Repositório do LNEG

3D predictive modelling using Artificial Neural Network Analysis in the Neves-Corvo deposits [Resumo]

Publication . Batista, Maria Joao; Represas, Patricia; Carvalho, João; Araújo, Vítor; Marques, Fábio; Xavier Matos, João Manuel; Morais, Igor; Albardeiro, Luís; Inverno, Carlos; de Oliveira, Daniel Pipa Soares; Dias, P.

ABSTRACT: This study focuses on mineral and lithological vectoring to target new VMS deposits in the Neves-Corvo district, Portugal. Neves-Corvo is a world-class deposit in the Iberian Pyrite Belt, discovered in 1977 by ground gravity survey and one of Europe’s important copper-zinc producers. The deposit is hosted in volcano-sedimentary sequences within a moderately folded and thrust-faulted setting. Previous studies show differences between massive sulphide ores and stockwork ores, especially in trace-element associations. These geochemical particularities, combined with decades of exploration data, make the area well suited for advanced statistical and multivariate analysis. This study will apply an Artificial Neural Network Analysis (ANNA) methodology to the geochemical data, interpolated from boreholes, and a 3D rock density model, obtained by a constrained inversion of gravity data, to identify patterns that other methods might overlook, thereby improving targeting for new VMS mineralization. ANNA can extract trends from complex datasets and perform non-parametric analysis that do not assume a-priori relationships between variables. Therefore, instead of relying on linear or quadratic regressions approaches, this study employs the so-called black box to determine a mathematical function that can adequately approximate the representation of dependent and independent variables. In this study, the number of variables is considerably smaller than the number of training cases available. The training progresses iteratively, using the previous outputs to carefully and progressively adjust the predictors in an iterative manner, allowing for a continuous validation (based in a set of data taken from the total data before training to monitor the performance of the training in each cycle or iteration) of the different scenarios. The geological model was produced, and the drill-hole density database was used to constrain the 3D gravity inversion. All information was laid in a 5mx5mx5m 3D mesh, eliminating the blocks with missing data. The formatted data was then inputted into in STATISTICA’s ANNA software. The variables considered for the first step of ANNA were Cu, Zn, rock density, gravity inversion and Cu/Zn ratio for the Lombador, Neves Graça, Corvo and Zambujal deposits. From the training and validation procedures, it was possible to conclude that using gravity inversion as target and Cu/Zn and rock density as input data produced the more accurate prediction map.

Using ESA NoR high-resolution data to support coastal management: the Baleal– Óbidos lagoon case study [Resumo]

Publication . Nave, Silvia; Gonçalves, Pedro; Albardeiro, Luís; Mesquita Soares, Sofia

ABSTRACT: The study of coastal cliffs is essential for territorial management, public safety, and environmental preservation, given their inherently dynamic and geomechanically unstable nature. The significant rise in coastal area occupation requires the development of strategically focused methodologies that facilitate efficient and rapid monitoring of coastlines featuring sea cliffs, where mass movements are more likely to occur. Monitoring these landforms requires decimetre-scale spatial resolution to capture geomorphological changes such as clifftop retreat, block detachment, and the development of structural discontinuities. This study examines a small section from a cliffed coastline bordered by a continuous sandy beach located on the western coast of Portugal, between Baleal and the Óbidos Lagoon, a gently curved stretch of coast with approximately northeast to southwest orientation. The sea cliffs, reaching up to 50 meters above sea level, with varying slopes and heights, are broken up by two fluvial valleys, forming a local beach-dune system in those areas. The multi-sensor analysis carried out in this analysis enabled the precise identification of clifftop retreat and structurally significant discontinuities along the Praia d'El Rey sector. Multi- temporal differencing of Vexcel Elevate DTMs (2020–2024) revealed spatially coherent zones of material loss along the cliff face and beach interface (Figure 1). However, these results remain preliminary: uncertainty persists due to (i) tidal stage differences between acquisitions affecting intertidal elevations, (ii) co-registration offsets between epochs, and (iii) unvalidated vertical accuracy of the DTM products at this site. This study highlights the critical role of initiatives like the ESA Network of Resources, supported by the European Union Space Programme, in advancing efficient and timely monitoring of sea- cliff morphology. By reducing barriers to the use of commercial ultra-high-resolution satellite data, these programmes enable high-precision coastal research. In the absence of such institutional support, sub-metre imagery would remain largely inaccessible to public research institutions, underscoring the strategic significance of European Earth Observation programmes in supporting evidence-based coastal hazard management.

