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- Changing Social Perceptions on Mining-Related Activities: A Key Challenge in the 4th Industrial RevolutionPublication . A., MateusWe are living in a period of multiple and accelerating changes where new uncertainties emerge constantly. Guidelines for economic growth are changing, social demands and environmental concerns are growing, and technological advancements are succeeding at rates never seen before. The main drivers of these changes are mostly related to digitization, decarbonization and dematerialization processes of economies, which follow the recent improvements achieved in biotechnology, digital networks, software design, and information and communication technologies. The ongoing technological (r)evolution includes continued linear progressions of solutions of widespread use along with innovations of exponential increase that will significantly shape the future and have potential to influence the current social and cultural patterns. However, all these transformations stimulate the reliance on a large number of minerals and metals whose increasing demand cannot be fulfilled on the basis of reuse, recycling and/or substitution practices. In other words: the full development of digital, eco-efficient and low-C intensity economies with higher levels of automation will require considerable inputs of raw materials derived from primary resources to balance the demand/supply ratio, filling the gaps of material stocks and flows in the economy that are not provided by secondary sources, even when suitably managed. So, mineral exploration and mining will remain fundamental in the completion of pathways to the future, as occurred throughout the history of human civilization. Notwithstanding this evidence, clearly demonstrated in many studies, the access to mineral resources are becoming increasingly difficult worldwide and mining-related activities are even more perceived negatively by society.
- Current and Foreseen Tungsten Production in Portugal, and the Need of Safeguarding the Access to Relevant Known ResourcesPublication . A., Mateus; Lopes, Catarina; Martins, Luís; GonçalvesThe economic and strategic importance of tungsten is widely recognized, but several concerns exist on its stable future supply. Portugal is one of the main tungsten producers in Europe, having generated ≈121 kt of contained tungsten in mineral concentrates from 1910 to 2020, i.e., ≈3.3% of the global production documented for the same time period. Since the early nineties, tungsten mining in Portugal is confined to the Panasqueira deposit which accounts for 79% of the country reserves (≈5.4 kt). However, according to the performed Generalized Verhulst and Richards curve-fitting forecasts, there is a significant future potential for increasing production in Portugal due to the low (<2%) depletion rates of the remaining known tungsten resources (≈141 kt). This projected growth is not necessarily guaranteed, depending on many unpredictable economic, technological, and political factors, besides appropriate social consents. Even so, a prudent land-use planning oriented to long-term needs should avoid the sterilization of the most relevant tungsten resources so far identified in the country. These are resources of “public importance”, as objectively demonstrated with a weighed multi-dimensional (geological, economic, environmental, and social) approach. Safeguarding the access to these resources does not implicate more than ≈6% of the Portugal mainland territory. The joint interpretation of results independently gathered for tungsten production forecasts and for the definition of areas hosting tungsten resources of public importance, provides additional support to political decisions on the urgent need to reconcile mineral exploration surveys and mining with other land uses.
- Challenges and opportunities for a successful mining industry in the futurePublication . A., Mateus; Martins, LuísModern models of sustainable economic growth are metal-intensive and will not be successful in the future unless a continuous supply of mineral-derived products is ensured. Despite this being logical, there is still a significant reluctance regarding mineral exploration and mining activities, often reflected in: (i) unfavourable public opinions; and (ii) absence of political measures or continuity of agendas that actually appreciate the way minerals are produced and the players directly or indirectly involved in this production. To succeed, the mining industry will have to (re)define its strategy and find innovative approaches to old problems and clearly demonstrate that mineral products can be efficiently delivered to support global development and assist suitable paths to welfare and quality of life, thus also providing real value to all concerned. In this study we give a concise review of the main challenges posed to the mining industry, and also indicate the most relevant opportunities and advance some proposals to constructively face the identified weaknesses and threats. The fundamental outcome is that the long-term balance between supply and demand of mineral products requires concerted actions on different fronts aiming: (i) the safeguarding of known resources; (ii) high-quality (scientifically and technologically driven) exploration surveys; (iii) improvements in mining and mineral transformation/ beneficiation; (iv) advances in consistent combinations of primary and secondary sources of raw materials, along with higher concerns on their judicious use; (v) effective and stable mining policies; and (vi) new insights on the role played by the mining industry through fruitful dialogues with society in general.
