Repositório do LNEG
Repositório Científico do Laboratório Nacional de Energia e Geologia
Entradas recentes
Preliminary Ornamental Classification of Biotitic Granites from Cubal (SW of Angola)
Publication . Lisboa, Jose; Caessa, Paulo; Lopes, R.; Oliveira, Álvaro; Silva, Paulo Bravo; Fernández, J.; Rodrigues, José Feliciano; Manuel, José
ABSTRACT: In the Cubal region between Benguela and Huambo (SW of Angola), grey biotite granites of middle Paleoproterozoic age occur on a planation surface as residual reliefs, either of inselberg or inselgbirge type. The objective of this work is to carry out the preliminary classification of the grey granites of the Cubal region (SW of Angola), ranking the areas in relation to their potential in granites as ornamental rocks. Six granite lithotypes were identified, which can be grouped into 3 sets according to their textural characteristics. The petrographic analysis reveals that from a mineralogical point of view, granitic lithotypes are very similar with a significant content of plagioclase. The samples chemical analysis shows a homogeneous acidic composition in the granite composition range. Tests were carried out to determine real and apparent density, total and open porosity, water absorption at atmospheric pressure, compressive strength, and bending strength. The results show that the Cubal granites have the characteristics of quality ornamental stones, which in general can be used in all types of applications, in interior and exterior environments. Based on a set of variables, an empirical classification of the ornamental potential of the granites was made, where 4 levels of increasing potential in the study area are established.
Maps of Industrial Rocks and Minerals of Angola: CARMINA Project. Products obtained and main results
Publication . Fernández, J.; Lisboa, Jose; Iglesias-Martínez, Mario; Gumiel, J.C.; Feria, María Carmen; Francés, Alain Pascal; Merino-Martinez, Enrique; Manuel, José; Garcia-Lobon, Jose Luis
ABSTRACT: Recognizing the pivotal role of the sector in the socioeconomic development of the nation, the Government of the Republic of Angola has actively endorsed the establishment of a geological-mining cartography. This initiative, employing modern methodologies, is a fundamental tool for strategically planning mineral resource exploitation. The outcomes of this initiative underscore the remarkable diversity of substances and the considerable significance of the studied deposits. In the domain of Industrial Rocks and Minerals, specifically within the CARMINA subprogram, a comprehensive compilation of 30 geological-mining maps has been generated. These maps delineate Areas of Mining Potential, and are accompanied by corresponding reports that encapsulate the research findings and technical-analytical outcomes of the investigated regions. The undertaken efforts have unveiled the substantial potential for Natural Stone, featuring novel varieties of granites, marbles, and “exotic” rocks such as amazonites, sodalites, pegmatites, and carbonatites. The last refered rock types are particulary interesting since they serve as sources for industrial rocks and minerals, encompassing valuable resources like lithium and Rare Earths. Thus, these resources exhibit promising prospects in the context of the energy transition. Additionally, noteworthy deposits include high-purity quartz in Equimina region, feldspars in Giraúl area, kaolins and clays within the Cunene Anorthositic Complex. The systematic creation of mineral resource maps, along with the associated research, contributes to the provision of up-to-date information regarding the geological-mining potential of the studied territory.
The historical archive of LNEG slides collection of national scientific value - LAMINOTECA 1.0
Publication . Pereira, Zélia; Quental, Lídia; Jorge, Micael; Teixeira, Rui; Patinha, Pedro; Xavier Matos, João Manuel; Mesquita Soares, Sofia; Silva Mendes, Márcia Cristina; Pereira, Aurete; de Oliveira, Daniel Pipa Soares; Matos, Maria Luísa; Carvalho, Cristina Isabel Paulo; Dias, Ruben
ABSTRACT: The historical archive of the Laboratório Nacional de Energia e Geologia (LNEG) encompasses nearly 180 years of geological and mining activity, constituting an exceptional scientific repository and a national geological treasure. Among LNEG’s core missions is the preservation, processing, and dissemination of this unique heritage. The collection is recognised as part of the national scientific heritage, holding both historical and strategic importance for research and possessing considerable economic value. However, the existing collections must be properly organized and digitized to ensure their online accessibility through the LNEG GEOPORTAL platform. Achieving this goal requires the creation and development of a digital data centre that will facilitate and promote the consultation of the existing information. One of the archives in greatest need of urgent organization is the collection of rock thin sections and polished surfaces, which includes thousands of specimens preserved at LNEG. These materials are the result of decades of petrographic studies of rocks, fossils, and ores conducted across Portugal and its former overseas territories (now CPLP countries). The slides and polished surfaces are essential for rock characterisation, and their petrographic analysis provides invaluable support across multiple LNEG mission areas.
