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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.
- 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.
- Geophysical surveys in the Portuguese sector of the Iberian Pyrite Belt: a global overview focused on the massive sulphide exploration and geologic interpretationPublication . Matos, João Xavier; Carvalho, João; Represas, Patricia; Batista, Maria Joao; Sousa, P.; Ramalho, Elsa; Marques, Fábio; Morais, Igor; Albardeiro, Luís; Gonçalves, Pedro; Dias, P.ABSTRACT: The application of geophysical techniques to massive sulphide deposits exploration has proven to be a success in the Iberian Pyrite Belt (IPB) metallogenetic province, both in Portugal and in Spain. Several hidden deposits were discovered through the interpretation of geological models, supported by geophysical data collected in land and airborne surveys, as well as applied using down hole techniques in selected drill holes. This paper presents an overview of the methodologies applied in Portugal in the South Portuguese Zone (SPZ) geological domain, where the IPB is included, mostly by the LNEG and mining companies, with emphasis on the interpretation of the regional gravity, magnetometry and radiometry surveys, published in 1/400 000 scale by the EXPLORA/Alentejo2020 Project. In this regional mapping program, the large volume of data collected by LNEG and mining companies since the 1960’s was compiled and processed. The integrated interpretation and correlation between these methods will enable a better planning of new IPB exploration investments. IPB Volcano-Sedimentary Complex (VSC, Famennian to Late Visean age) lineaments are well defined in the gravity and magnetic fields along the IPB western region (e.g. Alcoutim/Neves-Corvo/Montinho/Sesmarias/Lousal/Caveira). Aeromagnetic data also reflect deep and large anomalies related with the SPZ basement. A rock density database is presented and used to interpret the gravity data. Radiometric map (Natural Radioactivity), based mostly in airborne radiometric surveys, show contrasts between rocks in Paleozoic, Mesozoic and Cenozoic formations and correlations with geological and hydrothermal mapping are highlighted. The use of geophysical techniques is particularly critical in areas where VSC is concealed by younger sediments (e.g. Baixo Alentejo Flysch Group and/or Cenozoic formations), allowing the selection of target areas. Case studies are discussed based on electromagnetic, seismic and magnetotelluric methods and on the high mineral potential of defined targets. Multilayered data correlation (geophysics including petrophysical data, geochemistry and stratigraphic high-resolution models) is a key prospecting methodology and is essential for the accurate modelling of ore horizons and geological structures. Considering the IPB potential for VMS deposits, including the possible discovery of new giant (> 200 Mt) deposits, an increase of investment in new geophysical methods can be predicted. LNEG development of R&D projects such as EXPLORA/Alentejo2020 and SmartExplorationTM/H2020 also contribute to a favourable setting in the province, both in near mining and green fields scenarios. Thus, new discoveries are expected, like others made in the recent times in the IPB Portuguese sector, such as Lagoa Salgada (SFM, 1992, SFM; Redcorp/EDM, 2011; Redcorp/Ascendant/EDM, 2017), Semblana (Somincor-AGC-Lundin Mining, 2010), Monte Branco (Somincor-Lundin Mining, 2012) and Sesmarias (Maepa/Avrupa, 2014). The importance of these data goes beyond the mineral exploration purpose. Since some of them use rock and mineral physical properties that can be related with environmental contamination (e.g. radiometry and magnetics) they can also be used in geochemical background studies, acid mine drainage and metal dispersion. Therefore, they can also promote a deeper knowledge in other areas of research related with environment preservation.
