Teses em Geologia e Geoquímica (Doutorado) - PPGG/IG
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O Doutorado 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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Tese Acesso aberto (Open Access) Geocronologia 207Pb/206Pb, Sm-Nd, U-Th-Pb E 40Ar-39Ar do segmento sudeste do Escudo das Guianas: evolução crustal e termocronologia do evento transamazônico(Universidade Federal do Pará, 2006-07-06) ROSA-COSTA, Lúcia Travassos da; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645The southeastern portion of the Guiana Shield is part of a large Paleoproterozoic orogenic belt, with evolution related to the Transamazonian Orogenic Cycle (2.26 – 1.95 Ga). In this area, previous works defined distinct tectonic domains, named Jari, Carecuru and Paru, which present outstanding differences in terms of age, lithological content, structural pattern and geophysical signature. The Jari Domain is constituted of a granulite-gneiss-migmatite basement assemblage derived from Archean protoliths, and the Carecuru Domain is composed mainly of calc-alkaline rocks and metavolcano-sedimentary sequences, developed during the Transamazonian Event. The Paru Domain is an oval-shaped granulitic nucleous, located within the Carecuru Domain, formed by granulitic gneisses with Archean precursors and Paleoproterozoic charnockitic plutons. In this study, distinct geochonological methods were employed in rocks from the distinct domains, in order to define their tectonic meaning and crustal evolution processes during Archean and Paleoproterozoic times. Pb-evaporation on zircon and Sm-Nd on whole rock dating were provided on magmatic and metamorphic units from the Jari Domain, defining its long-lived evolution, marked by several stages of crustal accretion and crustal reworking. Magmatic activity occurred mainly at the Meso-Neoarchean transition (2.80-2.79 Ga) and during the Neoarchean (2.66-2.60 Ga). The main period of crust formation occurred during a protracted episode at the end of Paleoarchean and along the whole Mesoarchean (3.26-2.83 Ga). Conversely, crustal reworking processes have dominated in Neoarchean times. During the Transamazonian Event, the main geodynamic processes were related to reworking of older Archean crust, with minor juvenile accretion at about 2.3 Ga, during an early orogenic phase. Transamazonian magmatism consisted of syn- to late-orogenic granitic pulses, which were dated between 2.22 and 2.03 Ga. Most of the εNd values and TDM model ages (2.52-2.45 Ga) indicate an origin of the Paleoproterozoic granites by mixing of juvenile Paleoproterozoic magmas with Archean components. The new geochronological results, added to data from previous studies, revealed that the Jari Domain represents the southwestern part of the most expressive Archean continental landmass of the Guiana Shield, here defined and named Amapá Block. The recognition of an extended Archean block precludes previous statements that the Archean in the southeast of the Guiana Shield, was restricted to isolated remnants or inliers within Paleoproterozoic terrains. In the Carecuru Domain the widespread calc-alkaline magmatism occurred at 2.19-2.18 Ga and at 2.15-2.14 Ga, and granitic magmatism was dated at 2.10 Ga. Crustal accretion was recognized at about 2.28 Ga, in agreement with the predominantly Rhyacian crust-forming pattern of the Guiana Shield. Nevertheless, TDM model ages (2.50-2.38 Ga), preferentially interpreted as mixed ages, and εNd < 0, point to some participation of Archean components in the source of the Paleoproterozoic rocks. The lithological association and the available isotopic data registered in the Carecuru Domain, suggests a geodynamic evolution model based on the development of a magmatic arc system during the Transamazonian Orogenic Cycle, which was accreted to the southwest border of the Archean Amapá Block. In the Paru Domain, Neoarchean magmatism at about 2.60 Ga was produced by reworking of Mesoarchean crust, as registered in the Amapá Block. Crustal accretion events and calc-alkaline magmatism were recognized at 2.32 Ga and at 2.15 Ga, respectively, as well as charnockitic magmatism at 2.07 Ga. U-Th-Pb chemical ages in monazites from high-grade rocks of the