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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Item Acesso aberto (Open Access) Estudo de Proveniência das rochas metassedimentares do Complexo Ceará, na região de Sobral e adjacências, com base em datação U-Pb de zircão e idades-modelo Sm-Nd(Universidade Federal do Pará, 2015-06-05) FEITOSA, Jeremias Vitório Pinto; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979The Borborema Province is an important tectonic province, with approximately 450,000 square kilometers in the northeastern Brazil, which registered numerous and remarkable geological processes that occurred on Earth over time. This province has great similarities with existing provinces in Africa, as the Benin/Nigeria. Successive geological cycles are recorded in rock types of the Borborema Province, dating back to a very complex geologic evolution started in the Archean, culminating at the end of the Neoproterozoic, with the occurrence of tectonic-thermal events and magmatism called the Brazilian Cycle, which resulted in the closure of an oceanic domain in this region. The Tamboril-Santa Quitéria Complex (TSQC) is the most significant unit of this final process of continental collision observed in Ceará Central Domain of the Borborema Province. The existent geochronological and isotopic data allow to understand the context and the geological evolution of the unit. However, for the metasedimentary rocks that flank the TSQC, assembled in the Ceará Complex, are lacking studies and information that permits to propose more refined geological models to better understand the evolutionary framework of this region. The suggested Paleoproterozoic age initially suggested for the metasedimentary rocks of Ceará Complex can questioned due to the presently known geological context. Thus, the sedimentary provenance study proposed here using U-Pb detrital zircon dating and Sm-Nd model-age (TDM), aims to investigate the maximum age of deposition of this metasedimentary unit, and the probable the crustal source of these rocks, to contribute to the understanding of the evolution and stratigraphic framework of Ceará Central Domain. This work included the sampling of 20 outcrops of these metasedimentary rocks that occur in the western and in the eastern flanks of the TSQC. Six samples of quartzite were collected for U-Pb zircon analysis using a laser ablation system attached to a multicollector mass spectrometer with inductively coupled plasma (LA-MC-ICPMS). Sm-Nd model-age determination was carried out in 14 samples. Petrographic study of the non-friable samples preceded the isotope analyses. The rocks of the western flanks of the TSQC were garnet gneiss and kyanite gneiss, with dominantly lepidoblastic and even granoblastic textures. Besides, sillimanite quartzite and muscovite quartzite occurs presenting polygonal granoblastic textures. In the eastern portion, the rocks were observed garnet gneiss with lepidoblastic and granoblastics textures in addition to garnet amphibolite with mainly nematoblastic and minor porphyroblastic textures. The Sm-Nd model-ages between 2.12 and 2.7 Ga., and positive values of Nd (2,1Ga) (+3.30 to + 2.60 ) suggests a strong contribution to Paleoproterozoic crust for the sediments located east of TSQC. This contribution is also recorded in the rocks sampled in the west of TSQC. However, TDM model-age of 1.66 Ga found in a rock also suggests contribution of younger crustal source for these metasedimentary rocks. The U-Pb data for quartzites of the Ceará Complex, in general, have prevalence of detrital zircons of Paleoproterozoic ages, more frequently of the Orosirian (1800-2050) and Rhyacian (2050-2300 Ma) periods, suggesting that the main source area of the sediments are Paleoproterozoic age. However the presence of detrital zircon grains of Statherian (1750± 50 , 1777± 58, 1628± 53 Ma) and Stenian age (1154 ± 29 Ma) found in rocks located east of TSQC indicates the input of younger rocks, corroborating the contribution of younger crustal source for the sedimentary succession of Ceará Complex. The age of 1154 Ma, indicates the maximum age of deposition of these sediments suggesting that this depositional event may even have occurred in the Neoproterozoic, as it is suggested by geological and geochronological evidences pointed out by some authors who studied this succession in other regions of Ceará Central Domain.Item Acesso aberto (Open Access) Estudo petrográfico, geoquímico e isotópico de granitos da porção Leste do Domínio Tapajós, nas folhas São Domingos e Jardim do Ouro, Pará(Universidade Federal do Pará, 2015-10-07) SEMBLANO, Flávio Robson Dias; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136The Tapajós Domain, located in Brazil Central shield (southern portion of the Amazonian Craton) makes part of the Tapajós-Parima (or Ventuari-Tapajós), Province corresponding to a Paleoproterozoic orogenic belt of NW-SE direction, extending from southwestern Pará state to southern Venezuela. Some authors describe this province as been formed by development of two distinct orogenies that accreted four magmatic arcs, followed by a post-orogenic alkaline magmatism. This post-orogenic Orosirian magmatism, occurred around 1880 Ma, is represented by the Maloquinha Intrusive Suite (MIS) and Iriri Group that have occured postdating Tropas Orogeny which give rise to Parauari Intrusive Suite (PIS). The MIS comprises alkali granites generated in post-collisional anorogenic environment that is spatially associated with Iriri Group volcanic rocks. This suite consists of alkali feldspar granite, syenogranite and monzogranite leucocratic bodies with predominant pertitic orthoclase and rare microcline. These rocks crop out as elliptical to round stocks and batholiths along NW-SE regional lineaments in the Tapajós Domain. Many bodies belonging to SIM have been dated by both methods, Pb-evaporation