age of 179417 Ma, obtained for the Palito ore, was interpreted as rejuvenation of the Pb-Pb system caused by Sthaterian alkaline granitic magmatism (Porquinho Intrusive Suite) related to the third extensional deformation phase. The geological features of the Palito gold deposit, as structural controlled veining style of ore bodies and hydrothermal alteration halos, predominating sericitization and cloritization and metallic association (Au-Cu-Bi-Zn) of the ore, all favor classification of the Palito deposit as intrusion-related vein gold deposits. It is a non-porphyritic intrusion-related deposit type, possible related to alkaline granites of the Maloquinha Intrusive Suite, which occur around the Palito deposit. The granitic magma should has provided the ore fluids and metals and the shearing should has controlled the fluid circulation and ore deposition of the Palito deposit.
Acesso aberto (Open Access)
Geoquímica e geocronologia U-Pb em zircão e Sm-Nd em rocha total do magmatismo tardi-transamazônico da região de Calçoene, norte do Amapá, sudeste do Escudo das Guianas
(Universidade Federal do Pará, 2018-05-03) SILVA, Lilian Paula Almeida da; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
The region of Calçoene (Paleoproterozoic Lourenço Domain), northern part of Amapá, Brazil, belongs to the Maroni-Itacaiunas Province, southeast of the Guiana Shield, which represents an extensive Paleoproterozoic orogenic belt developed during the Transamazonian orogeny (2,26-1,95 Ga). The Lourenço domain consists mainly of metavulcanosedimentary sequences, gneissic complexes, several calc-alkaline granitoid suites related to magmatic arc context (2,26 to 2,09 Ga) and granitic plutons, including charnockites that represent syncollisional to late-orogenic stages (2.1 to 1.99 Ga). The present study is focused on the Cunani Granite (~2.10 Ga), the main unit of the Calçoene area. Subordinately, the Cricou Suite (2.11-2.09 Ga), adjacent to the Cunani Granite, was studied at the comparison level. In spite of the recent progress in the regional geological knowledge conducted by the CPRM, geochemical and geochronological data are still scarce and make it difficult to establish a reliable chronology and geodynamic context of this magmatism, as well as to the evaluate the processes of juvenile accretion and crustal reworking during the Transamazonian orogeny. In order to better characterize the late-Transamazonian magmatism and to evaluate the influence of Archaean crustal material on the Rhyacian magmatism in the Lourenço Domain, petrographic study, geochemistry, LA-ICP-MS U-Pb zircon geochronology and Nd-Sr isotopic study were performed and provided important contributions about the geological evolution of this portion of the Guiana Shield. The petrographic study allowed to characterize the Cunani Granite as an unit constituted by dominant biotite monzogranites and biotite sienogranites, subordinate hornblende-biotite tonalites and biotite granodiorites, which contains enclaves of granulites (quartz-diorites with orthopyroxene), and hornblende metatonalites. Rocks of enderbitic composition were also found in this unit. The Cricou Suite in the study area is constituted by biotite monzogranites, and subordinate enderbite was also identified. The geochemical characteristics of these rocks are consistent with both a magmatic arc and syn- to post-collisional context. Most samples displayed enrichment in incompatible elements with high contents of Large Ion Lithophile elements (LILE) like Ba and K, while some High Field Strengh elements (HFSE) such as Th, La, Ce and Nd also show relatively high values. Significant negative anomaly of Nb and P are observed in the rocks of the Cunani Granite and its enclaves. The two samples of the Cricou Suite present Nb positive and negative anomaly, respectively. The Rare Earth Elements diagram showed enrichment of the light elements in relation to the heavy elements in the two units. Only the Cricou Suite shows accentuated positive anomaly of Eu. Overall, the geochemical features are interpreted as of post-collisional magmatism related to tectonic accretion of magmatic arc to the continent. The LA-ICP-MS U-Pb dating of zircon from lithotypes of the Cunani Granite furnished ages of 2097±17 Ma (upper intercept) for a biotite sienogranite (DAC-08-06), 2017±73 Ma (upper intercept) and 1990±16 Ma (concordant age) for another biotite sienogranite (LKV-06-03) and 2019±53 Ma (upper intercept) and 1995±37 Ma (concordant age) for a sample of biotite monzogranite (DAC-08-09a). These ages confirm a late-Transamazonian age (Neorhyacian) for this unit and suggest that the Cunani Granite may encompass different magmatic pulses. The granulitic enclaves of the Cunani Granite (DAC-08-07b) furnished an LA-ICP-MS U-Pb zircon age of 2112 ± 10 Ma and may represent deeper crustal-level rocks that correspond in depth to the migmatization event that affected the rocks of arcs around 2.11-2.10 Ga during the collisional stage. The age around 2.0 Ga obtained for the biotite monzogranite (DAC-08-09a) at the same outcrop than the hornblende metatonalite (DAC-08-09b) previously dated at 2151 ± 2 Ma (TIMS Pb evaporation in zircon) allows to reinforce that the latter corresponds to enclaves of rocks from the Mesorhyacian magmatic Arcs within the Cunani Granite. U-Pb dating by LA-ICP-MS of zircons from a biotite monzogranite (DAC-08-11) of the Cricou Suite provided an age of 1839 ± 62 Ma considered as statistically unreliable. However a resetting of the U-Pb zircon system by younger events cannot be ruled out. The Paleoproterozoic crystallization ages obtained in the analyzed samples and the Archean NdTDM model ages between 3.17 and 2.51 Ga, together with negative values of εNd[2.08 Ga] between -8.67 and -0.72, besides inherited zircons with ages of 3056±63 Ma and 2654±43 Ma identified in a biotite sienogranite, indicate the contribution of Meso-Neoarchean crustal sources during the formation of the Cunani Granite. The Sr-TUR model ages ranged from 2.52 to 2.29 Ga, also indicating Siderian-Neoarchean signature for the source of these granitoids, compatible with tectonic accretion of the magmatic arc with continental landmass.