- Geochemistry of Iberian Pyrite Belt Portuguese sector massive sulfide deposits-related volcanic rocks. Considerations on hydrothermal alteration, petrology and tectonic evolutionPublication . Morais, Igor; Albardeiro, Luís; Batista, Maria Joao; Matos, João Xavier; Solá, A. Rita; de Oliveira, Daniel Pipa Soares; Salgueiro, Rute; Araújo, Vítor; Pacheco, NelsonABSTRACT: A geochemical compilation database of the main volcanic units of the Volcano-Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB), one of the largest provinces of massive sulfides on a global scale, is presented and discussed. For this purpose, we used several mineral exploration rock geochemistry databases from six IPB areas, namely Cercal, Lagoa Salgada, Lousal, Aljustrel, Neves-Corvo and Chança, regarding unaltered/hydrothermaly altered felsic volcanic units interbedded in the Famennian-Late Visean volcano-sedimentary sequences of the VSC. Volcanic rocks within the Phyllite-Quartzite Formation (Givetian-Famennian) IPB basement were also considered. From this, Neves-Corvo sector rhyolites (Rhyolite type 1 and 2) present the most intense hydrothermal alteration, directly related with the age of mineralization and coeval with hosted VSC sedimentary formations. Similar cases were also observed in the volcanic units hosting Lagoa Salgada, Chança and Aljustrel Volcanic-hosted massive sulfide (VHMS) deposits. The variety of felsic and intermediate volcanic rocks in the IPB (and within each sector) reflect different petrogenetic processes and/or distinct crustal sources. Application of Zr vs TiO2 binary diagrams allows to define three main trends of andesitic (Lagoa Salgada and Chança sectors), dacitic-rhyodacitic (Aljustrel sector) and rhyolitic (Cercal, Neves-Corvo, Aljustrel and Lousal sectors) composition. Cercal rhyolites are the most evolved felsic rocks (Zr/TiO2 ≈ 1562), followed by Neves-Corvo rhyolites (Zr/TiO2 ≈ 936), Lousal (Zr/TiO2 ≈ 845) and Aljustrel (Zr/TiO2 ≈ 840). In addition, four distinct compositional clusters can be distinguished based on Al2O3/TiO2 vs Zr/TiO2 and Al2O3/Zr vs TiO2/Zr ratios according to its nature as, rhyolitic, rhyodacitic/dacitic and andesitic, probably reflecting differential partial melting rates. Ybn vs La/Yb(n) diagram ratio indicates that Neves-Corvo (mainly 2 types of rhyolites), Aljustrel (Tufo da Mina rhyolitic unit), as well as Lagoa Salgada sector rhyolites are projected along FIIIa and FIIIb rhyolite fields considered of higher metalliferous potential in the IPB, once their petrogenetic processes are considered ideal to trigger, sustain and host hydrothermal systems and consequently VHMS deposits. Future work, combining geochemical characterization of each volcanic unit with their stratigraphic positioning, is essential in order to achieve a correct correlation between the different sectors and, is therefore, a useful tool in IPB mineral exploration and drill-hole data correlation.
- Modelling of the Neves Corvo AreaPublication . Inverno, Carlos; Rosa, C.; Matos, João Xavier; Carvalho, João; Castelo-Branco, José Mário; Batista, Maria Joao; Granado, Isabel; Oliveira, José Tomás; Araújo, Vítor; Pereira, Zélia; Represas, Patricia; Solá, A. Rita; Sousa, Pedro
- Um novo método de prospeção geoquímica para a identificação de depósitos profundos do tipo VMS. Aplicação ao depósito de Cu-Zn de Neves-Corvo, Faixa Piritosa IbéricaPublication . Morais, Igor; Rosado, L.; Albardeiro, Luís; Mirao, Jose; Batista, Maria Joao; Matos, João XavierSUMMARY: The fast energetic transition in the world needs large amounts of mineral resources that are currently scarce. For the suppression of these needs, new mineral deposits must be found, demanding the development of new exploration techniques. Currently, in several metalogenetic provinces, surface deposits are rare. In the Iberian Pyrite Belt, geophysical techniques, namely gravimetry and electromagnetics, have been used over the last years leading to the discovery of several hiden Volcanogenic Massive Sulphide deposits (VMS). Therefore, it is proposed a new geochemical technique that, through the chemical analysis of rock coatings, can lead to the identification of mineral deposits located at greath depth. The method is represented by the European Patent EXPLORA – LNEG/Évora University-Hércules Laboratory.