- 57Fe Mossbauer spectroscopy study of the correlation between the Fe3+ content and the magnetic properties of natural Cr-spinelsPublication . Waerenborgh, João C.; Figueiras, Jorge; A., Mateus; A. Gonçalves, MárioBoth the Fe oxidation degree and the magnetic properties determined by 57Fe Mössbauer spectroscopy were used to characterize the Cr-spinels from the Beja-Acebuches Ophiolite Complex (SE Portugal). Two different types of Cr-spinel were observed. The first one has an average Fe3+/(Fe total) ≈ 25%, and corresponds to unaltered Cr-spinel grains which remain paramagnetic down to 6K. The second one results from the alteration of the first type, has an average Fe3+/(Fe total) ≈40% and order magnetically between 222 K and 78 K. Fe3+/(total Fe) increases with the magnetic ordering temperature. The grain population ordering at the highest temperatures, in the range 202–222K, has the highest Fe3+/(total Fe) ≈ 58%. Quantitative Fe site distributions can be obtained from room-temperature Mössbauer data if the different recoilless factors for tetrahedral Fe2+ and octahedral Fe3+ are considered. The observed second-order Doppler shifts are consistent with Mössbauer temperatures of 330K and 605K, reported in the literature for tetrahedral Fe2+ and octahedral Fe3+ in other oxide spinels. The differences in the magnetic ordering temperatures allowed the characterization of both types of Cr-spinels using a single Mössbauer absorber, thus avoiding the need to separate them physically, which, in this case, would be very difficult. The results are compared to those obtained for other Cr-spinels and, for the first time in the case of natural Cr-spinels, the increase of their magnetic ordering temperatures with their oxidation degree, resulting from natural processes, is discussed in terms of the magnetic exchange interactions between the Fe cations.
- Interplate versus intraplate strike-slip deformed belts: examples from SW IberiaPublication . Romão, J.; Ribeiro, Antonio; Pereira, E.; Rodrigues, J.; A., Mateus; Noronha, F.; Dias, R.A complete transition in tectonic style between pure thrust belts and pure strike-slip beltscan be envisaged, both in interplate and intraplate settings, by a combination of thrust and strike-slipcomponents of displacement. The accommodation of shortening components in strike-slip deforma-tion belts has been discussed recently on the basis of two alternative perspectives: (1) the “sub-horizon-tal attachment model”, where discrete strike-slip faulting of rigid blocks in the schiszosphere evolves tocontinuous movement in plastosphere through a bottom-up driving mechanism controlled by verticalcoupling across the lithosphere, and (2) the “accommodation model” that considers decoupling with-in a heterogeneous and anisotropic plastosphere. Two examples of variable shortening componentaccommodation in strike-slip deformation belts of the SW Iberia Variscides are reported and discussed.In the Tomar-Badajoz-Córdoba shear zone, an important shortening component is accommodated inflat-lying bends around the horizontal axis within a WNW-ESE flower-structure with sinistral strike-slip component; the geodynamic evolution points to an intraplate setting for this structure. In the N-S, Porto-Tomar-Ferreira do Alentejo, dextral shear zone, the shortening component is restricted torestraining bends around the vertical axis; the geodynamic evolution allows inferring a transformnature for this structure, thus indicating an interplate setting. For these examples, the “accommodationmodel” is preferred to the “sub-horizontal attachment model”
- Geodynamic evolution of the South Variscan Iberian Suture as recorded by mineral transformationsPublication . Figueiras, Jorge; A., Mateus; A. Gonçalves, Mário; Waerenborgh, João; Fonseca, PauloNew structural, petrographic, mineralogical and geochemical data from the Beja-Acebuches Ophiolite Complex (BAOC) are presented, and reviewed together with data published elsewhere. The new data obtained shed light on questions such as: 1) the relative importance of the obduction event; 2) its geological record in the deep levels of BAOC; 3) the nature and intensity of the Variscan metamorphism and deformation during subsequent continental (arc) collision; 4) the age relationships between BAOC and the Beja Igneous Complex; and 5) by means of numerical modelling, the thermal metamorphism of the Ossa-Morena autochthonous terranes induced by the ophiolite obduction. The emerging picture is that of a fairly simple overall geological evolution for BAOC, seamlessly integrated within the evolution of the southern branch of the Iberian Variscides. Obduction of BAOC is a relatively minor early event in the general NE–SW convergence that gave rise to the orogen as seen regionally and is recorded by an anisotropic, high-temperature, metamorphic fabric at the gabbro levels and by subtle features of the chemical composition of primary minerals at the underlying peridotite level; it caused chilling of the obducted ophiolitic slab and no significant metamorphism on the autochtonous rocks of the Ossa-Morena Zone. BAOC underwent most of its deformation and (amphibolite facies) metamorphism during a later collisional event, that took place as the most primitive rocks of the Beja Igneous complex were being intruded, and whose waning stages are responsible for extensive serpentinisation of peridotites and for important aquocarbonic fluid discharges along the semibrittle–brittle shear zones meanwhile developed.
