Vilalva, Frederico Castro JobimOliveira, Armando Lucas Souza de2020-02-132021-09-202020-02-132021-09-202019-12-13OLIVEIRA, Armando Lucas Souza de. Elpidita, um álcali-zirconossilicato do Plúton Papanduva (PR-SC): aspectos texturais, quimismo e implicações petrológicas. 2019. 89f. Trabalho de Conclusão de Curso (Graduação) - Curso de Geologia, Departamento de Geologia, Universidade Federal do Rio Grande do Norte, Natal, 2019.https://repositorio.ufrn.br/handle/123456789/34366The Papanduva Pluton (Morro Redondo Complex, South Brazil) comprises an association of peralkaline rocks which includes the most evolved types within the Graciosa A-type Province (S-SE Brazil). Alkali-feldspar granites from this pluton host typical miaskitic and agpaitic mineral assemblages that can be identified based on their main Zr-bearing minerals (zircon and alkali-zirconosilicates, respectively). Elpidite (Na2ZrSi6O15.3 H2O) is the most prominent alkali-zirconosilicate described in the Papanduva Pluton, and its crystallization occurs during late- to post-magmatic stages. This work deals with the textural and compositional aspects of the elpidite from Papanduva Pluton. Mineral identification was conducted based on X ray diffraction data and optical properties, and corroborated by the chemical compositions. Elpidite crystalizes in two textural groups: subhedral to euhedral crystal (EuC) and granular aggregates (GAg), with no significant chemical variation between them. Conversely, two contrasting chemical groups were identified (Elp1 and Elp2), despite the textural differences. Elp1 represents a high-Zr group (with lower Na and Si), comparing to Elp2. Ca contents are invariably low. This distinction can be partly explained by chemical competition between elpidite and aegirine, which contains high contents of Zr. Trace and rare earth elements patterns for elpidite and zircon reveal that theses minerals are the main sinks for heavy REE and HFSE (specially Zr, Hf and Y) in the Papanduva granites. The main controlling factor on the admission of REE, Y and U into the structures of zircon and elpidite is the activity of alkali metals; whereas O2 fugacity influences the behavior of Zr, Hf and Th. The composition of zircon and elpidite types allowed to recognize three distinct moments in the crystallization sequence that register increasing peralkalinity and oxidation along the miaskitic-to-agpaitic transition. Furthermore, the occurrence in these rocks of K-rich zirconosilicates, for which scarce information are available, and are mostly produced through elpidite destabilization, suggest a noticeable increase in K2O activity at post-magmatic stage. This feature allows to infer on the influence of a possible (auto?)-metasomatic, potassic fluid.ElpiditaTransição Miasquítica-AgpaíticaPlúton PapanduvaProvíncia GraciosaElpiditeMiaskitic-to-Agpaitic TransitionPapanduva PlutonGraciosa ProvincebachelorThesis