southwestern part of Amapá Block, dated two main tectono-thermal events. The first one was revealed by the monazite ages of about 2.09 Ga and marks the age of the granulite-facies metamorphism. These data, added to petro-structural information, indicate that the granulite-facies metamorphism was contemporaneous to the development of a thrusting system associated to the collisional stage of the Transamazonian Orogeny. The later event was testified by monazite ages at about 2.06 Ga and 2.04 Ga, and is consistent with a late-orogenic stage marked by granitic emplacement and coeval migmatization of the Archean basement along strike-slip zones. Finally, 40Ar/39Ar geochronological study on amphibole and biotite from representative units of the Amapá Block and of the Carecuru Domain delineated contrasting cooling and exhumation stories. In the former amphibole vary from 2.13 to 2.09 Ga, and biotite ages range mainly between 2.10 and 2.05 Ga. In the later, amphibole and biotite ages are between 2.16 and 2.06 Ga, and 1.97 and 1.85 Ga, respectively. In the Amapá Block, fast cooling rates around 67 °C/m.y. and 40 °C/m.y indicate a tectonically controlled exhumation, related to collisional stages of the Transamazonian Event. Conversely, in the Carecuru Domain, regional cooling rates in the order of 3-2.3 °C/m.y. suggest slow cooling and gradual uplift, which is consistent with the magmatic arc model, where continental growth results mainly from lateral magmatic accretion, precluding significant tectonic crustal thickening.Tese 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.Tese Acesso aberto (Open Access) Petrogênese e evolução magmática da Suíte Sanukitóide Rio Maria, Terreno Granito – Greenstone de Rio Maria, Cráton Amazônico(Universidade Federal do Pará, 2009-08-25) OLIVEIRA, Marcelo Augusto de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675; 2158196443144675The Archean sanukitoid Rio Maria suite yielded zircon ages of ~2.87 Ga and is exposed in large domains of the Rio Maria Granite-Greenstone Terrane, southeastern Amazonian craton. It is intrusive in the greenstone belts of the Andorinhas Supergroup, in the Arco Verde, Mariazinha, and Caracol tonalite, and Mogno trondhjemite. Archean potassic leucogranites, Água Fria trondhjemite, and the Paleoproterozoic granites of Jamon Suite are intrusive in the rocks of the Rio Maria suite. The dominant rocks have granodiorite to subordinate monzogranitic compositions, with minor proportions of intermediate quartz-diorites or quartz-monzodiorites rocks, in addition to mafic end members occurring as layered rocks or as enclaves. The Rio Maria suite has clear geochemical characteristics of Sanukitoids rocks (high Mg#, elevated Cr and Ni contents, LREE enrichment, and high Ba and Sr contents relative to typical calc-alkaline series). The significant geochemical contrasts between the occurrences of the granodiorites in different areas suggest that this unit corresponds in fact to a granodioritic suite of rocks derived from similar but distinct magmas. In spite of their broad geochemical similarities, granodiorites, intermediate rocks, and mafic enclaves show some significant differences in their REE patterns and in the behavior of Rb, Ba, Sr, and Y. The granodiorites and intermediate rocks are not related by fractional crystallization and the internal evolution of intermediate rocks were leaded by fractionation of amphibole + biotite ± apatite, whereas granodiorites evolved by fractionation of plagioclase + amphibole ± biotite. The layered rocks should have been derived from the granodiorite magma by accumulation of 50% of amphibole (dark layer) and 30% of amphibole ± plagioclase accumulation (gray layer). Modeling and geochemical data suggest that mafic enclave and granodiorite magmas were originated at different depths and should have mingled during their ascent and final emplacement and a limited interaction would explain the relatively uniform geochemical behavior of each rock variety and the distinct trends displayed by their rocks in different modal and geochemical diagrams. These contrasts between granodiorites and mafic enclaves are reflected in the behavior of the Sr and Y, which are generally seen as good indicators of the pressure of melt