Browsing by Author "Lopes, C."
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- CHRONIBERIA : ongoing development of a geochronological GIS database of IberiaPublication . Lopes, C.; Ferreira, A.; Chichorro, Martim; Pereira, Manuel Francisco Costa; Almeida, J. A.; Solá, A. Rita
- Chroniberia : the ongoing development of a geochronological GIS database of IberiaPublication . Lopes, C.; Ferreira, A.; Chichorro, Martim; Pereira, M. Francisco; Almeida, J. A.; Solá, A. Rita
- Decipher a multi-event in a non-complex set of detrital zircon U-Pb agesPublication . Ferreira, A.; Lopes, C.; Chichorro, Martim; Pereira, Manuel Francisco Costa; Solá, A. Rita
- Deciphering a multi-event in a non-complex set of detrital zircon U-Pb ages from Carboniferous graywackes of SW IberiaPublication . Ferreira, A.; Lopes, C.; Chichorro, Martim; Pereira, M. Francisco; Solá, A. RitaThe determination of U–Pb ages from detrital zircons of sedimentary rocks using LA-ICP-MS has been widely used for the purpose of provenance analysis. One problem that frequently arises is finding a population that appears to be non-complex despite several perceptible age peaks in its spectrum. These peaks are qualitatively defined by means of relative probability diagrams, or PDFs, but it is difficult to quantify their statistical significance relative to a zircon forming multi-event. Thus, can a multi-event in a non-complex set of detrital zircon U–Pb ages be deciphered and characterized? The aim of this study is to attempt to provide an answer to this question by means of statistical analysis. Its objectives are: a) to determine the best minimum number of zircon age populations (peaks), BmPs, b) for the characterization of each peak in terms of age and event duration; c) to compare the results obtained from two datasets showing similar zircon ages; and d) to demonstrate the usefulness of deciphering these BmPs. First, cluster analysis is carried out, aimed at grouping zircon ages into a set of consistent clusters. A Gaussian Kernel function is then fitted to each cluster and summed to obtain a theoretical PDFm (modeled probability density function). Finally, the selected modeled PDFm (that built on the BmPs) is that which reports the lowest number of peaks for which the difference as compared with the original gPDF (global probability density function) is equal to or below 5%. Deciphered BmP peaks can be characterized and used for characterizing and providing an understanding of related event(s). A geological interpretation, based on the results obtained, is attempted. This includes a robust measure for maximum age of deposition for both Cabrela and Mértola graywackes.
- Deciphering a multipeak event in a noncomplex set of detrital zircon U-Pb agesPublication . Ferreira, A.; Lopes, C.; Chichorro, Martim; Pereira, M. Francisco; Solá, A. Rita
- Planning the future exploitation of ornamental stones in Portugal using a weighed multi-dimensional approachPublication . Carvalho, Jorge; Lopes, C.; Mateus, António; Martins, L.; Goulão, M.ABSTRACT: Portugal is one of the world's leading producers of ornamental stones and, in the last 50 years, this economic sector registered an annual national average growth of 4%. However, the lack of land-use policies that effectively safeguard the access of extractive industry to the places where these resources occur, current and foreseen production is at risk, compromising the contribution of this sector to the national economy and to the supply of forthcoming generations. The multi-dimensional methodology reported in Mateus et al. (2017) was applied to describe the present-day situation, allowing to objectively identify the tracts hosting ornamental stone resources whose access should be safeguarded, therefore avoiding their sterilisation when confronted to other land-use options. A database on the available geological information concerning 65 ornamental stone tracts, covering 0.43% of mainland Portugal, was built. Among the 54 active exploitation centres and 11 potential areas (for which there is no production data), only 21 tracts (0.07% of mainland Portugal) were classified as of "public importance", meaning they have an intrinsic value that should by itself support a safeguarding decision on their current and future access. According to the weighed criteria used, several promising tracts were not included in this short group. However, these promising tracts do not overcame the threshold due to the shortage of data about regional exploration surveys or on the resource itself, which reflects difficulties in gathering harmonised geological information for all the listed tracts. Thus, two simulation scenarios were completed, corresponding to an increase in knowledge resulting from regional exploration or local, comprehensive geological studies. As a result of these simulated scenarios, the total number of tracts qualified as of "public importance" increased to 41 (0.24% of mainland Portugal). These results highlight the urgent need to supplement the available geological information, contributing to the establishment of a credible and stable mining plan for the Portuguese ornamental stones sector, thus strengthening its sustainability in the short and long term.