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Petrologia e geocronologia do magmatismo granítico do Cinturão Araguaia
(Universidade Federal do Pará, 2017-11-28) SILVA NETO, Juvenal Juarez Andrade da; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
In the eastern region of the Araguaia Belt (AB), in Tocantins State, four relatively small granitic bodies are identified: Ramal do Lontra (GRL), Presidente Kennedy (GPK), Barrolândia (GBR) e Santa Luzia (GSL). These rocks represent the record of an important granitogenesis event that is related to the evolution of the AB at the later Neoproterozoic. The few geological data on these bodies were poorly organized which precluded an integrated understanding and the correlation with other outcropping areas. This magmatism is not spatially very representative, but it is important due to the relationship of the granitic emplacement with the main phase of the regional metamorphism. This work is focused on the petrological and geochronological interpretation of granitic magmatism of the AB, especially on the petrographic and geochemical characterization of the main bodies, definition of ages of the magmatic episodes by zircon U-Pb dating and investigation of sources and time of crustal residence by TDM model ages (Sm-Nd) and Nd values. The studied bodies comprise stocks with slightly oval shapes and size that varies from 3 to 6 km on the major axis and 2-8 km on the smaller one, which are emplaced on micaxistes and quartzites of the Estrondo Group. In field stage, some important features were noted, such as the lack of the contact metamorphism and xenoliths on the country rocks, as well as the lack of the cooling borders, presence of granitic portions on the country rocks and the structural concordance between the foliations of the country rocks and the granitic body. The rocks were classified as two-mica meta-granites with low mineralogical variation, low mafic mineral content (<6%), hololeucocratic, medium grained and equigranular features, and granoblastic and relic granular hypidiomorphic textures. On the QAP diagram, the GRL, GBR and GSL plotted on the monogranite field or on the limits between the monzogranite and granodiorite fields, whereas, the GPK felt on the granodiorite field. The essential mineralogical content is formed by oligoclase, quartz and microcline, followed by biotite and muscovite. The accessory minerals are represented by apatite, zircon, allanite, garnet, monazite and opaque minerals. The granitic rocks are geochemically similar with SiO2 content from 71% to 74%, and Al2O3 between 13% and 15%. The Na2O and K2O contents are slightly higher in the GRL and GPK, which reflect on the A/CNK ratio, plotting on the peraluminous field. The low content of MgO, Fe2O3Total and CaO indicate these rocks are low fractionated. The trace elements also pointed out small compositional variations on the rocks of the different bodies. The REE patters demonstrated a medium to strong fractionation of the light REE in relation to the heavy REE, showing (La/Yb)N values between 11.8 and 72.8 and week Eu anomalies (Eu/Eu* = 0.5-1.3). The zircon U-Pb dating by SHRIMP reveled ages of 542.7 ± 1.9 Ma (GPK), 541.5 ± 1.8 Ma (GBR) and 546.4 ± 2.3 Ma (GSL). These ages were interpreted as zircon crystallization at the later Neoproterozoic. The age obtained for the GRL was slightly older (615,7 ± 26 Ma) with a higher MSWD errors. The Sm-Nd isotopic results for the four bodies reveled TDM model ages between 1.69 and 1.84 Ga and Nd values from -12.18 to -6.21. On the Nd versus time diagram, the plots indicate a dominantly Statherian crustal sources for the parental magmas. The integrated data analysis allows us to suggest that the granitic bodies are correlated, which their origin is associated to a same granitogenesis event. The U-Pb ages between 541 and 546 Ma, interpreted as crystallization of the GPK, GBR and GSL, are related to the main metamorphic phase of the AB. The emplacement of this bodies is associated to the orogenic collisional phase of the AB at the later Neoproterozoic. The Sm-Nd data suggest that the studied rocks were generated by anatexia of at least two different sources, which favored the aggregation of granitic melts, rising and late emplacement of these magma at the main phase of the Araguaia Belt.

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