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) Petrogênese da Suíte Igarapé Gelado: implicações para o magmatismo neoarqueano da Província Carajás, Cráton Amazônico(Universidade Federal do Pará, 2025-04-30) MESQUITA, Caio José Soares; DALL’ AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675The Igarapé Gelado suite (IGS) is located near the northern border of the Carajás Province, almost at its boundary with the Bacajá Domain, along the Cinzento lineament, and is intrusive in metavolcanic mafic rocks and banded iron formations. The central-eastern portion of the IGS comprises four rock varieties: tonalite to granodiorite with varying contents of biotite and amphibole, (1) with associated clinopyroxene and/or orthopyroxene (PBHTnGd) or (2) devoid of pyroxenes (BHTnGd); and monzogranites that exhibit variable biotite and amphibole content and can be (3) moderately (BHMzG) or (4) strongly (RBHMzG) reduced. The PBHTnGd shows ferrosilite and/or augite with subordinate hedenbergite. The amphiboles are K-hastingsite and, subordinately, Fe-Tschermakite in monzogranites. Biotites are ferroan, and in reduced granites show #Fe > 0.90. These micas are similar to those of alkaline to subalkaline rocks and compositionally akin of primary magmatic biotites. Plagioclase is oligoclase. The integration of thermineral chemistry;mobarometry results and thermodynamic modeling and their comparison with the paragenesis present in natural rocks improved the estimation of crystallization parameters (T, P, ƒO2, H2O), and allowed a better interpretation of magmatic evolution. The IGS granites crystallized at pressures of 550 ± 100 MPa, higher than those attributed to other Neoarchean granites in Carajás provinve. The estimated liquidus temperature for the IGS pyroxene variety is ~1000±50°C. BHTnGd and BHMzG formed within a similar temperature range to PBHTnGd, while RBHMzG had lower liquidus temperatures (≤900°C). Solidus temperatures of around ~660 °C were estimated for the four IGS varieties. The BHMzG magma evolved under conditions of low ƒO2, slightly above or below the FMQ buffer (FMQ±0.5), like those of the Planalto suite and the reduced granites of the Vila Jussara and Vila União suites of Carajás province. In the magmas of the PBHTnGd and BHTnGd varieties the oxygen fugacity attained FMQ+0.5. The RBHMzG crystallized under strongly reduced conditions equivalent to FMQ-0.5 to FMQ-1. The magmas of the monzogranitic varieties evolved with a H2O content of ≥4 wt%, attaining 7 wt% in the case of the reduced monzogranites. This is comparable to, or slightly exceeding, the levels typically attributed to the Neoarchean granites of Carajás province (≥ 4% wt%). In contrast, the variety with pyroxene has a water content (~4 wt%) like that of Café enderbite and Rio Seco charnockite from Carajás province, and Matok Pluton from Limpopo belt. Based on the chemical composition, the rocks from IGS are ferroan, reduced to oxidized A-type-like granites, akin to other Neoarchean granite suites from the Carajás province. The IGS are younger than the 2.76-2.73 Ga Neoarchean granites from the Carajás province. A crystallization concordia age of ~2.68 Ga was obtained by U-Pb SHRIMP in zircon for the RBHMzG variety, and similar upper intercept ages were furnished by the other IGS varieties, except for ages of ~2.5 Ga that resemble the ages of the IOCG Salobo deposits associated with reactivation of the Cinzento Lineament. Tmineral chemistry;he deformation of the IGS rocks was influenced by shear zones linked to that lineament, forming elongated bodies with varied foliation. These zones facilitated the migration and deformation of magmas from the final crystallization stages until their complete cooling, characterizing a syntectonic process. This syntectonicity is associated with the inversion of the Carajás Basin, and the younger crystallization age of these rocks indicates that the inversion occurred up to 2.68 Ga, extending the previously estimated interval (2.76– 2.73 Ga). The IGS displays negative to slightly positive values of εNd(t)(-2.86 to 0.18) and εHf(t)(-3.3 to 0.1), and Paleoarchean to Mesoarchean TDM ages [Nd-TDM(2.98-2.84) and Hf-TDM C (3.27-3.12)]. The positive values of εNd(t) and εHf(t) for the RBHMzG variety, suggest possible juvenile contribution or contamination in the source of its magma. The IGS rocks come from the melting of 19% (PBHTnGd) or 14% (BHTnGd) of contaminated mafic granulite, - and from melting of 9% (BHMzG) and 7% (RBHMzG) of a tholeiitic mafic granulite. The area of occurrence of the IGS is marked by hydrothermalism and mineralizations that locally modified the composition of rocks and minerals, allowing the leaching of REE and Y that changed the composition of some samples of BHMzG approaching them of (false) A1- subtype granites. In addition, these processes were responsible for zircon alteration, which resulted in grains showing enrichment of U, Th, and LREE, and massive textures, that furnished upper intercept U-Pb ages, contrarily to the zircon crystals of the RBHMzG variety that preserved primary characteristics and presented Concordia ages.Item Acesso aberto (Open Access) Petrografia e evolução crustal da porção sul do Domínio Pacajá, Cráton Amazônico: evolução policíclica do Mesoarqueano ao Riaciano(Universidade Federal do Pará, 2025-08-13) NERI, Arthur Santos da Silva; DALL’ AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675The integration of field, petrographic, mineralogical, geochemical, geochronological (U-Pb in zircon, monazite, and titanite), and isotopic data (Sm-Nd in whole rock and Lu-Hf in zircon) undertaken in the southern portion of