Suchergebnisse

Shearband boudins (asymmetric boudins showing slip along the inter-boudin surface, which is synthetic with respect to the bulk shear sense) are ubiquitous and well-exposed in HT simple shear zones. The present work aims to extend the methodology of analysis of shearband boudins developed by Goscombe and Passchier (2003). Such shearband boudins represent complex objects that require an adequate methodology for unambiguous kinematic interpretation. We propose new geometric parameters (Bbs, B-t, c', D', d, ψ') in order to describe and identify, with confidence, the kinematics of boudinage in this particular geological framework. The key-observation for kinematic interpretation in simple shear regimes is the boudin axis (Lb) that is commonly present, excluding the necessity to identify the regional stretching lineation (Lx) in the metasedimentary matrix. In monoclinic HT simple shear zones, this approach involves the use of a local displacement plane (Sx), which is always normal to the boudin axis (Lb). ; Partial funding to JP was provided by the Centro de Investigacao GeolUgica, Ordenamento e Valorizacao de Recursos that is supported by the Pluriannual program of the Fundacao para a Cilncia e a Tecnologia, funded by the European Union (FEDER program) and the national budget of the Portuguese Republic. Very insightful and helpful reviews were done by C. Fernandez (University of Huelva) and two reviewers, for which we are grateful. We want to acknowledge to T. Valente (University of Minho) for her suggestions that helped to simplify the manuscript structure and to A. McCaig (University of Leeds) for his final comments and English revision that significantly improved this ...

The supply of drinking water is one of the major concerns in semi-arid and arid climates, mainly in developing countries. The present study reviews the situation of the water supply in a West African coast country, the archipelago of Cape Verde, with focus on the most populous island (Santiago), regarding the rate of public coverage and the water quality. As main insights, the research indicates that at Santiago Island only 54% of the population has con- nection to the public network, while 24% uses wells, springs and other potentially non-potable sources. The region of São Domingos is one of the most critical, with only 6.5% of public supply, justifying the assessment of the water quality used by this population. With regard to water quality, the results of this study indicate that natural and anthropic factors are contributing to degradation of the water resources, with salinity, chloride, nitrates, and nitrites as major concerning pollutants. The insufficiency of the public supply in this island could be a reflection of the situation in other arid re- gions of Africa. Though the recent advances it is vital to continue or even increase with the interna- tional cooperation to provide for adequate water supply infrastructures. ; Nemias Moniz Goncalves avails to acknowledge Gulbenkian Scholarship Service from FCG (CALOUSTE GULBENKIAN FOUNDATION), for the granted individual scholarship, under the program of Postgraduate Scholarships for students of PALOP and East Timor - Stimulating research and professional appreciation, process Nº. 139758. The FCG has been an indispensable support in carrying out all academic activities. This work was also supported by the European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalização) - project ICT (UID/GEO/04683/2013) with reference ...

The evolution of less ductile layers embedded in a more ductile matrix under simple progressive shear in some geological structures, such as folding and asymmetric boudinage in the same direction, is a current trend in structural geology research. Aiming to study this subject, in this work a finite element method (FEM) is used to discretize a continuous medium as a point-mass model in which every node is subject to elastic and viscous forces. The dynamic equation of the present system takes into account both kinds of those forces driving the motion of each particle. In the herein developed model the system is subject to external shear forces applied to some nodes, resulting in a continuous flow of material. The balance between viscous and elastic constants is pursuit in order to characterize the evolution of the system. ; - The author Maria Antonia Forjaz acknowledges the funding supported by Portuguese Funds through FCT 'Fundacao para a Ciencia e a Tecnologia', UID/MAT/00013/2013. The author Jorge Pamplona is co-funded by the European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalizacao), project ICT (UID/GEO/04683/2013) with reference POCI01-0145-FEDER-007690 and national funds provided by Fundacao para a Ciencia e Tecnologia. The authors Teresa de Lacerda-Aroso and Antonio Mario Almeida acknowledge the support of the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding ...