- Geochemical exploration and assessment of environmental impacts in the Portuguese sector of the Iberian Pyrite BeltPublication . Batista, Maria Joao; Mateus, A; Matos, João Xavier; Gonçalves, Mário A.; Figueiras, Jorge; Abreu, Maria Manuela; Luz, FilipaABSTRACT: This work intends to briefly report the history and application of geochemical exploration techniques in the Iberian Pyrite Belt (IPB). The use of geochemistry in IPB for exploration purposes started in 1950s. Together with geophysics, the soil geochemical exploration surveys performed over several decades were responsible for important discoveries such as Carrasco and Feitais ore-bodies. However, the continuous development of analytical methods and the progress in data processing/modelling led to significant changes in the planning of sampling surveys, and their specific objectives, as well as in the accuracy of geochemical anomalies definition and corresponding interpretation. As a consequence, the number of samples involved in each survey was significantly reduced, but the chemical elements analysed with improved detection limits were considerably extended; additionally, geochemical anomalies were better resolved. Notwithstanding this evolution, data obtained in early soil geochemical surveys (notably by the Serviço de Fomento Mineiro) are still useful in the development of preliminary approaches at a regional scale. Over the years, many studies were made for exploration and environmental assessments, the most relevant of them reported in this chapter. Natural distributions of chemical elements were also identified in these studies as background (if pristine conditions are present) or baseline (depending how disturbed is the area covered by the sampling survey) values. Large part of IPB was, and still is, subjected to poly-metallic mineral exploration or mining, being also the focus of environmental evaluation and/or remediation projects on particular areas that, being the target of long-lasting human intervention, represent paradigmatic case-study examples. The exploration and exploitation works carried out by national and foreign private companies were, and still are, very important for innovative achievements in IPB along with copious contributions from the Portuguese R&D public institutions. Presently, LNEG possesses a vast quantity of geochemical data that can be provided for companies that wish to start their activity in the IPB; some of these datasets are compiled to a unique integrative map also presented in this work. Stream-sediments geochemistry, hydrogeochemistry and lithogeochemistry (of outcropping rock and drill-core samples) represent also important sources of geochemical data in regional or detailed studies over specific target areas in the IPB. However, these techniques are beyond the scope of the present paper which aimed at providing a general overview of the importance of soil geochemistry studies in the current knowledge of the IPB.
- Introduction and geological setting of the Iberian Pyrite BeltPublication . Inverno, Carlos; Díez-Montes, Alejandro; Rosa, C.; García-Crespo, J.; Matos, João Xavier; García-Lobón, J. L.; Carvalho, João; Bellido Mulas, Félix; Castelo-Branco, José Mário; Ayala, C.; Batista, Maria Joao; Rubio, F.; Granado, Isabel; Tornos, F.; Oliveira, José Tomás; Rey, C.; Araújo, Vítor; Sánchez-García, Teresa; Pereira, Zélia; Represas, Patricia; Solá, A. Rita; Sousa, Pedro
- Geochemical exploration and assessment of environmental impacts in the Portuguese sector of the Iberian Pyrite BeltPublication . Batista, Maria Joao; Mateus, António; Matos, João Xavier; Gonçalves, M. A.; Figueiras, Jorge; Abreu, Maria Manuela; Luz, FilipaABSTRACT: This work intends to briefly report the history and application of geochemical exploration techniques in the Iberian Pyrite Belt (IPB). The use of geochemistry in IPB for exploration purposes started in 1950’s. Together with geophysics, the soil geochemical exploration surveys performed over several decades were responsible for important discoveries such as Carrasco and Feitais ore-bodies. However, the continuous development of analytical methods and the progress in data processing/modelling led to significant changes in the planning of sampling surveys, and their specific objectives, as well as in the accuracy of geochemical anomalies definition and corresponding interpretation. As a consequence, the number of samples involved in each survey was significantly reduced, but the chemical elements analysed with improved detection limits were considerably extended; additionally, geochemical anomalies were better resolved. Notwithstanding this evolution, data obtained in early soil geochemical surveys (notably by the Serviço de Fomento Mineiro) are still useful in the development of preliminary approaches at a regional scale. Over the years, many studies were made for exploration and environmental assessments, the most relevant of them reported in this chapter. Natural distributions of chemical elements were also identified in these studies as background (if pristine conditions are present) or baseline (depending how disturbed is the area covered by the sampling survey) values. Large part of IPB was, and still is, subjected to poly-metallic mineral exploration or mining, being also the focus of environmental evaluation and/or remediation projects on particular areas that, being the target of long-lasting human intervention, represent paradigmatic case-study examples. The exploration and exploitation works carried out by national and foreign private companies were, and still are, very important for innovative achievements in IPB along with copious contributions from the Portuguese R&D public institutions. Presently, LNEG possesses a vast quantity of geochemical data that can be provided for companies that wish to start their activity in the IPB; some of these datasets are compiled to a unique integrative map also presented in this work. Stream-sediments geochemistry, hydrogeochemistry and lithogeochemistry (of outcropping rock and drill-core samples) represent also important sources of geochemical data in regional or detailed studies over specific target areas in the IPB. However, these techniques are beyond the scope of the present paper which aimed at providing a general overview of the importance of soil geochemistry studies in the current knowledge of the IPB.
- Sources, background and enrichment of lead and other elements : Lower Guadiana RiverPublication . Batista, Maria Joao; de Oliveira, Daniel Pipa Soares; Abreu, Maria Manuela; Locutura, Juan; Shepherd, T. J.; Matos, João Xavier; Bel-Lan, A.; Martins, Luís Plácido
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