Gaspar, Luís Miguel Guerreiro Galla, 1968-Ferreira, Bruno Filipe Farinha2024-02-192024-02-1920232023http://hdl.handle.net/10451/62727Tese de mestrado, Geologia (Geoquímica Mineralogia e Petrologia), 2023, Universidade de Lisboa, Faculdade de CiênciasAldeia’s pegmatite swarm, part of the much larger Barroso-Alvão pegmatitic field, is composed of several spodumene-bearing aplite-pegmatite bodies hosted in a sequence of micaschists and quartzschists belonging to the parautochthonous unit of NE Iberia. An appraisal of the Li-mineralization was carried out on drillhole samples from both host-rocks and aplite-pegmatite bodies. 30 thin sections were produced. After a detailed petrographic analysis, 17 thin sections were selected for EMPA to assess mineral compositions. The petrographic analysis revealed that spodumene-bearing aplite-pegmatites are poorly zoned, and show a complex mineral assemblage developed along two main crystallization stages (Stage I and Stage II), with a superimposed later metasomatic event. Given the metallogenetic and economic implications of the reported variability for the Libearing phases within the Barroso-Alvão pegmatitic field, it is important to stress that: 1- although usually deformed, analysed spodumene is extremely fresh, with no evidence of alteration or weathering processes; 2- petalite is absent and there is no suggestion that spodumene results from the decomposition of petalite, since SQI textures are inexistent in studied samples. All the main mineral phases from both stages (including spodumene) exhibit micro-textures and intra-crystalline high-T deformation features, suggesting deformation under crystallization and cooling conditions, compatible with the regional Variscan deformation patterns observed in the metasedimentary host-rocks. Based on petrography and mineral chemistry, the studied Aldeia aplite-pegmatites can be classified as Complex Spodumene Rare Element-Li pegmatites. They are texturally and compositionally similar, showing a complex history with two main crystallization stages, with secondary phosphates underlining late metasomatism. From a geochemical standpoint the system stands out due to elevated enrichments in Na. Stage 1 should represent a Li-poor melt, with moderate P and F, and minor Fe, Mn, and Sn. Stage 2, concomitant with spodumene crystallization, should represent a Li-rich and F-poor melt with minor Nb and Ta.engLitioEspodumenaAplito-PegmatitoPortugalElementos-RarosTeses de mestrado - 2023master thesis203525230