- Strain partitioning in transpressive shears zones in the southern branch of the Variscan Ibero-Armorican arcPublication . Dias, R; A., Mateus; Ribeiro, AntonioThe Torre de Moncorvo region (NE Portugal) is a key-sector of the Autochthon Domain of the Iberian Terrane. The region experienced Variscan deformation in the southern branch of the Ibero-Armorican Arc wherein the early structures (of Upper Devonian age—D1) denotes the establishment of a heterogeneous sinistral transpressive regime. This regime was also responsible for the development of large-scale left-lateral shear zones whose direction is subparallel to major folds. Finite strains analyses were carried out in the Torre de Moncorvo region using the normalised Fry method on different strain markers: (1) distribution of detrital quartz grains in quartzite rocks of Arenigian–Lanvirnian age; (2) arrangement of oolites in discontinuous Ordovician–Silurian ironstone horizons; (3) the rotation experienced by Skolithos preserved in Lower Ordovician metasedimentary clastic rocks. The results obtained indicate the predominance of slightly prolate strain ellipsoids. Nevertheless, the variation of their orientation around mesoscopic folds emphasises the role of strain partitioning in a transpressive regime, suggesting that different folding mechanisms were active in the course of the same deformation phase. For the studied cases, tangential longitudinal strain and flexural shear combined with regional sinistral shear seem to be the most common mechanisms of folding. Some of these three-dimensional theoretical models for strain patterns in folds could be used in other regions, where a transpressive regime is inferred.
- Recursos naturais de lítioPublication . A., MateusA necessidade de opções suficientes para armazenamento de energia advém da evolução recente do setor eletroprodutor e tendência veloz para a eletrificação do setor automóvel. A solução tecnológica que hoje se afirma como a mais vantajosa envolve baterias recarregáveis de iões de lítio (LIB) com diferentes configurações, acopláveis em sistemas estacionários de armazenamento de energia e veículos elétricos. Esta solução deverá prevalecer até 2050, competindo com outras alternativas ainda longe de massificação. O fabrico em larga escala de LIB altera drasticamente o padrão de repartição do consumo de lítio nos mercados que abastecem diferentes setores industriais, exercendo forte pressão junto do limitado número de centros de mineração e transformação da matéria- -prima natural no sentido de aumentarem rapidamente o seu ritmo de produção. Esta pressão tenderá a aumentar nos próximos anos a menos que, entretanto, seja possível incrementar de forma satisfatória as taxas de reciclagem das LIB e do lítio; atualmente, os valores das primeiras são insignificantes e menos de 1% do Li consumido é reciclado. As reservas globais conhecidas totalizam ≈15 Mt e estimativas conservadoras posicionam os recursos disponíveis em torno de 53 Mt, embora possam ascender a 62 Mt se boa parte dos recursos inferidos for confirmada. Mantendo-se as taxas de esgotamento anual dos recursos remanescentes registadas nos últimos 5 anos, os picos de exploração serão atingidos a breve trecho, comprometendo muitas das linhas de desenvolvimento tecnológico imaginadas para o futuro, em particular as que se relacionam com a mobilidade eléctrica. Deste modo, a “corrida ao lítio” tem vindo a ganhar expressão crescente, sustentando investimentos significativos em prospecção e pesquisa mineral para melhor caracterizar os recursos existentes e aumentar as reservas globais. Esta é também a razão que explica o recrudescimento dos trabalhos de prospecção em Portugal, um dos grandes produtores de concentrados minerais litiníferos, ocupando desde há muitos anos a 6ª ou 7ª posição do ranking mundial com uma produção média anual de 15800 toneladas entre 1980 e 2016, mas cujo potencial se encontra por avaliar em detalhe.
