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Projeto de investigação
Institute Dom Luiz
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Sistema elétrico futuro baseado em renováveis e a sua dependência da variabilidade climática e da evolução do consumo
Publication . Figueiredo, R.; Nunes, P.; Brito, M.C.
RESUMO: A transição para sistemas elétricos baseados em renováveis tem sido crítica para o combate às alterações climáticas. Tal contribui para uma maior vulnerabilidade dos sistemas a variações do clima e do consumo elétrico no futuro. Com base nisto, este trabalho analisa o impacto que climas futuros e cenários de consumo terão num sistema elétrico com elevada penetração de renováveis. O caso de estudo é Portugal em 2050. Utilizando uma ferramenta de modelação com base horária, o sistema é simulado para cerca de 500 projeções climáticas (RCP4.5 e RCP8.5) e para dois cenários de evolução do consumo. Conclui-se que o cenário de elevado consumo é o mais afetado pelo clima, mostrando uma variação da fração de produção renovável do sistema elétrico de referência de 55 para 78% (79 e 93%, na configuração ótima) sob condições desfavoráveis e favoráveis, respetivamente. Para o cenário de baixo consumo, a fração renovável varia entre 89 e 93% (92 e 95%, na configuração ótima) sob condições desfavoráveis e favoráveis, respetivamente.
Age dependent variation of the magnetic fabric of dike swarms and implications for the volcanic structure of ocean islands: the example of the Maio Island, Cabo Verde archipelago
Publication . Moreira, Mário; Mata, João; Madeira, José; Represas, Patricia; Martins, Sofia
ABSTRACT: Magnetic fabric analysis of dikes is a powerful technique when assessing magma transfer processes. This study presents an integrated analysis combining magnetic susceptibility and anisotropy of magnetic susceptibility, magnetic mineralogy, geochemistry and new 40Ar/39 Ar dating of dikes intruding formations ranging from the Lower Cretaceous to the Miocene on the island of Maio, in the Cabo Verde archipelago. We show that the dikes, dated at ≈9.2 Ma, intruding the younger Miocene Casas Velhas formation, display a Ti-rich titanomagnetite composition, higher whole-rock TiO2 content and very high magnetic anisotropy. They are clearly distinguished from the dikes, ranging in age from ≈9.3 to 11.3 Ma, intruding older formations, which show a predominantly Ti-poor titanomagnetite composition with multiple magnetic phases, lower whole-rock TiO2 concentration, higher range of magnetic susceptibilities and very low anisotropy. Magnetic fabric is predominantly normal with no significant imbrication relative to the dike margins. Numerical analysis of fabric shows a dominant coaxiality between the magnetic lineation and the preferred orientation of opaques and phenocrystals suggesting that magnetic lineation is, therefore, the proxy of the magmatic flow axis orientation. Based on the orientation of the magnetic fabric, we infer that magmatic flow within the studied dikes is predominantly vertical. The differences observed between the younger dikes and all other dikes may be related to magma sourced from distinct magma chambers. One, probably shallow, underneath the Casas Velhas fm in the southwest of the island, which would explain the very high values of magnetic anisotropy and the inferred vertical flow, and another located in a central position in the island, responsible for the dikes intruding the older formations. The location of such magma reservoirs and the dikes ages suggest a hypothetical migration with age of the magmatic sources that fed the dikes from the central part of the island to the southwest region. The magnetic and mineralogical heterogeneities of the dikes intruding older Lower Cretaceous formations may also be a result of a wider age range of the intrusions.
Terrestrial environmental change across the Permian-Triassic boundary in the Karoo Zambezi Basin, Mozambique: Integrating palynological, sedimentological and carbon isotope evidence
Publication . Fernandes, Paulo; Pereira, Zélia; Spangenberg, J. E.; Silva Mendes, Márcia Cristina; Lopes, Gilda; Jorge, Raul C. G. Santos; Albardeiro, Luís; Font, Eric; Adatte, T.; Vennemann, T.; Marques, J.
ABSTRACT: The Permian-Triassic boundary (PTB; ca. 252 Ma) marks the most severe biotic crisis in Earth history, yet high-resolution terrestrial records from southeastern Gondwana, outside the Main Karoo Basin of South Africa, remain scarce. We present a multidisciplinary investigation of borehole CIMT-014 from the N'Cond & eacute;dzi Coalfield, Mozambique, which preserves a near-continuous continental succession spanning the PTB within the Karoo Zambezi Basin. Sedimentological, palynological, palynofacies, total organic carbon (TOC), and organic carbon isotope (delta(13)Corg) analyses were integrated to reconstruct environmental, ecological, and carbon-cycle changes across the transition. The uppermost Permian Matinde Formation comprises organic-rich floodplain mudstones, siltstones, and thin coal seams deposited under warm, humid conditions and dominated by Glossopteris-associated gymnosperm floras. Crossing the PTB, these deposits are abruptly replaced by conglomeratic, lacustrine, and fluvial sediments of the C & aacute;dzi Formation. Palynological data document a marked decline of glossopterid and other gymnosperm pollen, followed by a short-lived increase in opportunistic lycophyte and fern spores. Concurrently, palynofacies shift from assemblages rich in non-opaque phytoclasts to assemblages dominated by opaque phytoclasts, while TOC values decline from >40 wt% in coal-bearing intervals to <0.2 wt% in the earliest Triassic succession. A pronounced negative delta(13)Corg excursion of approximately 5.4 parts per thousand occurs across the boundary interval, with values decreasing from -25.0 parts per thousand to a minimum of -30.4 parts per thousand. The magnitude, stratigraphic coherence, and association with floral turnover, cessation of peat formation, and fluvial reorganisation indicate that the isotopic carbon excursion records a major perturbation of the global carbon cycle rather than local diagenetic effects. The isotopic signal is consistent with widespread carbon-cycle disruption linked to Siberian Traps magmatism and associated greenhouse-gas emissions. Our results demonstrate that terrestrial ecosystems in southeastern Gondwana experienced profound ecological and environmental disruption during the end-Permian crisis and establish the Karoo Zambezi Basin of Mozambique as a key archive for correlating continental records of the PTB in Gondwana.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/GEO/50019/2019