and U-Pb on zircon, that yielded ages between 1882±4 and 1864±18 Ma. In the eastern portion of the Tapajós Domain, the Nd isotope signature for these suite granites suggests paleoproterozoic sources (TDM Nd of 2.28 to 2.23 Ga, and εNd(t) of -0.72 to -2.45). Many plutons of SIP were dated by zircon Pb-evaporation method, and the ages found were between 1891±3 e 1879±11 Ma, its isotopic signature of Nd are εNd(t) -5.21 to -1.82 and TDM Nd of 2.43 to 2.32 Ga. This work was carried out in the eastern part of the Tapajós Domain, in the SB.21-Z-A-II (São Domingos) and SB.21-Z-A-III (Jardim do Ouro) 1:100,000 sheets, where five granitic bodies were studied (Igarapé Tabuleiro, Dalpaiz, Mamoal, Serra Alta and Igarapé Salustiano). The Igarapé Salustiano body shows a calc-alkaline affinity, meta to peraluminous and syncolisional I-Type granites nature, showing close relationship with the Parauari Intrusive Suite rocks of this Domain. Other bodies could be related to MIS and they are basically represented by hololeucocratics alkali feldspar granites, syenogranites and monzogranites. These rocks have high SiO2 (>70%), FeOt/(FeOt+MgO) (>0.80) and K2O/Na2O, low CaO, Al2O3, MgO and Sr contents, and post-collisional granites affinity, alkalic-calcic to alkalic character and high REE content with Eu negative anomalies, own from A-type granites. This work, as others made in the Tapajós-Parima and Amazônia Central provinces, identified TDM Nd contradictory ages to the ones assigned these two provinces for geochronological subdivision between them.Item Acesso aberto (Open Access) Paleoambiente e quimioestratigrafia da Formação Itaituba, carbonífero da borda sul da bacia do Amazonas, região de Uruará – Pará(Universidade Federal do Pará, 2014-10-29) CAMPOS, Amélia Carolina Pimenta Parente de; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/886783626882099; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136The Amazon Basin, characterized as an intracratonic basin of about 400,000 km2, has a Phanerozoic sedimentary record of four second- order sequences related to groups Trombetas; Urupadi and Curuá; Tapajós and Javari. The Itaituba Formation, the goal of this work, is part of the Tapajós Group, which represents the last transgressive -regressive cycle of this Paleozoic basin. The Itaituba Formation presents thick packages of subtidal limestones intercalated with thicker evaporite deposits toward the top of the formation, with shales, siltstones and sandstones that represent deposits transgressive – regressive deposits of moderate energy in shallow marine infra-tidal and subtidal environment. The formation is composed of the richest strata of marine fossils in the Amazon Basin, such as the conodonts, foraminifera, corals, bryozoans, crinoids, trilobites, ostracods, gastropods, brachiopods, bivalve, escolecodonts and fish fragments. In this work, it was studied samples from a drill core (FURO 5) obtained in Uruará area, east-central state of Pará. The main objectives of this study are to obtain the depositional age of Itaituba Formation by comparison with the century 87 Sr/86Sr curve and its chemostratigraphic characterization based on major and trace elements contentes, and C and O isotopes, as well as the facies description. The stratigraphic profile of the drill core is characterized by an intercalation between carbonatic facies rich in bioclasts , stylolites and quartz druses and dolomitic facies . At the base of the profile, terrigenous facies characterized by reddish silt with carbonate clasts were recorded. Microfaciologically the following lithotipes were identified: wackstone, packstone, and more rarely dolomudstone, mudstone and grainstone. Seven microfacies were defined: Bioclastic Mudstone (Mcb), Bioclastic Wackstone (Wb), Bioclastic Wackstone with stylolites (Wbe), Bioclastic Packstone (Pb), Bioclastic Packstone with Peloids (Pbp), Bioclastic Grainstone with Peloids (Gbp) and Fine Dolomite (Dl). Among the bioclasts are: brachiopods, echinoderms, foraminifera, pelecipods, bryozoans, gastropods and ostracods. As not skeletal components there are: quartz, clay minerals, feldspars, oóides and intraclasts. The matrix is micritic and there are three types of cement: "fringe", tile and sintaxial overgrowth. Much of the profile was affected by secondary processes such as dolomitization, dissolution and compaction. The results of geochemical analyses were performed on 46 samples collected at each 50 cm, approximately. The data confirm that the profile is predominantly calcitic with small variations in the Mg content, however, dolomitised levels are present. The high values of Si in some samples indicate the presence of terrigenous minerals, in addition to the druses and fractures filled with quartz. The Sr contents of the samples are satisfactory for the isotopic analysis, and varies from 30 to 293 ppm, some of the smaller values being related dolomitic rocks. Stable isotope studies were performed on 76 samples collected at intervals of 30 cm. The values obtained for 13C and 18O range from 1.602 to 5.422 ‰ and - 8.734 to 0.804 ‰, respectively. These values are in accord with those obtained in previous studies for the Itaituba Formation carbonates, pointing a marine environment with the typical isotopic signature of Carboniferous rocks. (13C ranging from 2 to 6 ‰, and 18O ranging from - 3 to 7‰). Therefore, the study carbonates have primary isotopic composition, except for some samples, which have their values affected by diagenetic processes, like the dolomitization. The depositional age was obtained from the leaching of two shells of brachiopods, which positioned the rocks from the Itaituba Formation in the Upper Pennsylvanian with two ages intervals, between 296 and 303 Ma (Virgiliano - Missourian), and between 293 and 307 Ma (Virgiliano - Desmoinesiano), and Lower Pennsylvanian aged between 313 and 318 Ma (Morrowan).