The Orosirian of SE Amazonian Craton is mainly characterized by igneous associations from I, A and rare S types outcropping from west to eastward, in the Tapajós, Iriri-Xingu and Carajás domains. The Carajás domain represents the oldest crustal region, stabilized during the Neoarchean. The Tapajós domain represents, at least to some extent, the proximal region of a continental margin actived during the Orosirian. The Iriri-Xingu domain (IXD), at the center, still holds an uncertain tectonic role. These igneous associations were formed in multiple magmatic episodes through this geological period, which can be temporally divided in three intervals. The first interval, from 2030 to 2000 Ma, is marked by a juvenile, I-type, calc-alkaline volcano-plutonism in the Tapajós domain. The second interval, from 2000 to 1960 Ma, is marked by a series of I type, high K calc-alkaline to shoshonitic rocks that expands from Tapajós domain to the east, in the IXD. The rocks of the third interval (1900 to 1860 Ma) are represented by an I type calc-alkaline magmatism and an A type magmatism, the later associated to mafic rocks. The A type rocks, typically from A 2 sub-type, belong to a broader geographical context than the I type magmatism, and outcrop in an expressive area through the Amazonian Craton (ca. 1,500,000 km 2 ). These rocks are generically attributed to the Silicic LIP Uatumã. In this thesis, we concentrate on the plutonic part of these associations and present new geological, lithochemical and isotopic (U-Pb, Lu-Hf in zircon and whole rock Sm-Nd) data for granites of the second and third magmatic episodes from central-eastern and northern IXD. In central-eastern IXD, the granites São Pedro do Iriri, Vila Primavera, Caboclo and Jabá present an alkaline to subalkaline, metaluminous to slightly peraluminous, ferroan to slightly magnesian character. The first three granites are akin to the reduced tin-specialized A type granites of Velho Guilherme Suite, from Carajás Domain. U-Pb and Lu-Hf data provided a crystallization age of 1897 ± 8 Ma for the São Pedro do Iriri Granite, and εHf (t) values (from -8.22 to -17.44) that point to a mixing of meso and paleoarchean crustal sources. The Jabá Granite exhibits geochemical affinity to the oxidized A type granites from Iriri-Xingu and Carajás domains. This granite yielded a U-Pb in zircon crystallization age of 1887 ± 14 Ma and εHf (t) values of -6.43 to -10.21, indicating a more radiogenic, homogeneous and predominantly mesoarchean crustal source. The classic I type calc-alkaline rocks studied in this work comprise the Rio Bala, Porto Estrela and other sparse granitic samples from Iriri river that represent, among others plutons, the Serra do Chavito and Pedra do O granites. They are amphibole and biotite bearing rocks that show magnesian, metaluminous, high K calc-alkaline to slightly shoshonitic character. The Porto Estrela Granite exhibits tonalitic to granitic facies and yielded a U-Pb age of 1972 ± 6.6 Ma. The samples of the calc-alkaline granites from Iriri river are quartz-monzonitic to granitic in composition. Samples from the Serra do Chavito and Pedra do O granites yielded ages of 1987 ± 6.6 and 1988 ± 8 Ma, respectively. The ages yielded by the Porto Estrela and the Iriri river’s granites correlate these rocks to the second interval volcano-plutonic association of Iriri-Xingu and Tapajós domains. The Rio Bala Granite is quartz-monzonitic and granitic in composition, exhibits a chemical trend typical of subalkaline rocks and yielded a U-Pb in zircon age of 1877 ± 8.2 Ma. This granite represents the first record of a high K calc-alcalic plutonism coeval to the volcanic rocks of the Iriri Group (1.88-1.87 Ga calc-alkaline rhyolite and dacite) in IXD. Chemically, it presents a more evolved character and affinity to the granitic facies of Parauari Suite. The remaining studied rocks of the central and northern IXD comprise two atypical samples of A type and I type granites, that represents respectively the Cachoeira do Julião and Igarapé Limão plutons. The A type granite sample is a cpx-hb-bt quartz-syenite. Its petrographical, chemical and previous geochronological data (1889 ± 3 Ma) allow a correlation with the plutonic rocks of the Uatumã SLIP. The other sample constitutes a biotite monzogranite of magnesian, slightly peraluminous, medium to high K calc-alkaline character, similar to the I type adakitic rocks. The REE curved upwards pattern and the relatively low Dy/Yb ratio (1.04) suggest residual amphibole or its fractioning in relatively high P in presence of garnet. The low contents of MgO, #Mg, Yb and Ni, and high FeO t /MgO ratio indicate an affinity to the adakites of thickened lower crust melting. The necessary conditions to this rock genesis are satisfied if we consider the IXD crust to be deformed and thickened in the Transamazonian Cycle and latter thinned in the Orosirian. The data related to the I type magmatism with ages of 2.00 to 1.96 Ga suggest an extensive but brief event, with a minimum area of 190,000 km 2 and lifespan of 40 M.y. Extrapolating modern geodynamical conditions for subduction to the Paleoproterozoic, it is concluded that the space-temporal pattern of this magmatism cannot be uniquely explained by subduction process. Therefore, it is inferred that at least part of this magmatism should be generated in a convergent margin by other process than subduction or, alternatively, a post-orogenic event. The same reasoning can be adequately projected to the 100 M.y. younger calc-alkaline rocks of the third time interval (1.90–1.86 Ga). The Nd isotopic data for the studied rocks present moderately to highly negative εNd (t) values and siderian to mesoarchean Nd-T DM model ages. The available data, presented in this work and from literature, reveal a heterogeneous crust, partly composed by a crust similar to the Carajás’. The neoarchean and siderian isotopic signatures could represent, in a non-mutually exclusive way: the presence of juvenile crustal segments; mixture of ancient archean crust and mantellic input (probably from Ryacian and/or Orosirian); or mixture of diverse crustal components. This crust could be interpreted as paleo to mesoarchean preserved nuclei bordered by reworked crust that probably underwent juvenile inputs on Ryacian and/or Eo-Orosirian, besides presenting isolated blocks/segments of juvenile Neoarchean and Ryacian rocks. Concerning the IXD lithostratigraphy, we suggest the Iriri Group to be composed by the Santa Rosa – acid A type volcanics - and Confresa – acid I type calc-alkaline volcanics – formations, both with crystallization ages within 1.90 and 1.86 Ga. We propose the 2.00 to 1.96 Ga calc-alcalic volcanic rocks, formerly related to the Iriri Group, to be grouped in the Jarinã Formation. We also recommend the adoption of the term Vila Rica Suite to refer the I type granites coeval to the Jarinã Formation. We also endorse grouping the A type granites akin to the oxidized granites of Carajás in the Rio Dourado suite. In respect to the potentially tin-specialized reduced A type granites, we recommend this group of rocks to be assembled in the proposed São Pedro do Iriri Suite.
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