2023-02-032023-02-031987-07-01GASTAL, Maria do Carmo Pinto. Maciço granítico Musa: mapeamento,petrologia e petroquímica, Rio Maria, SE do Pará. Orientador: Roberto Dall' Agnol. 1997. 327 f. Dissertação (Mestrado em Geoquímica) - Curso de Pós-Graduação em Geociências. Núcleo de Ciências Geofísicas e Geológicas, Universidade Federal do Pará, Belém, 1997. Disponível em: http://repositorio.ufpa.br:8080/jspui/handle/2011/15255. Acesso em:.https://repositorio.ufpa.br/handle/2011/15255The Musa granitic massif, located in the extreme-southeast of the state of Pará (southern portion of the Mineral'de Carajás Province), is a permissive intrusion, placed in shallow crustal levels. It cuts rocks from the regional basement, formerly included in the Xingú Complex, including the Rio Maria granodiorite, the Pedra Preta greenstone belt type sequence and the Archean gneisses. Pre-existing faults and fractures played an important role in placing the massif. There are important wolframite mineralizations in quartz veins, adjacent to the granite, where it cuts the greenstone-like sequence, in the Pedra Preta area (to the west). Its origin is due to the thermometamorphic reworking of the W contained in the rocks of the greenstone sequence, at the time of the intrusion of the Musa massif. The contact relationships with the host regions reveal a high viscosity contrast between the granitic magma and the same, and that conditions of medium degree metamorphism and pressures below 4 kbar were reached. The faciology of the massif includes leucocratic to hololeucocratic biotite granites, containing amphibole and titanite, which were divided into monzogranites and syenogranites, and intermediate and acidic hypoabyssal rocks (microdiorites, porphyry dacites and porphyry granites). The relationships between the different facies indicate that the monzogranites are the most precociously placed, being cut by the dykes and both, in turn, truncated by the syenogranites. In monzogranites, the existence of enclaves of monzo to granodiorite composition is common, interpreted as crystalline residues carried in equilibrium by the magma. Texture and mineralogical variations observed in the two groups of granitic facies allowed us to subdivide them into seven distinct petrographic facies: Biotite-amphibole monzogranite, amphibole-biotite monzogranite, biotite-monzogranite, leucomonzogranite, amphibole-biotite syenogranite, leucosyene-granite and microsyenogranite. Some granitic rocks that occur associated with the mineralized veins of Pedra Preta resemble heterogranular leucosyenogranitic facies, laughing because they are more intensely transformed by late-magmatic events. The different granitic facies exhibit sub-alkaline composition, are calc-alkaline, metaluminous to slightly peraluminous and are relatively enriched in Si02, K20, FeO(t), Ti02, P205, Ba and Y and depleted in MgO. Together, they show greater analogies with the Cordilleran granites (type I - Chappell and White, 1974) or the Magnetite series (Ishihara, 1981), although the terms of hololeucocratic syenogranites differ a little from the others. According to the classification by Pearce et alii (1984) , they are classified as intraplate granites, developed in attenuated continental crust. The behavior of the trace elements does not characterize the different facies as metallogenetically specialized granites, however some samples of microsyenogranites can be seen as such. Geochronological data, Rb/Sr in T.R., obtained for the different facies present in the Musa massif, although not entirely conclusive, seem consistent with the observed order of placement. On the other hand, the given age, taking the set of samples from the various facies, is 1692 ± 11 Ma and R.I. 0.78777 : 0.00023. This age shows that this massif is not related to the Uatumã event, bringing it closer to the Jamon massif intrusion (1601 ± 21 Ma). The chemistry of the hypoabyssal rocks does not confirm their relationship with the volcanic ones of the Uatumã group. The "trend of tholeiitic affinities" in the AFM diagram, presented by the set of samples from the massif differs from that of the "calci-alkaline" of the Uatumã volcanoes. The spatial and temporal proximity between the Musa and Jamon massifs and the presence in them of very similar monzogranitic facies leads to the interpretation that they originated and evolved through analogous processes. This allows the definition of Acidic and Intermediate Magmatism of Rio Maria from the Middle Proterozoic (1700-1600 Ma), including the two massifs, intermediate and acidic hypoabyssal rocks and Marajoara granite. The dataset confirms the cogeniticity of the various facies occurring in the massif, but reveals possible variations in the source rocks. , which would be mixed. The expansion of partial melting processes led to the inclusion of more superficial rocks, related to volcanic sedimentary sequences. This model, coherent with the ideas of Hildreth (1981), reveals the existence of, at least, two slightly different magmatic liquids (monzogranitic and syenogranitic), formed at different depths of the crust and which would have evolved independently, but through of prolonged fractional crystallization processes. Regarding the tectonic environment at the time of generation of the Musa massif, the data leave doubts as to whether it is an intraplate, anorogenic granite or whether it is related to a Proterozoic continental margin.Acesso AbertoAttribution-NonCommercial-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nc-nd/3.0/br/Geologia regionalPetrologiaPetroquímicaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIAPETROLOGIA E EVOLUÇÃO CRUSTALGEOQUÍMICA E PETROLOGIA