formation. The behavior of these elements, observed in different sanukitoid rocks from Archean terranes worldwide, indicates that the geochemical and modal contrasts observed between the granodioritic (granodiorites) and monzonitic (mafic enclaves) sanukitoid series are a general feature of these rocks and their origin is strongly dependent of the pressure of magma generation and, as a consequence, that the nature of the series could indicate the approximate depth of formation of its magma. The petrogenesis of the Rio Maria suite requires melting of a modified mantle extensively metasomatized by addition of about 30% TTG-like melt to generate the granodiorite (21% of melt) and intermediate magmas (24% of melt), and ~20% TTG-like melt in the case of mafic enclave magma (9% of melt). Our modeling results indicate that an active subduction tectonic setting was present in the Rio Maria terrane in between 2.98 to 2.92 Ga to generate the TTG magmas and the proposed metasomatism of the mantle by these magmas, before the melting process responsible for the origin of the sanukitoid magmas. A tectonothermal event at ~2.87 Ga, possibly related to a mantle plume, causing the partial melting of the metasomatized mantle and generating the Rio Maria sanukitoid magmas. In the rocks of the Rio Maria suite, the mineral assemblage is dominated by amphiboleplagioclase-biotite and epidote minerals, all of inferred magmatic origin, pyroxenes being notably absent. Textural and compositional criteria indicate that amphibole is a principal mineral on the liquidus of all the Rio Maria rocks. To derive crystallisation conditions, the phase assemblages, proportions and compositions of the natural rocks were compared with experimental works carried out on similar magma compositions. The comparison shows that the parental magmas were water-rich, with more than 7 wt% dissolved H2O near liquidus, with crystallisation temperature in the range 950-680°C. The Mg/(Mg+Fe) ratios of both amphibole and biotite indicate fO2 conditions in the range NNO + 0.5 up to NNO + 2.5, therefore pointing to both water-rich and oxidizing conditions for sanukitoid magmas. Analyses of amphibole aluminium content in cumulate rocks, indicate in addition a high pressure crystallisation stage, around 700-1000 MPa, prior to emplacement in the upper crust at around 200 MPa. Sanukitoid magmas share therefore two of the principal characteristics of modern arc magmas, elevated redox sate and volatile contents, which suggest that they may have formed in a geodynamic environment broadly similar to present-day subduction zones.Tese Acesso aberto (Open Access) Petrogênese e história tectônica dos granitóides mesoarqueanos de Ourilândia (PA) – Província Carajás(Universidade Federal do Pará, 2022-09-16) SILVA, Luciano Ribeiro da; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506; https://orcid.org/0000-0001-7976-0472Zircon U-Pb-Hf isotopic data from the main Mesoarchean units in the Ourilândia do Norte area (Carajás Province, Amazon Craton) were combined with a review of the main geological-structural, petrographic and geochemical aspects of these rocks, which allowed a redefinition of local stratigraphy, as well as a better understanding of the nature of the sources, based on geochemical modeling. In addition, a modern framework of the tectonostratigraphic correlations and the main events that led to the stabilization of the province was presented, as well as their implications for the origin of the plate tectonics. The Ourilândia granitoids are composed of interdigitated batholiths of sanukitoids and potassic granites, with subordinate TTG. (1) The TTG represent the oldest event in the area (2.92 Ga) and they are composed of tonalitic xenoliths (Mogno suite) and a porphyritic trondhjemite stock (Rio Verde suite), in which biotite is the main mafic mineral. The xenoliths are intensely deformed and the trondhjemite presents small mafic enclaves. The xenolith provided chondritic values of εHf(2.92 Ga) = +2.0 to –0.2 and was formed by partial melting of hydrated metabasalts, while the trondhjemite presented εHf(2.92 Ga) = +2.3 to –3.5 suggesting a more complex origin involving mixing between TTG-type melt and a subchondritic component, reflecting its longer crustal