Browsing by Issue Date, starting with "2023-07"
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- Litoteca do LNEG Aljustrel, um espólio científico fundamental para a investigação da Faixa Piritosa Ibérica e da Zona de Ossa-MorenaPublication . Matos, João Xavier; Morais, Igor; Santos, Sara; Gonçalves, Pedro; Batista, Maria Joao; de Oliveira, Daniel Pipa Soares; Dias, Ruben PereiraSUMMARY: Since 2018 the LNEG’s Aljustrel drill core shed is dedicated to the southern Portugal collections distributed by Iberian Pyrite Belt (IPB) and Ossa-Morena Zone (OMZ). The archive includes exploration drill hole cores, soil, stream sediments and rock samples, technical reports, and a complete and detail map collection (1/5.000 and 1/25.000 scales), all organized in databases. Drill hole relog allow a better understanding of the subsurface being essential in stratigraphy, structural mapping, mineral exploration and metallogeny. Following the regional Smart Specialization Strategy defined by CCDR Alentejo to Geological Resources, the LNEG Aljustrel develops R&D programs dedicated to thematic mapping and mineral resources. Critical Raw Materials mineralizations are present at the archives like IPB VMS Cu-Zn-Pb(Au-Ag-Sn-Sb) and Fe-Mn deposits and OMZ sulphide-magnetite (Zn-Pb,Cu(Au)), magnetite and Cu(Au) veins. The preservation of the subsurface geological heritage is critical to the IPB and OMZ research and an institutional LNEG mission.
- High-resolution P- and S-wave reflection studies of an intraplate structure: The Azambuja fault, PortugalPublication . Ghose, Ranajit; Carvalho, João; Alves, Daniela; Santos, Luiz Alberto; Ressurreição, Ricardo; Alves, Paulo Henrique Bastos; Leote, JaimeABSTRACT: The Azambuja fault is a NNE trending structure located 50 km north of Lisbon, the capital and most populous city of Portugal. The fault has been considered as a possible source for the historical, large earthquakes. Under-standing this fault is a priority in seismic hazard evaluation of this region. The fault has a clear morphological signature. Miocene and Pliocene sediments are tilted eastward and cut by steeply dipping mesoscale fault seg-ments, presenting reverse and normal offsets with a net downthrow to the east. Neotectonic studies indicate a Quaternary slip on the fault of 0.05-0.06 mm/year. However, no direct evidence of the Azambuja fault affecting the Pleistocene or Holocene sediments was found so far. Here, we present the findings from high-resolution seismic reflection studies using both P-and S-waves over the Holocene deposits. The detection of small-throw faulting in ductile sediments is a challenging task. We show that multiple signatures, like perturbations in the reflection hyperbolae visible in shot and CMP gathers, interruptions of reflectors in stacked sections, lateral seismic velocity variations obtained by horizon velocity analysis, all at coincident locations, strongly suggest that the activity of the Azambuja fault has affected the Holocene sediments in the study area. The lateral velocity variations are corroborated by wavepath eikonal traveltime tomography and velocity analysis supported by seismic modeling. By means of 2D viscoelastic modeling, we explain the absence of fault-related diffractions and negligible back-scattered energy from the fault. Using data from nearby boreholes, we find that the 15 ka old alluvium cover has indeed been disturbed by the presence of shallow fault strands. Considering the estimated vertical throws and the empirical relationships between fault length, co-seismic rupture and magnitude, a slip rate of 0.07 mm/y, slightly larger than previously thought, is expected for this fault.
- Early and Middle Jurassic palynostratigraphy of the Lusitanian Basin in the proto-Atlantic contextPublication . Correia, Vânia; Pereira, Zélia; Riding, James; Duarte, L. V.; Henriques, Maria Helena; Fernandes, PauloSUMMARY: A palinologia é uma ferramenta muito útil nos trabalhos de bioestratigrafia e interpretações paleoambientais, e que pode ser aplicada no conhecimento da geologia da Bacia Lusitânica. Assim, foi desenvolvido um estudo palinoestratigráfico de alta-resolução em 8 cortes do Jurássico Inferior e Médio (Sinemuriano superior—base do Batoniano) da Bacia Lusitânica e, neste trabalho, são apresentados os intervalos de ocorrência e bioeventos associados aos principais taxa identificados, nomeadamente no grupo dos quistos de dinoflagelados.
- Cultural Heritage analysis using Synchrotron Radiation: case studies in Ceramics, Glasses, and Lithologic MaterialsPublication . Veiga, JP; Coutinho, ML; Figueiredo, Elin; Silva, TeresaABSTRACT: Synchrotron radiaton is a powerful tool for non‐destructve analysis of materials in cultural heritage research. It has revolutonized our ability to understand the compositon, structure, and history of cultural heritage objects, leading to significant advances in fields such as archaeology, art conservation, and materials science. Dedicated beamlines for cultural heritage research are available at synchrotron facilites around the world, such as the European Synchrotron Radiation Facility (ESRF), SOLEIL synchrotron, and ALBA synchrotron, providing specialized support and instrumentation for high‐resolution analysis of cultural heritage objects using various techniques, such as X‐ray absorption spectroscopy, X‐ray fluorescence, X‐ray diffraction, and X‐ray imaging.
