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ResumoNo município de Boquira, interior do Estado da Bahia, funcionou durante aproximadamente 30 anos uma mineração de chumbo. O rejeito do processo de beneficiamento do minério foi depositado de forma inadequada próximo à cidade, e lá permanece até hoje. Este estudo tem como principal objetivo investigar a presença de chumbo em amostras do resíduo presente na antiga bacia de rejeito e identificar as fases minerais carreadoras desse elemento. Foram coletadas sete amostras em diferentes pontos da antiga bacia de rejeito e no seu entorno próximo à cidade. As amostras foram caracterizadas através de difratometria de raios X (DRX), microscopia eletrônica de varredura (MEV/EDS) e análise química por fluorescência de raios X (FRX). As análises químicas indicaram a presença de chumbo em todas as amostras analisadas e revelaram que o elemento se encontra concentrado nas frações de granulometria fina. Os resultados obtidos por difração de raios X mostram que o chumbo ocorre principalmente nas estruturas de anglesita, cerussita, galena, fosfohedifano e piromorfita. A partir das análises por MEV/EDS foi possível constatar que os principais minerais carreadores de chumbo se encontram em avançado estágio de intemperismo, eventualmente alterando para óxido de chumbo. A disposição inadequada desse tipo de rejeito pode vir a implicar em condições favoráveis para a liberação do chumbo da estrutura de seus minerais carreadores e consequentemente colocar em risco o meio ambiente e a população que vive no entorno da bacia de rejeitos. Palavras-chave: Mineração; Rejeito; Boquira AbstractBoquira is a city located at Bahia state where a lead mine operated for about 30 years. The tailings from the ore beneficiation process were improperly deposited close to the city and, unfortunately, they linger until nowadays. This study aims to examine carefully how the lead has been distributed along the tailing piles and to identify the mineral phases containing this element. In order to get the results, seven samples were collected from different points of the old tailings basin and its surroundings near the town. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM/EDS), and chemical analysis by X-ray fluorescence (XRF). The chemical analyses point out the presence of lead in all analyzed samples, being concentrated in fine grained fractions. X-ray diffraction results indicate that the lead occurs mainly associated with anglesite, cerussite, galena, phosphohedyphane and pyromorphite. From MEV/EDS analysis it was possible to observe that the minerals of lead are altered, even forming lead oxides. The improper disposal of this waste endangers the environment and the people living in that area. Estudos preliminares (Alves, 2014;Alves & Bertolino, 2013;Bertolino et al., 2014) discutem aspectos gerais da mineralogia do material presente na bacia de rejeitos, entretanto há uma certa escassez de trabalhos referentes à caracterização mineralógica detalhada do material que, do ponto de vista ambiental, se encontr...

Fluorapatite with monazite-(Ce) and xenotime-(Y) microinclusions occurs in the lithium–caesium–tantalum pegmatite body A of the Volta Grande mine, Minas Gerais state, Southeast Brazil. The fluorapatite displays faint zoning, detected mainly by cathodoluminescence. Electron probe and laser ablation analyses indicate that zoning in the fluorapatite corresponds to variation in Mn and rare-earth element (REE) content. Such compositional variation is attributed to partial removal of the REE from the fluorapatite structure during a dissolution–reprecipitation process, forming monazite-(Ce) and xenotime-(Y) microinclusions in the REE-depleted zones of the fluorapatite. These inclusions exhibit an inherited geochemical signature, manifested by low Th and U concentrations when compared to monazite and xenotime crystallised from melts. Rhodochrosite and calcite inclusions are also associated with monazite-(Ce) and xenotime-(Y) and are probably products of the same process, recycling Ca, Mn, and CO32− from the fluorapatite through the following reaction: [Ca(5–2a–b–½x),Naa,(Y + REE)a,Mnb][(PO4)3–x(CO3)x(F)] + Fluid[a(2Ca2+ + P5+) + (x–b)(Ca2+) + H2O)] → [Ca5(PO4)3(F,OH)] + a[(Y + REE)PO4] + b[Mn(CO3)] + (x–b)[Ca(CO3)] + Fluid a[Na+].On the basis of new fluid-inclusion analyses, we propose that a hot (T > 204.5°C), salty (16 wt.% eq. NaCl, attributed to LiCl), hydrous fluid mediated the dissolution–reprecipitation of the fluorapatite. This fluid corresponds to similarly described Li-rich fluids which were suggested to have re-equilibrated the mineralogical assemblage at the Volta Grande mine.

The pegmatites of the São João del Rei Pegmatitic Province are related to the Siderian protoliths of the Cassiterita and Resende Costa orthogneisses and to the Ritápolis metagranitoid of Ryacian age. Chemical analysis of garnet from twelve pegmatites reveal two different types of grains, which were found in the same pegmatitic body in six of these samples. One garnet type has almandine-spessartine composition (Sps 11.7-58.8 Alm 36.8-86.5 Prp 0.1-4.1 Grs 0.0-1.4 Adr 0.0-2.6), grains with orange and pink tones, and scarce mineral inclusions. These garnet grains may have been formed at the magmatic stage of pegmatite crystallization. The composition of these grains plot exclusively on the Alm-Sps axis at the Prp+Grs+Adr+Uvr × Alm × Sps diagram, as expected from garnet crystallized in pegmatites, and an expansion of the field associated to pegmatites is proposed. The second type has a distinct chemical composition (Sps 26.