Geochemistry of historical smelting slags from S. Domingos (Iberian Pyrite Belt) and implications for metal recovery [Resumo]

Publication . Silva, Teresa; Morais, Igor; Albardeiro, Luís; Solá, A. Rita; de Oliveira, Daniel Pipa Soares

ABSTRACT: The historical mining area of S. Domingos, located in the Iberian Pyrite Belt (IPB), southwestern Portugal, hosts significant accumulations of mining wastes including, smelting slags, iron oxides, milled blocks of pyrite and other residues resulting from centuries of processing Cu-rich massive sulfide ores. Polymetallic sulfide exploitation in this region dates to pre-Roman times and continued until 1966. These slags represent an important record of historical metallurgical practices and a potential secondary resource for critical and strategic raw materials (CRM/SRM) and other valuable metals. This study investigates the geochemical composition and mineralogical characteristics of historical smelting slags, to access not only their potential to metal recovery, but also their associated environmental risks. The slags are heterogeneous and chemically unstable waste products, typically Fe-rich, and dominated by fayalite, Fe2+2SiO4 (the iron-rich member of the olivine mineral group) together with glassy matrices. Fayalite is the result of the reaction of iron oxide with silica at high temperatures and host a range of metals including As, Ba, Co, Cu, Sn, Pb, Sr and Zn. Weathering processes promote metal mobilization of these elements, contributing to local contamination and to the development of acid mine drainage (AMD) products in the surrounding areas. Geochemical assessment indicates that significant quantities of valuable metals remain trapped within these historical slags due to inefficient recovery during earlier smelting technologies. Studies across the IPB suggest that mining wastes may contain significant valuable reserves of metals such as Fe, Zn, Cu and Pb, as well as CRM and other important trace metals. Consequently, these residues represent potentially promising targets for reprocessing using advanced metallurgical or hydrometallurgical technologies. Detailed geochemical characterization provides insights supporting the development of sustainable recovery strategies within a circular economy framework for historic mining districts of the Iberian Pyrite Belt. The results underscore the dual importance of recovering the S. Domingos slags as potential secondary mineral resources, while also mitigating the environmental impact associated with AMD.

Mapping critical raw materials in Portugal [Resumo]

Publication . de Oliveira, Daniel Pipa Soares; Gonçalves, Pedro; Filipe, Augusto; Santos, Sara; Albardeiro, Luís; Morais, Igor; Xavier Matos, João Manuel; Salgueiro, Rute

ABSTRACT: Reliable and secure access to Critical and Strategic Raw Materials (CRM/SRM) is a strategic requirement for the European Union, underpinning industrial competitiveness, technological innovation, and the transition toward a climate-neutral economy. In response to increasing supply risks, high import dependency, and growing demand driven by renewable energy systems and e-mobility, this work presents the second Critical Raw Materials Deposits Map of mainland Portugal, compiled at a scale of 1:700000. The map integrates geological, spatial, and mineral resource data derived primarily from the SIORMINP database (Information System of Portuguese Occurrences and Mineral Resources), developed and maintained by LNEG. This database currently contains over 2453 documented mineral occurrences, including 1214 strategic and critical mineral occurrences associated with EU-defined critical raw materials, which were systematically identified and evaluated. Key commodities represented include tungsten, lithium, antimony, titanium, rare earth elements, cobalt, tantalum-niobium, feldspar, nickel, and copper, among others. The systematic integration of these datasets provides a robust framework for national and European-scale mineral intelligence. A comprehensive scientific and cartographic methodology was applied, combining official geological mapping, the tectonostratigraphic domains of the Iberian Massif, and shaded-relief terrain visualization. The mineral occurrences were classified according to deposit type, size, structural orientation, and mineralization source, allowing visualization of both spatial distribution and metallogenic context. Cartographic design followed established visual variables theory to convey multidimensional geological information while maintaining clarity at the chosen scale. The resulting map represents a significant advance in national mineral intelligence, supporting mineral exploration targeting, resource assessment, land-use planning, and evidence-based policy decision-making. It also contributes to pan-European datasets, promoting data harmonization and international comparability. Conceived as a dynamic product, the map is designed to be periodically updated in line with revisions to the EU Critical Raw Materials list. Overall, this work demonstrates the value of integrated geological and cartographic approaches in strengthening raw material supply knowledge at both national and European scales.