the Bacajá Domain enabled the identification and characterization of new granitoid and charnockitic units previously encompassed within the Cajazeiras Complex. These discoveries allowed a redefinition of the regional stratigraphy and advancing the understanding of the crystallization conditions, origin, and evolution of magmatic and metamorphic orthoderived rocks. A long-lived Rhyacian magmatic event (~70 Ma) was recognized, beginning around 2.12 Ga and lasting until 2.05 Ga. During this interval, the following units were identified: Bandeirante (2.12 Ga, εHf(t) = -6.5 to -4.6, εNd(t) = -3.40); and Alto Rio Preto (2.10-2.06 Ga, εHf(t) = -10.2 to -6.3, εNd(t) = -8.96 -2.80) granites; Maravilha (2.09 Ga, εHf(t) = - 9.2 to -8.2, εNd(t) = -3.01 to -1.91) and Serra Azul (2.07 Ga, εHf(t) = -8.8 to -5.8, εNd(t) = -6.44 to -4.71) charnockites; Bernardino granite (2.05 Ga, εNd(t) = -6.71). Geochemically, the units are mostly high-K calc-alkaline and magnesian (Alto Rio Preto and Bernardino granites, Serra Azul charnockite), transitioning to calcic or alkali-calcic and ferroan (Bandeirante granite and Maravilha charnockite, respectively). They range from metaluminous to weakly peraluminous, except the Bernardino granite, which is strongly peraluminous. The Nd-Hf isotopic integration indicates a crustal source with strongly negative epsilon values and Archean model ages, with a marked contrast to crystallization ages, pointing to long crustal residence times. These granitoids were generated by the collision between the Bacajá and Carajás domains in a late- to post-collisional setting during the Transamazonian Orogeny. Crustal thickening and subsequent delamination are interpreted as the main mechanisms responsible for partial melting and generation of these magmas. The Nd-Hf isotopic signatures reveal a coherent crustal compartmentalization between the Bacajá, Carecuru and Lourenço (Amazonian Craton) and Bauolé-Mossi domains (West Africa Craton), suggesting that these segments were juxtaposed during the amalgamation of the Columbia supercontinent. The Alto Rio Preto granite is composed of epidote-bearing granites and granodiorites-tonalites. This granite was emplaced at pressures of 0.4-0.7 GPa and temperatures between 949 and ~640 ºC, evolved under oxidizing conditions (NNO±0.5 to ±1), with initial water contents of ~2-6 wt%. The preservation of magmatic epidote results of a complex interaction between generation and emplacement pressures, oxidizing conditions and water content in the magma, combined with low density and viscosity that facilitated rapid magma ascent (4-5 km/year) through the crust, preventing complete epidote dissolution. Field and petrographic data suggest that this granite represents a syntectonic intrusion, with geochemical affinities with high-K calc-alkaline series. The parental magma of the monzogranitic facies was derived from dehydration melting of a basaltic source at 0.99 GPa and 865 °C leaving an amphibolite residuum. These granitoids represent an example of crustal reworking of lower mafic crust and do not contribute to net crustal growth in the collisional zone between the Bacajá and Carajás domains. The Maravilha charnockite comprises two petrographic associations: (i) monzonite-granite-charnockite and (ii) granodiorite-monzogranite, with or without igneous orthopyroxene and fayalite + quartz. The (i) association crystallized at temperatures between 1052 and ~680 °C, and evolved under reducing (FMQ±0.5), with ≤3 wt% initial water contents. The (ii) crystallized at temperatures between 918 and ~680 °C and evolved under oxidizing conditions (NNO±0.5), with ~4 wt% initial water contents. Both associations were emplaced at pressures between 0.3 and 0.6 GPa The Serra Azul charnockite consists of tonalites, granodiorites, and rare granites, with or without igneous orthopyroxene. These rocks were emplaced at pressures 0.3-0.6 GPa, temperatures between 1078 and ~700 ºC, and evolved under oxidizing conditions (NNO±0.7 to ±2), with initial water contents ~ 2-3 wt%. Thermodynamic data indicate that fayalite is restricted to low pressures (≤0.3 GPa) and reduced conditions (FMQ -2 to -0.6), but it can crystallize under water-rich conditions (2.3 to 6.2 wt%, possibly up to 9 wt%). In contrast, orthopyroxene can crystallize over a wide pressures range (0.1-1 GPa), from reduced to oxidizing conditions (FMQ-2 to NNO+2.5), and under moderate water contents (~5.2 to 6.5 wt%). The Cajazeiras Complex comprises tonalitic to monzogranitic orthogneisses crystallized at 2.97-2.94 Ga, followed by Pb-loss/metamorphism at 2.80–2.81 Ga and Paleoproterozoic metamorphism 2.21-2.01 Ga. These rocks show geochemical affinities with sanukitoid s.l., representing the oldest sanukitoid magmatism in the Amazonian Craton and the second oldest worldwide. The Nd-Hf data (εNd(t) +0.65; εHf(t) +0.5 to +2.5) suggest a juvenile contribution and short crustal residence time, with model ages close to the crystallization age. The discovery of these rocks implies that the mantle was already metasomatized in the Mesoarchean and opens possibilities for the presence of other typical Archean rocks in the basement of the domain. These orthogneisses were metamorphosed under upper amphibolite to granulite facies. The metamorphic peak was marked by the assemblage clinopyroxene-amphibole-biotite-quartzmagnetite- ilmenite-melt, under conditions of ~0.52–0.55 GPa/760–790 °C at ~2.21 Ga. Cooling toward the solidus occurred at ~ 2.10-2.08 Ga, and retrograde metamorphism is represented by the amphibole-biotite-quartz-magnetite-ilmenite-H₂O assemblage, developed under ~0.40–0.48 GPa/600–650 °C at ~2.01 Ga.