- Provenance analysis of Lower Palaeozoic siliciclastic rocks of the Southwestern Iberia (Ossa-Morena Zone) : distal shelf deposition on the North Gondwana passive marginPublication . Pereira, M. Francisco; Chichorro, Martim; Lopes, C.; Solá, A. Rita; Silva, J. Brandão; Hofmann, Mandy; Linnemann, Ulf
- Provenance analysis of Lower Paleozoic siliciclastic rocks of SW Iberia (Ossa-Morena Zone) : distal shelf deposition in the North Gondwana passive marginPublication . Pereira, Manuel Francisco Costa; Chichorro, Martim; Lopes, C.; Solá, A. Rita; Silva, J. Brandão; Hofmann, Mandy; Linnemann, Ulf
- SIORMINP : Plataforma de gestão e disponibilização de dados harmonizados dos Recursos Minerais PortuguesesPublication . Patinha, Pedro; Pereira, Aurete; Quental, Lídia; Filipe, Augusto; de Oliveira, Daniel Pipa Soares; Lopes, C.RESUMO: O SIORMINP integra dados relevantes sobre os recursos minerais conhecidos que disponibiliza à sociedade via geoPortal do LNEG. Contudo não é interoperável com sistemas de informação similares europeus. Assim, em projetos europeus é necessário harmonizar os dados de acordo com especificações próprias, que contemplam requisitos da Diretiva INSPIRE. Os dados extraídos do SIORMINP são transformados e armazenados em outras bases de dados, implicando redundância e inconsistência dos dados. Para obviar este paradigma foi criada uma Geodatabase INSPIRE centralizada, para armazenar os dados dispersos por outras bases de dados. O mapeamento entre distintas bases de dados foi executado com uma ferramenta ETL. O desenvolvimento de uma aplicação de BackOffice permitirá o carregamento descentralizado de novos dados na referida Geodatabase. A integração destas aplicações no novo geoPortal, em 2020, permitirá a evolução do SIORMINP para uma plataforma de gestão e disponibilização de dados sobre Recursos Minerais Portugueses harmonizado com a Europa.
- U-Pb detrital zircon ages during tectonic inversion: provenance analysis of siliciclastic sequences of the Ossa-Morena ZonePublication . Chichorro, Martim; Santos, Telmo M. Bento Dos; Solá, A. Rita; Lopes, C.; Cachapuz, P.SUMÁRIO: Análise de proveniência de sucessões detríticas da Zona de Ossa-Morena é reinterpretada a fim de demarcar os estádios de inversão tectónica do Ciclo Varisco. Zircões detríticos de unidades de Rift do Câmbrico médio-superior (Fm de Ossa, Fm de Fatuquedo) mostram não ter existido variações significativas das áreas fonte quando comparadas com os sedimentos ediacarianos, que refletem erosão/reciclagem da crosta Pan-Africana e do Arco Cadomiano, espelhando a herança típica do Norte do Gondwana. O padrão da Fm da Colorada grava o início da subducção, pois mostra que o soco da ZOM já está em inversão, embora ainda com exumação limitada dos depocentros em Rift do Câmbrico. Por sua vez, as curvas da Fm de Terena já são consistentes com exumação ativa e erosão/reciclagem subaérea das sequências vulcano-sedimentares sin-Rift, refletindo as primeiras fases colisionais variscas.