- Main characteristics and genesis of the Vale de Pães skarn (Cuba-Vidigueira, Ossa Morena Zone, Portugal)Publication . Salgueiro, R.; Inverno, C.; A., MateusThe Vale de Pães (Cuba-Vidigueira) mineralisation is composed of magnetite ± sulphides and hosted in a Pre-Variscan metamorphic sequence intruded by igneous rocks belonging to the Beja Igneous Complex. Its mineral and chemical features are compatible with a zoned Fe-skarn: Mg-rich (Fo + Di90, oxidised) and Ca-rich (Grs + Di81-39, oxidised or relatively reduced). In the Fe-Mg skarn, magnetite deposition occurred along with the anhydrous mineral assemblage at ≈ 600 °C; sulphides precipitated from the retrograde stage onset (≤ 550 °C) and during the hydrated and carbonate phases formation period (< 420 °C). In the Fe-Ca skarn, magnetite precipitated during the retrograde stage (< 550 °C) together with the hydrated mineral association, and was followed by sulphides at ≈ 400°C. The mineralising process involved moderate-high salinity fluids and was controlled by variations in redox potential and pH.
- Pb-Nd-Sr Isotope Geochemistry of Metapelites from the Iberian Pyrite Belt and Its Relevance to Provenance Analysis and Mineral Exploration SurveysPublication . Luz, Filipa; A., Mateus; Ferreira, Ezequiel; Tassinari, Colombo G.; Figueiras, JorgeThe Iberian Pyrite Belt is a world-class metallogenic district developed at the Devonian-Carboniferous boundary in the Iberian Variscides that currently has seven active mines: Neves Corvo (Cu-Zn-Sn) and Aljustrel (Cu-Zn) in Portugal, and Riotinto (Cu), Las Cruces (Cu), Aguas Teñidas (Cu-Zn-Pb), Sotiel-Coronada (Cu-Zn-Pb), and La Magdalena (Cu-Zn-Pb) in Spain. The Iberian Pyrite Belt massive sulfide ores are usually hosted in the lower sections of the volcano-sedimentary complex (late Famennian to late Visean), but they also occur in the uppermost levels of the phyllite-quartzite group at the Neves Corvo deposit, stratigraphically below the volcano-sedimentary complex. A Pb-Nd-Sr isotope dataset was obtained for 98 Iberian Pyrite Belt metapelite samples (from Givetian to upper Visean), representing several phyllite-quartzite group and volcano-sedimentary complex sections that include the footwall and hanging-wall domains of ore horizons at the Neves Corvo, Aljustrel, and Lousal mines. The combination of whole-rock Nd and Sr isotopes with Th/Sc ratios shows that the siliciclastic components of Iberian Pyrite Belt metapelites are derived from older quartz-feldspathic basement rocks (–11 ≤ εNdinitial ≤ –8 and (87Sr/86Sr)i up to 0.727). The younger volcano-sedimentary complex metapelites (upper Tournaisian) often comprise volcanic-derived constituents with a juvenile isotopic signature, shifting the εNdi up to +0.2. The Pb isotope data confirm that the phyllite-quartzite group and volcano-sedimentary complex successions are crustal reservoirs for metals found in the deposits. In Neves Corvo, where there is more significant Sn- and Cu-rich mineralization, the higher (206Pb/204Pb)i and (207Pb/204Pb)i values displayed by phyllite-quartzite group and lower volcano-sedimentary complex metapelites (up to 15.66 and 18.33, respectively) suggest additional contributions to the metal budget from a deeper and more radiogenic source. The proximity to Iberian Pyrite Belt massive sulfide ore systems hosted in metapelite successions is observed when (207Pb/204Pb)i >15.60 and Fe2O3/TiO2 or (Cu+Zn+Pb)/Sc >10. These are important criteria that should be considered in geochemical exploration surveys designed for the Iberian Pyrite Belt.