2019-02-262019-02-262015-04-30BARROS, Luisa Dias. Caracterização geológica da suíte ofiolítica Serra do Tapa, SE do Pará – Cinturão Araguaia. Orientador: Paulo Sergio de Sousa Gorayeb. 2015. 97 f. Dissertação (Mestrado em Geologia e Geoquímica) – Instituto de Geociências, Universidade Federal do Pará, Belém, 2015. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/10704. Acesso em:.https://repositorio.ufpa.br/handle/2011/10704In northern Araguaia Belt (CA) along its low-grade metamorphic domain, the region known as Serra do Tapa, between the municipalities of Sapucaia and Xinguara, SE Para exposes one of the largest CA ophiolite bodies interpreted as fragment of oceanic lithosphere the Araguaia basin in Neoproterozoic. The Suite Ophiolitic Serra do Tapa (SOST), denominade in this work, is a set of elongated bodies with a length of 48 km with preferential orientation in the direction N-S. It represents a dismembered ophiolitic sequence comprising serpentinized peridotites, massive and pillow basalts, volcanossedimentary rocks, iron formation and cherts. All this set embedded through thrust zones in the metasedimentary rocks of low metamorphic grade of Formation Couto Magalhães. The serpentinized peridotites have dark or light green, coarse-grained and represent the basal portion of the stratigraphic sequence suite. Originally, the peridotites were probably the harzburgite and dunites type. The harzburgites have protogranular texture, with a marked presence of pseudomorphic textures bastite type and mesh, which result from orthopyroxene transformations; and olivine to lizardite, respectively. The dunites have mesh predominant texture, with the presence of fine chromite grains dispersed in the matrix composed of serpentine (lizardite). The volcanic unit of suite represented by massive basalt submarine flows and pillow structures. The basalts occur as homogeneous flows, massive and in the upper portions feature marked for pillow structure, and locally, breccia flow surface (hyaloclastites). The pillows have a zoning, where in the core consists of massive basalt greenish brown color, aphanitic with intersertal texture composed of crystals of plagioclase, volcanic glass and Clinopyroxene. At the edge zone are present glassy basalts of yellowish green color, aphanitics and quenching textures ultrafast as spherulites, and radial acicular crystals of plagioclase, textures type "swallowtail" and hollow sections. The hyaloclastites occur in the outer zone of the pillow and represent breccias surfaces basaltic. Finally, basalt glass is dark green color of the surface flows (interpillow zone). The volcanossedimentary interface sequence is the interaction between the basalt flows and pelitic sedimentary rocks. The tuffaceous mudstone consists of a pelitic matrix with lytic fragments of metabasalt stretched and broken. The sedimentary portion of the suite consists of iron formation and cherts and represent the chemical sedimentation records in deep-sea ocean environment, is the upper portion of this ophiolitic suite. Another important feature is the presence of sinistral strike-slip shear zones and dextral of kilometric extensions with preferential orientation NE-SW and EW. All structures truncated by normal faults of NW-SE direction. The rocks of Formation Couto Magalhães evidence of metamorphism is most obvious in slates and phyllites (sericite and chlorite formation) in serpentinized peridotites occurs generation of non-superposition serpentine pseudomorphs of pseudomorphs, the massive basalts, the metamorphic association is defined by ab + Tr act + Cl + Ep ± Stp; the paragenesis of these rocks indicate metamorphic transformation in greenschist facies low. For lithochemical studies were prioritized portions of the core of the pillow, which remained in many cases, the protected metasomatic transformations. Divergent data in some samples can be explained because they are samples closest to the edges of the pillows, which suffered intense transformation due to oceanic metamorphism. Geochemically, the basalts show subalkaline nature, tholeiitic compatible with the MORB type. Sr negative anomalies may indicate plagioclase retention during partial melting events from depleted mantle source. The ETR diagram shows slightly depleted behaviors of LREE and enriched in heavy REE and smooth Eu anomaly; and this pattern confirmed the reasons (La / Yb) N and (La / Sm) N <1 magmas also point to the N-MORB type. The evolution of the suite is on the development of oceanic Araguaia Basin with the generation of an old oceanic lithosphere to rise and perhaps upper mantle exposure, volcanism forming the deep ocean substrate and sedimentation (tuffaceous mudstone, banded iron formation and cherts). Later detachment processes of the substrate crust / mantle led to the tectonic inversion of the sequence, leading to compressional tectonic phase, which led to obduction of ophiolite bodies, generating a late thrust and transcurrent system with movement toward the Amazonia Craton, segmented the ophiolite bodies and mixing them with rocks Couto Magalhães Formation accompanied by regional metamorphism of greenschist facies low.Acesso AbertoSudeste PetrologiaSerra do TapaCinturão AraguaiaPetrologia - Pará, SudesteSuíte OfiolíticaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA::MINERALOGIAPETROLOGIA E EVOLUÇÃO CRUSTALGEOQUÍMICA E PETROLOGIA