2020-01-102020-01-102013-09PAIVA, Hanna Paula Sales. Estudo petrográfico e geoquímico das formações ferríferas e rochas associadas da mina pedra branca do Amapari (Amapá). Orientador: Raimundo Netuno Nobre Villas. 2013. 72 f. Trabalho de Curso (Bacharelado em Geologia) - Faculdade de Geologia, Instituto de Geociências, Universidade Federal do Pará, Belém, 2013. Disponível em: https://bdm.ufpa.br/jspui/handle/prefix/2740. Acesso em:.https://bdm.ufpa.br/jspui/handle/prefix/2740The Mina Pedra Branca do Amapari is located about 18 km SE of the Serra do Navio town, Amapá state. Iron ore has been extracted from it as part of the banded iron formations that belong to the Paleoproterozoic Vila Nova Metamorphic Suite (VNMS). This study aimed not only to characterize petrographically and chemically these formations, as well as the associated rocks, but also to estimate the conditions under which the whole rock pile was metamorphosed and record possible evidence of hydrothermal activity in the mine area. Based on mineralogical and textural data of selected samples, three main lithological varieties were recognized, for what SEM-EDS and X-ray diffraction techniques played an important role: a) banded iron formation (BIF); b) schists; and 3) calc-silicate rocks, the former divided into itabirites and amphibole-bearing BIF. Several mineralogical associations could then be defined: quartz – hematite – magnetite ± apatite ± pistacite ± hercynite ± garnet, quartz – hematite – magnetite – actinolite ± pistacite ± apatite and actinolite – microcline – biotite – diopside – quartz – hematite – magnetite ± titanite, respectively for itabirites, amphibole-bearing BIFs and schists, in addition to actinolite – quartz – hematite – magnetite ± pistacite, diopside – actinolite – calcite – quartz - hematite – magnetite ± hercynite and diopside – magnetite – quartz - hematite for the calc-silicate rocks. These parageneses are consistent with derivation from both chemical and clastic sedimentary rocks, which deposited on a passive shelf environment and were subsequently subjected to the epidote-amphibolite facies conditions of the regional metamorphism. The presence of hercynite is indicative that the high pressure environment of this facies may have been reached, so that ranges of 7-10 kb and 500-650oC could be plausible. As far as the protoliths are concerned, the BIF’s were most likely derived from iron-rich and siliceous chemical sediments produced by exhalative fluids. In case of the amphibole-bearing BIFs these sediments may have been contaminated by carbonate material. Schists and calc-silicate rocks had as possible protoliths feldspathic greywackes with carbonate-pelitic matrix and marls, respectively. Chemically, BIFs, schists and calc-silicate rocks can be easily distinguished in terms of SiO2, Fe2O3(t), CaO and MgO,which are the main components of these rocks and reflect the abundance of quartz, hematite, magnetite, actinolite and diopside. In particular, schists are the rocks richer in K2O and TiO2 due to the significant amounts of micriocline, biotite and titanite they present. The chemical discrimination can also be made on the basis of selected trace elements. The BIFs are enriched in Sr, Ni, V and Cr, and impoverished in Co comparatively to the other rocks. Considering that some of these elements show low mobility in the supergene envirnment, they could help in mapping lithological units in very weathered and outcrop-scarce areas. Quartz and calcite veins/veinlets are important records of hydrothermal activity in the mine area after the metamorphism. Other remarkable hydrothermal products are the Mn-rich material deposited along NW-SE-trending shear zones.Acesso AbertoPetrologiaFormações Ferríferas BandadasRochas calciossilicáticasFácies epidoto-anfibolitoDiscriminação químicaMina Pedra Branca do AmapariCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIATrabalho de Curso - Graduação - Monografia