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Repositório Científico do Laboratório Nacional de Energia e Geologia
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Insights into rare earth elements and other critical raw materials from Castelo Branco massif alluvial deposits (Portugal)
Publication . Salgueiro, Rute; Silva, Teresa; Martín-Méndez, I.; de Oliveira, Daniel Pipa Soares; Batista, Maria Joao; Inverno, Carlos
ABSTRACT: Actual and future demands for critical raw materials and strategic raw materials (CRM/SRM) justify the global search for their potential sources and the exploration approaches to reach them. This study discloses the characterization of rare earth elements (REE) and other CRM-bearing alluvial heavy minerals samples sourced from the late- to post-tectonic Variscan Castelo Branco Massif (Portugal). It also contributes to an understanding of REE, Th, and U anomalies from local and correspondent stream sediments identified in past geochemical surveys. The alluvial samples were subjected to semiquantitative analysis of their minerals under a binocular microscope and to chemical analysis through portable X-ray fluorescence. A varied mineralogical association and a geochemical fingerprint compatible with their main granitic source was identified, revealing several minerals that carry CRM, in which REE and titanium minerals stood out. The titanium minerals have the higher average abundance (54%), being ilmenite-dominant (50%), as supported by the relatively higher Ti content of these samples (up to 28.88%). The REE minerals occur as accessories and have a summing average of 12%, in which monazite is the most abundant (4.97%). Geochemical data support alluvial monazite as the mineral with the highest REE and Th concentrations, as described in the literature on its granitic source. In addition, the magnetic fraction of samples (∼85%) that includes monazite and xenotime presents LREE anomalous contents (up to 4,557 mg/kg) in relation to their granitic source, NASC, and even to ΣREE anomalous values revealed by local stream sediments. The Th (up to 1,969 mg/kg) and U (up to 244 mg/kg) contents follow the same trend. Nevertheless, the nonmagnetic mineral fraction that includes apatite and zircon reaches higher U contents (up to 448 mg/kg). This study indicates that the SRM Ti (ilmenite) and LREE (monazite) have the potential to form placer deposits sourced from Castelo Branco granitic rocks in a wider area, which is supported by the regional Ti placers exploited in the past. The occurrence of other accessory elements/minerals with industrial applicability associated with those placers may also represent future added value.
From waste to circularity: the potential of different treatments of poultry manure and forestry residues in a hot-spot production region in Portugal
Publication . d'Espiney, Ana; Verworner, Bengt; Pinheiro, Helena; Isabel, Marques; Oehmichen, Katja; Engler, Nils; Majer, Stefan; Stinner, Walter; Thrän, Daniela
ABSTRACT: Purpose The management of biogenic residues in a way that extends the lifetime of carbon within the systems is a focus of the present work. Different waste management systems are assessed in terms of GHG emissions and removals, aiming to identify that with the lowest impact on climate change. Methods A life cycle comparative analysis is performed, assessing the mitigation of the impact on climate change of the current waste management system (A) of the top two residues of a Portuguese region – composting of poultry manure and open air burning of forestry residues – considering two bioenergy solutions: biochemical conversion of poultry manure and thermochemical conversion of wood residues (B); biochemical conversion for both residues together (C), implying fungal pre-treatment of the wood residues, which adds a food product to the supply chain. Data were retrieved from literature and from authors’ experimental work. Assumptions underlying the methodological framework (e.g., cut offs inherent to comparative assertions) are discussed. A sensitivity analysis covers uncertainties underpinning bioenergy systems assessments (e.g., unperfect substitution and rebound effect phenomena). Results and discussion The highest impact on climate change is observed with system A, greenhouse gas (GHG) emissions 2 to 3 times higher than those of the other two systems. System A also performs poorly in conserving the biomass, e.g., forestry residues burning results in carbon being directly released to the atmosphere with no valuable intermediate use. In the base scenario, system B results in the lowest GHG emissions of the three systems, producing biochar, which contributes to carbon sequestering, and biodiesel. Nevertheless, system C can result in the lowest GHG emissions, in a scenario considering unperfect substitution with renewable sources being selected to match the biodiesel supply of system B. Conclusions System A is least preferable among the three options. Between systems B and C, ranking depends on whether unperfect substitution is considered. System B performs better in all scenarios, except with unperfect substitution, where
system C outranks B. Moreover, system C achieves a higher yield of digestate, a product providing other ecosystem services. Thus, in future research, the inclusion of other impact categories in LCA can reveal a better overall environmental performance for system C.