- Contribuição do método geofísico eletromagnético no domínio de tempo para o estudo dos sistemas aquíferos multicamada transfronteiriços da bacia do Kalahari, Cunene, AngolaPublication . Francés, Alain Pascal; Ramalho, Elsa; Santos, Fernando Monteiro; Llorente, J.; Mateus, T.; Cuervo, I.; Lobón, Jose Luis Garcia; Dala, V.; Ditutala, M.; Victorino, Américo da MataSUMMARY: Under the scope of project PLANAGEO, a geophysical survey using the time domain electromagnetic (TDEM) method was planned and conducted. This survey aimed to contribute to the hydrogeological conceptual model of the KOS and KOH aquifer systems, to validate the 1960 data electrical resistivity reprocessing and to define the future location of deep boreholes. The TDEM survey allowed identifying different layers with different geoelectric characteristics and assigning electrical resistivity characteristics to each hydrogeological feature of the aquifer systems. These assumptions were found adequate, and the results were used to define the drilling locations of 5 wells.
- STTF 100 : Memória descritiva : energia e comunicaçõesPublication . Azevedo, PedroABSTRACT: A Solar Tower Testing Facility – 100 (STTF-100) é uma infra-estrutura experimental que consiste num concentrador solar do tipo sistema de receptor central, também designado por torre solar, e que ocupa uma área total de aproximadamente 725 m2. Esta instalação encontra-se localizada no campus do LNEG em Lisboa.
- Áreas potenciais de Portugal para recursos minerais do domínio públicoPublication . Carvalho, Jorge; Filipe, Augusto; Gonçalves, Pedro; Lisboa, Jose; Matos, João Xavier; Batista, Maria Joao; Salgueiro, Rute; de Oliveira, Daniel Pipa SoaresSUMMARY: Land-use planning is decisive for granting access to mineral resources. During the work to identify the actions to be taken for preparing the National Strategy for Geological Resources, a map of mineral potential areas for Portugal was produced. It provides the starting point scenario needed for the implementation of a methodology aimed at the delineation of mineral safeguarding areas.
- A unificação dos inventários de geossítios como estratégia para a geoconservação em PortugalPublication . Aires, R.; Machado, Susana; Pereira, P.; Matos, João Xavier; Brilha, José BernardoSUMMARY: The unification of the two main geosites inventories developed in Portugal (University of Minho and LNEG) is important for the Portuguese geological community, for land use planning and nature conservation procedures. This task aims to reinforce the need of continuing the efforts for a geoconservation strategy in Portugal, stressing the need of the protection of the Portuguese geoheritage and its recognition within the official nature conservation institutions. In this work, the methodological setup of the inventories’ fusion is presented, with emphasis on the definition of information fields and the management of web databases.
- The state of the art of Phyllite-Quartzite Group Lower and Upper sequences, Mid-Late Devonian siliciclastic basinPublication . Matos, João Xavier; Pereira, Zélia; Mendes, Márcia; Albardeiro, Luís; Diez-Montes, Alejandro; Araújo, Vítor; Oliveira, José TomásRESUMO: O Grupo Filito-Quartzítico (GFQ) é considerado o substrato siliciclástico da Faixa Piritosa Ibérica (FPI), aflorando nas antiformas de Pomarão-Puebla de Guzmán, Valverde, Neves-Corvo– Rosário, Lousal–Caveira, São Francisco da Serra e Cercal. No setor norte da FPI o GFQ está presente em estruturas alóctones em São Domingos, Mértola, Alcaria Ruiva, São Barão, Roxo e Serrinha. A idade palinológica do GFQ, a cartografia geológica e a informação de sondagens de prospeção, permitem definir duas sequências principais: GFQ Inferior (base desconhecida e idade Givetiano a Frasniano, Biozonas de Miosporos AD Lem e BH) e GFQ Superior (idade Famenniano superior, Biozonas de Miosporos VCo, VH e LN). A sequência GFQ superior tem uma idade contemporânea da Sequência Inferior do Complexo Vulcano-Sedimentar da FPI e início da formação dos depósitos de sulfuretos maciços vulcanogénicos (p.e., jazigos Neves-Corvo, Lousal e Caveira de idade Estruniano).
- Caracterização preliminar da deformação dos ortognaisses alcalinos e hiperalcalinos da Faixa Blastomilonítica (Zona de Ossa-Morena)Publication . Roseiro, José; Moreira, Noel; Nogueira, Pedro; de Oliveira, Daniel Pipa SoaresSUMMARY: In the Blastomylonitic Belt (northernmost Ossa-Morena Zone), alkaline and peralkaline orthogneisses are found as elongated bodies with WNW-ESE to NW-SE orientation hosted within a strongly deformed Neoproterozoic to Lower Cambrian metasedimentary strata. Despite some similarities between them (ascribed to the very similar nature of their igneous protolith) the deformational features displayed in all of them are different, for example in the mineral segregation and recrystallization (including the development of augens) observed, and in different strike-dip orientation of foliations and lineation plunge. The dissimilarities are presumably due not only from different primary features, but also to the type of ductile shearing and metamorphic conditions they underwent. This way, field data will be complemented with petrographic studies for mineralogical and microdeformation characterization, and crossed to the regional structural information, thus constraining the deformation patterns of the alkaline-peralkaline orthogneisses on the Blastomylonitic Belt.