DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Item Mesoarchean migmatites of the Carajás Province : from intra-arc melting to collision.(2021) Silva, Marco Antonio Delinardo da; Monteiro, Lena Virginia Soares; Santos, Ticiano José Saraiva dos; Moreto, Carolina Penteado Natividade; Sousa, Soraya Damasceno; Faustinoni, Jackeline Monteiro; Melo, Gustavo Henrique Coelho de; Xavier, Roberto Perez; Toledo, Benfica A. M.In the Carajás Domain, northern Carajás Province, Amazonian Craton, the oldest units encompass the Mesoarchean migmatites of the Xicrim-Cateté Orthogranulite and Xingu Complex. The Xicrim-Cateté Orthogranulite underwent early dehydration and late water-fluxed partial melting. The first process resulted in net-structured and schollen migmatites with a pargasite-bearing mafic granulite paleosome. The F-pargasite breakdown produced a neosome with peritectic enstatite, diopside, and plagioclase and a residual amphibole-free mafic granulite. The late water- fluxed partial melting generated quartzofeldspathic leucosomes in shear bands of the NW-SE-trending high-angle transcurrent shear zones. The Xingu Complex is composed of stromatic, net-structured, schollen and schlieren migmatites developed in the late water-fluxed partial melting event. These migmatites have orthogneiss and am- phibolite paleosome and syn-tectonic quartzofeldspathic leucosome and biotite-rich melanosome oriented along a low angle NE-SW to NW-SE gneissic foliation. The Xicrim-Cateté paleosome age remains undefined, but the U–Pb zircon ages of the pyroxene-bearing neosome constraint the dehydration-melting to c. 3.06–2.93 Ga. The εHf data (−2.2 to +1.2) of the neosome tie the dehydration-melting of the pargasite-bearing granulite to the underplate of mantle melts. The Zr-Ti-Y content and Ti/V ratios of the pargasite-bearing granulite suggest a compositional shift of their protoliths from MORB to IAT, characterizing a scenario of subduction installation and magmatic evolution. The Xicrim-Cateté pyroxene-bearing neosome is geochemically similar to the Xingu orthogneiss. Both rocks have a TTG affinity and similar εHf values (+0.8 to +1.6) and crystallization ages (2.94 Ga). It indicates a common source for them and suggests that the dehydration partial melting of the primitive mafic crust produced a signif- icant portion of the TTG felsic continental crust of the Carajás Domain. It probably occurred during the island-arc setting evolution between 3.06 and 2.93 Ga when supra-subduction mantle melts started to trigger the composi- tional differentiation of the mafic crust. The late water-fluxed partial melting was controlled by fluid influx into the structures developed during the regional deformation of the Carajás Domain at c. 2.89–2.85 Ga, likely associated with a collisional event in the Carajás Province.Item Neoproterozoic geotectonic evolution of Tocantins structural province central Brazil.(1999) Strieder, Adelir José; Suita, Marcos Tadeu de FreitasTocantins Structural Province (TSP) is the main tectonic feature in Central Brazil. It separates two main cratonic areas (former continental plates): the Amazonian Craton to the West and the São Francisco Craton to the East[ Recent geochronological data (U-Pb and Sm-Nd) and structural studies show that the actual structural framework of the province was developed during the Neoproterozoic. It is herein proposed that Brasiliano Orogenic Cycle in the TSP was developed in four broad tectonic stages: 1) an ocean opening stage began possibly 0169 Ma^ 1# an island-arc system development stage started 0999Ma and its amal! gamation lasted until ca[ 799 Ma^ 2 a continental collision stage began ca[ 799Ma with the accretion of the island!arcs to the upper Amazonian plate\ the closure of the Goiás Ocean and the development of a foreland basin upon the lower São Francisco plate^ and 4) a post-collisional stage (549-499 Ma) with the development of transcurrent faults (Transbrasiliano lineaments)\ back!thrust reverse faults\ and intrusion of alkalic granitic plutons.