New Contributions to Mineralogical and Geochemical Knowledge of Old Preguiça Mine, Beja, Portugal
Publication . Silva, Teresa; Morais, Igor; Mesquita Soares, Sofia; Rodrigues, Ivo; de Oliveira, Daniel Pipa Soares; Mirao, Jose
ABSTRACT: Abandoned mining areas provide valuable opportunities to investigate ore-forming processes, supergene mineral transformations, and the geochemical behaviour of metals. In this sense, the old Preguiça mine (Beja, Portugal), exploited for Fe–Zn–Pb, was studied providing new mineralogical and geochemical data aimed at improving the understanding of the secondary mineral assemblages of this deposit. A total of 70 samples collected from three accessible underground levels (first, second and third) and mine waste, complemented by 16 samples from a deeper level (fourth) previously collected, were analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and a portable X-ray fluorescence (pXRF) equipment. Mineralogical phases are dominated by a wide range of secondary oxides, carbonates, arsenates, vanadates, silicates, phosphates and sulphates, but remnants of primary sulphides were also found. The following minerals can be emphasised: goethite, hematite, calcite, dolomite, descloizite, willemite, mimetite, cerussite, smithsonite and fraipontite. The presence of massicot in the Preguiça mine, is described for the first time. Bulk geochemical analyses show high concentrations of Fe, Ca, Zn and Pb, consistent with the observed mineralogy. The presence of vanadium- and arsenic-bearing minerals highlights the occurrence of critical raw materials, supporting the importance of reassessing other abandoned mining areas in the context of sustainable resource management and strategic raw-material planning.
A segurança geológica como gargalo para a infraestrutura, transportes e habitação nas cidades diante das mudanças climáticas
Publication . Rodrigues, I. R.; Dutra, A. C. D.; Santos, A. C.
RESUMO: As mudanças climáticas têm ampliado a ocorrência de eventos extremos, como chuvas intensas, deslizamentos e inundações, afetando principalmente áreas urbanas e infraestruturas vulneráveis. Este artigo discute a segurança geológica como um dos principais gargalos na sustentabilidade das cidades brasileiras, impactando diretamente os setores de infraestrutura, transportes e habitação. A partir de uma abordagem analítico-interpretativa e revisão bibliográfica, analisam-se os entraves técnicos, institucionais e sociais que dificultam a prevenção de desastres. Os resultados indicam que a ausência de mapeamentos de risco atualizados, a falta de comunicação com as comunidades e a integração entre os setores
dificultam a implementação de ações preventivas. Ressalta-se que, diante dos eventos extremos, é comum que as rotas de acesso e evacuação sejam obstruídas, comprometendo a resposta a emergências. Conclui-se que a integração entre conhecimento geocientífico, planejamento urbano e participação comunitária é fundamental para fortalecer a resiliência urbana.
Natural Hydrogen Prospectivity in Portugal: A first approach
Publication . Portillo, Juan C. C.; Ferreira, Pedro Tavares; Sampaio, José; Batista, Maria Joao; Represas, Patricia; Ramalho, Elsa; Machado, Susana; Carvalho, João
ABSTRACT: This works presents the first maps of the prospectivity of natural hydrogen in continental Portugal and the methodological approach undertaken. The methodology used in this study follows the Chance of Sufficiency (COS) approach, which is also sometimes referred as the Chance of Success in exploration geoscience. It is a probabilistic estimate of whether a geological prospect contains a resource (e.g., hydrocarbons, hydrogen, etc.) in sufficient quantity and quality to be considered a "success" or explorable. It is typically expressed as a percentage and reflects the likelihood that all critical geological factors align to yield a viable accumulation. COS is grounded in Bayesian probability and statistical modelling. It is often calculated by multiplying the probabilities of independent geological favourable factors, such as sources (presence of a generating system), reservoirs (porosity and permeability), seals (cap rock to trap fluids), trap (structural or stratigraphic configuration), timing and migration (alignment of generation and trap formation). In this study only the first three were considered (i.e. sources, reservoirs, and seals). Consequently, this work should be seem as a first approach for the prospectivity of hydrogen mapping in Portugal.