O arquivo histórico da coleção de lâminas do LNEG de valor científico nacional - LAMINOTECA 1.0
Publication . Pereira, Zélia; Quental, Lídia; Jorge, Micael; Teixeira, Rui; Patinha, Pedro; Xavier Matos, João Manuel; Mesquita Soares, Sofia; Silva Mendes, Márcia Cristina; Pereira, Aurete; de Oliveira, Daniel Pipa Soares; Matos, Maria Luísa; Carvalho, Cristina Isabel Paulo; Dias, Ruben
RESUMO: O arquivo histórico do Laboratório Nacional de Energia e Geologia (LNEG) constitui um acervo científico com quase 180 anos de atividade geológica e mineira, representando um banco de dados excecional e um repositório geológico nacional. Entre as áreas de missão do LNEG destaca-se a preservação, tratamento e disponibilização deste património único. Esta coleção é considerada património científico nacional, com relevância histórica e importância fundamental para a investigação estratégica do país, além de possuir elevado valor económico. Contudo, torna-se necessário que as coleções existentes sejam devidamente organizadas e disponibilizadas online através da plataforma GEOPORTAL do LNEG. Para alcançar este objetivo é, pois, necessário criar e desenvolver um centro de dados digital que facilite e promova a consulta da informação existente. Uma das coleções que requer organização urgente é a coleção de lâminas delgadas e superfícies polidas, composta por milhares de espécimes conservados no LNEG. Esta coleção resulta de inúmeros estudos petrográficos realizados ao longo de décadas sobre rochas, minérios e fósseis, abrangendo o território nacional e os antigos territórios ultramarinos (atualmente países da CPLP). As lâminas delgadas e superfícies polidas são fundamentais para a caracterização das rochas, constituindo um valioso suporte para diversas áreas da missão científica.
A New Geochemistry Exploration Method to Identify Deep VMS-Type Deposits - Application to the Cu-Zn Neves-Corvo Deposit, Iberian Pyrite Belt
Publication . Morais, Igor; Albardeiro, Luís; Rosado, Lúcia; Mirao, Jose; Xavier Matos, João Manuel; Batista, Maria Joao; Silva, Teresa; Barrulas, Pedro; de Oliveira, Daniel Pipa Soares
ABSTRACT: Mineral exploration in the Iberian Pyrite Belt follows increasingly deeper targets. The present study introduces an innovative methodology for the detection and identification of blind metallic mineral deposits, in particular volcanogenic massive sulfides based on surface rock coatings. This approach follows the identification pathways of upward metal escape routes and metal distribution in rock fractures located in different anisotropic or isotropic planes above the Neves-Corvo VMS deposit ore lenses, using VP-SEM-EDS and XRD. Coatings are dominated by poorly crystalline to amorphous phases, with goethite and birnessite as the main Fe- and Mn-bearing minerals. Copper, zinc and lead are systematically enriched in coatings developed above or near the ore bodies, reflecting chalcopyrite, sphalerite and galena acidic leaching. Tin shows a restricted and heterogeneous distribution, while Ni and Co display no systematic relationship with the ore bodies. Barium and late Ba-Pb-(Zn) mineralization along fault zones record VMS mineralization. Lead isotopic coating signatures overlap those of IPB massive sulfide deposits, confirming a dominant VMS-derived contribution. Fe-Mn coatings were formed by precipitation from ascending meteoric fluids that leached metals from massive sulfides, their alteration halos, and surrounding lithologies, preserving the geochemical footprint of buried mineralization. This approach constitutes a new patented exploration tool.