28 documents found, page 1 of 3
Strain partitioning in transpression; a major feature in the evolution of the I...
Dias, Rui; Araújo, Alexandre; Couto, Helena; Cruz, Cláudia; Ferreira, Joana; Gonçalves, Ana Marta; Lima, Alexandre; Lopes, Luís; Moreira, NoelAs the wavy pattern of fold belts is a common feature, since its recognition, the transpressive regimes were expected to be a pervasive mechanism on their evolution. Nevertheless, even in regions where oblique shortening is inferred, typical structures of transpression (e.g. transected cleavage and en echelon folds, shear or veins) are often absent. Instead, what is frequently observed is the juxtaposition of n...
Caracterização mineralógica do jazigo de ferro de Vila Cova (Marão)
Lopes Dias, Joana Mafalda; Vianez, Ricardo; Sant'Ovaia, Helena; Guedes, Alexandra; Cruz, Cláudia; Ferreira, Joana; Noronha, FernandoRESUMO: A caracterização mineralógica de amostras do jazigo de Vila Cova, situado no norte de Portugal, foi realizada a partir do estudo petrográfico, metalográfico, de catodoluminescência e de microscopia eletrónica de varrimento com espectroscopia por dispersão de energias. Assim, foram identificados minerais como quartzo, clorite, magnetite, pirite, arsenopirite, calcopirite, galena, tetradimite, rútilo, zir...
Caracterização mineralógica do minério de ferro dos jazigos de Cabeço de Mua e ...
Vianez, Ricardo; Lopes Dias, Joana Mafalda; Guedes, Alexandra; Sant'Ovaia, Helena; Ferreira, Joana; Cruz, Cláudia; Noronha, FernandoRESUMO: tecnologia e das infraestruturas de um país. Com o intuito de melhor conhecer os minérios de ferro de Portugal, especificamente dos jazigos de Cabeço da Mua e da Carvalhosa, foram efetuados estudos petrográficos, metalográficos e de microscopia eletrónica de varrimento com espetroscopia por dispersão de energias (MEV-EDE). Os minerais principais identificados foram quartzo, hematite e goetite, havendo a...
Golden Years: Mineralogical associations in the Casa-Novas orogenic gold deposi...
Nogueira, Pedro; São Pedro, Diogo; Roseiro, José; Sant'Ovaia, HelenaGold mineralisations are frequently associated with orogenic belts where accretionary and collisional processes create favourable conditions for mineral deposit formation. These belts, subject to metamorphism and deformation, host significant gold resources in structurally controlled hydrothermal systems. Among the various models explaining gold transport and deposition, the role of bismuth (Bi)-rich fluids has...
Tectonic Evolution of Portuguese Variscan Granites: Insights from Anisotropy of...
Sant'Ovaia, Helena; Cruz, Claudia; Gonçalves, Ana; Nogueira, Pedro; Noronha, FernandoThe anisotropy of magnetic susceptibility (AMS) data from 19 Portuguese Variscan granite plutons, spanning 320–296 Ma, has been consolidated and reinterpreted. This comprehensive dataset, including 876 sampling sites and over 7,080 AMS measurements, provides new insights into the tectonic evolution of the region. Magnetic susceptibility (Km) values range from 30 to 10,436 × 10 SI, with most granites exhibiting ...
New insights from an emplacement model for the Santa Eulália Plutonic Complex (...
Cruz, Claudia; Nogueira, Pedro; Máximo, Jaime; Noronha, Fernando; Sant'Ovaia, HelenaThe Santa Eulália Plutonic Complex is formed by two main granites: G0 and G1. The G0 granite hosts metasedimentary carbonate and pelitic rocks (roof pendants) and elongated masses of mafic–intermediate rocks (the M-group). The host rocks form a diverse sequence of igneous, metasedimentary and metamorphic rocks. The study area is constrained by Variscan structures formed in a transpressional/transtensional sinis...
Physicochemical Properties of Fe-Bearing Phases from Commercial Colombian Coal Ash
Santos, Ana Cláudia; Cruz, Cláudia; Font, Eric; French, David; Guedes, Alexandra; Moreira, Karen; Sant'Ovaia, Helena; Vieira, Bruno J. C.High amounts of coal combustion products, such as fly ash and bottom ash, are generated every year; however, only 64% are used, which means that a significant part is landfilled despite containing valuable materials such as ferrospheres, which may be used as catalysts, substituting critical raw materials (e.g., platinoids). In commercial coals, pyrite contents are reduced as a pre-combustion S-emissions control...
Suscetibilidade magnética em sequências carbonatadas silúricas da Ibéria: prime...
Silvério, Gonçalo; Cruz, Cláudia; Sant'Ovaia, Helena; Moreira, NoelMagnetic susceptibility studies (magnetostratigraphy) are a tool for correlating stratigraphic sequences of similar ages, especially for situations where biostratigraphy is not applicable or presents little precision in the range of ages that can be obtained from it. These studies are also used as a tool for the correlation of paleoclimate events on a regional or global scale. In this work, three Silurian seque...
Geochemistry of Soils from the Surrounding Area of a Coal Mine Waste Pile Affec...
Santos, Patrícia; Espinha Marques, Jorge; Ribeiro, Joana; Mansilha, Catarina; Melo, Armindo; Fonseca, Rita; Sant'Ovaia, Helena; Flores, DeolindaCoal mining can generate organic and inorganic contaminants that can be disseminated in the surrounding soils by leaching and/or aerial deposition. This study aims to identify and characterize the physicochemical and geochemical changes promoted in soils from the surrounding area of a self-burning waste pile in an abandoned coal mine. A soil sampling campaign was conducted bordering the waste pile, comprising t...
Suscetibilidade magnética de xistos negros associados a mineralizações de Cu em...
Laranjeira, Vanessa; Ribeiro, Joana; Moreira, Noel; Nogueira, Pedro; Sant'Ovaia, Helena; Flores, DeolindaNa Zona Ossa-Morena (ZOM) estão identificados depósitos de Cu associados a filões mineralizados cuja génese resultou da circulação de fluidos hidrotermais. Espacialmente associados a estes depósitos ocorrem xistos negros (XN) datados do Silúrico. Este trabalho tem como objetivo determinar a suscetibilidade magnética de amostras de XN, de afloramento e sondagens, ocorrentes na ZOM e correlacionar as propriedades...