2020-03-052020-03-052019-12-18SANCHES NETO, Silvio. Petrologia magnética da associação gabronorito charnoquitogranito de Ourilândia do Norte (PA), Província Carajás. Orientador: Davis Carvalho Oliveira.2019. 56 f. Trabalho de Curso (Bacharelado em Geologia) - Faculdade de Geologia, Instituto de Geociências, Universidade Federal do Pará, Belém, 2019. Disponível em: https://bdm.ufpa.br/handle/prefix/3081. Acesso em:.https://bdm.ufpa.br/handle/prefix/3081This work investigates the formation conditions (T, fO2 e xH2O) of the gabronorite-charnockite-granite association of the Ourilândia do Norte region, based on the magnetic susceptibility combined with the study of the nature and textural aspects of opaque minerals. These rocks are intrusive to Mesoarchean leucogranites and sanukitoids (~2.88 Ga) and were subdivided into four petrographic groups: (i) gabronorite; (ii) orthopyroxene granodiorite; (iii) clinopyroxene monzogranite; and (iv) monzogranite amphibole. Its plutons are elongated in the NE-SW and E-W direction, where the main one is ~ 12 km long and 2-3 km wide. Overall, they show well preserved magmatic texture. However, they may exhibit deformation features such as planar weave formed by the preferred orientation of feldspars and mafic aggregates, with NE-SW or E-W direction and subvertical dip (70-80º). Magnetic susceptibility (SM) data allowed to differentiate these rocks into two magnetic populations (A and B). Population A is formed by gabronorite and pyroxene granitoids. They have the highest SM values (3.16x10-3 - 2.21x10-2 SIv) with modal content of opaque minerals ranging from 0.2 to 1.7% and important presence of magnetite and ilmenite, while hornblende monzogranite facies defines population B, characterized by lower SM values (2.31 x 10-4– 3.09 x 10-4), it shows lower opaque mineral content (<0.3%) and is characterized by the presence of zoned goethite. Opaque minerals found in both populations are represented by magnetite, ilmenite, martite, goethite, pyrite and chalcopyrite. The sequence of formation of opaque minerals indicates a progressive increase in the conditions of fO2 and xH2O, starting from the magmatic to the postmagmatic stage. This is consistent with high fO2 conditions between the FMQ and HM buffers above the NNO buffer. The relationship of these buffers with the average SiO2 contents allowed to estimate a temperature range between 820° and 690° C during the crystallization of these rocks. The interpretation of relatively high conditions for fO2 during the crystallization of these rocks is reaffirmed by the low Fe / (Fe + Mg) ratio values in biotite and amphibole, which indicate affinity with the magnetite series under intermediate to high conditions of fO2.Acesso AbertoPetrologia MagnéticaQuímica MineralCharnoquitoProvíncia CarajásCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIATrabalho de Curso - Graduação - Monografia