In this work the evolution of visco-elastic systems under external stress is addressed. An approach as a mixed complementary eigenvalue problem to model the geological folding and asymmetric boudinage in the same direction is considered. A matricial dynamics equation that comprehends elasticity and viscosity matrices is presented. An algorithm to connect material points and to build the adjacency matrix has been developed. Numerical results for a set of 16 nodes are shown. ; Portuguese Funds through FCT - 'Fundação para a Ciência e a Tecnologia', UID/MAT/00013/2013. European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalização), project ICT (UID/GEO/04683/2013) with reference POCI-01-0145-FEDER-007690 and national funds provided by Fundação para a Ciência e Tecnologia. Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. ...

In viscous materials systems, time and stress dependent instabilities often occur. The evolution of visco-elastic systems under external stress has already been modeled by applying matricial dynamic equations comprehending elasticity and viscosity matrices. In this study we report a novel formulation for such kind of systems as a nonlinear quadratic eigenvalue problem evolving from an already defined adjacency matrix. A four mass-spring damped system is presented as case study. ; The author Maria Antónia Forjaz acknowledges the funding supported by Portuguese Funds through FCT - 'Fundação para a Ciência e a Tecnologia', UID/MAT/00013/2013. The author Jorge Pamplona is co-funded by the European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalização), project ICT (UID/GEO/04683/2013) with reference POCI-01-0145-FEDER-007690 and national funds provided by Fundação para a Ciência e Tecnologia. The authors António Mário Almeida and T. de Lacerda–Arôso acknowledge the support of the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. ...

In viscous material systems,time and stress dependente instabilities often occur. The evolution of visco-elastic systems under external stress has already been modeled by applying a matricial dynamics equation comprehending elasticity and viscosity matrices. In this study we report a novel formulation for such kind of systems in an overdamped regime as a nonlinear quadratic eigenvalue problem. The results presented were obtained after solving the eigenvalue equation of several sets of discrete damped mass-spring systems. ; The author Maria Antónia Forjaz acknowledges the funding supported by Portuguese Funds through FCT Fundação para a Ciência e Tecnologia, UID/MAT/00013/2013. The author Jorge Pamplona is co-funded by the European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalização), project ICT (UID/GEO/04683/2013) with reference POCI-01-0145-FEDER-007690 and national funds provided by Fundação para a Ciência e Tecnologia. The authors Anto´nio Ma´rio Almeida and T. de Lacerda–Arôso acknowledge the support of the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The research of Lu´ıs M. Fernandes was partially supported in the scope of R&D Unit UID/EEA/50008/2013, financed by the applicable financial framework (FCT/MEC through national funds and when applicable co-funded by FEDER PT2020 partnership agreement). ...

The rare earth elements (REE) along with iron and manganese distribution in ochre-precipitates and wetland soils in a passive system for acid mine drainage treatment (Jales, Portugal) was studied. The results obtained by instrumental neutron activation analysis showed a higher incorporation of the light REE (particularly La and Ce) by the ochre-precipitates resulting from the mine water-limestone interaction. These fluffy materials influence the entrance of the first wetland where a correlation between Fe and La and Ce was found. Then Mn phases appear to play a more important role controlling REE distribution in the remaining area of the wetland soils. ; Thanks to EDM (Empresa de Desenvolvimento Mineiro, S.A.) for providing access to the water treatment plant, and to the staff of the Portuguese Research Reactor (RPI) of CTN/IST. C2TN authors gratefully acknowledge the FCT (the Portuguese Science and Technology Foundation) support through the UID/Multi/04349/2013. This work is co-funded by European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalização), project ICT (UID/GEO/04683/2013) with reference POCI-01-0145-FEDER-007690 and national funds provided by FCT. ...

The geochemical evolution of acid mine drainage results in secondary minerals that play a key role in the environmental behavior of the mine wastes. The present work is focused on these newly formed minerals at the Penedono waste dump, characterized by fine-grained tails with pyrite and arsenopyrite. Mineralogical study led to an inventory of secondary phases, comprising soluble sulfates, scorodite, and oxyhydroxysulfates. In addition, there is amorphous Fe, As rich-nanoprecipitates. Jarosite and scorodite are abundant minerals, acting as cement for encrusting tails in Fe and As-rich hardpans. These hard structures are relatively insoluble, retaining toxic elements, thereby contributing to natural attenuation of mining contamination associated with the sulphide wastes. ; European Union through the European Regional Development Fund, based on COMPETE 2020 - project ICT (UID/GEO/04683/2013) with reference POCI-01-0145- FEDER-007690 and project Nano-MINENV number ...