residence time (Hf-TDMC = 3.2–3.5 Ga) in relation to the xenolith (Hf- TDMC = 3.2–3.3 Ga). (2) The sanukitoids were grouped in the Ourilândia sanukitoid suite, which integrates the Arraias granodiorite (2.92 Ga) and the Ourilândia tonalite-granodiorite complex (2.88 Ga), which is composed of tonalites and granodiorites with subordinate quartz monzodiorite, quartz diorite and mafic enclaves. In general, these rocks show hornblende, biotite and epidote as the main mafic phases. The Arraias granodiorite is the oldest sanukitoid unit in the province and one of the oldest in the world. It provided εHf(2.92 Ga) values ranging from chondritic to subchondritic (+1.9 to –4.4) and can be generated by 29% melting of the mantle metasomatized by 40% TTG- type melt, under oxidizing conditions, leaving a residue composed of orthopyroxene, garnet, clinopyroxene and magnetite. Meanwhile, the Ourilândia complex provided values of εHf(2.88 Ga) = +3.4 to –2.0 and its different varieties of granitoids (including quartz monzodiorite) were formed from 18–33% melting of the mantle enriched by 20–40% TTG-type melt, under oxidizing conditions, leaving a residue composed of orthopyroxene, clinopyroxene, garnet, magnetite ±olivine. The mafic enclaves and the quartz diorite show distinct petrogenetic histories and were assumed to be a product of partial melting from the mantle metassomatized by fluids at lower pressures, outside the garnet stability zone. (3) The equigranularmonzogranite represents the largest unit in the area and was correlated with the Boa Sorte batholith (Canaã dos Carajás granitic suite). Its parental magma can be formed by 18% melting from a TTG-type trondhjemite (analogous to those of Água Azul do Norte) under relatively oxidizing conditions, leaving a residue composed of plagioclase, quartz, biotite, magnetite and ilmenite. The U-Pb data allowed to distinguish four zircon populations (3.04 Ga, 2.97 Ga, 2.93 Ga and 2.88 Ga). The youngest population was interpreted as the magmatic crystallization age (coeval to the Ourilândia complex) and provided subchondritic values of εHf(2.88 Ga) = –0.8 to – 4.1, which confirms its crustal origin. The 2.93 Ga population was interpreted as crystals C inherited from the TTG-type source and provided chondritic εHf(2.93 Ga) = +2.8 to –0.7 (Hf-TDMC = 3.1–3.4 Ga), indicating a shorter crustal residence time than the 2.88 Ga population (Hf-TDMC = 3.3–3.5 Ga). The populations dated at 3.04 Ga and 2.97 Ga were interpreted as xenocrystals with εHf(3.04 Ga) = –1.7 to –2.2 (Hf-TDMC = 3.5 Ga) and εHf(2.97 Ga) = +1.4 to –5.7 (Hf-TDMC = 3.3–3.7 Ga), respectively. (4) The high-Ti porphyritic granodiorite and the associated heterogranular monzogranite are closely related to the Boa Sorte granite and were grouped in the Tucumã granodiorite-granite suite, which has affinity with the Closepet (Dharwar craton, India) and the Matok (Pietersburg block, South Africa) granites. The high-Ti granodiorite can be formed by 30% melting from the mantle enriched with 40% of TTG-type melt under oxidizing conditions, leaving a residue composed of orthopyroxene, olivine, plagioclase, clinopyroxene and magnetite, with the participation of a component enriched in HFSEs, such as sediments, fluids and/or asthenosphere materials. The petrogenesis of the monzogranite of this suite involved mixing between 40% crust-derived magmas (Boa Sorte granite) and 60% enriched mantle-derived magmas (high-Ti granodiorite). A three-stage tectonic model is assumed to explain the C origin and isotopic signature of the studied granitoids. In general, the Hf-TDMC ranging from 3.7 to 3.1 Ga, indicating the existence of a Paleoarchean crustal component, which was generated in long-lived dome-and-keel tectonics (~600 Ma) and later recycled in the mantle allowing its enrichment from low-angle subduction in Mesoarchean (2nd setting), where the TTG-type granitoids and the first sanukitoid generation were formed at 2.92 Ga. Then, a short-lived collision (3rd setting) defined by the peak regional metamorphism (2.89–2.84 Ga) and associated with crustal thickening and slab breakoff allowed the origin of large volumes of mantle- and crust-derived magmas at ~2.88 Ga, where the ascent and emplacement were conditioned by shear zones.