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Instituto Dom Luiz
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From source to surface: clues from garnet-bearing Carboniferous silicic volcanic rocks, Iberian Pyrite Belt, Portugal
Publication . Cravinho, André; Rosa, Diogo; Relvas, Jorge M.R.S.; Solá, A. Rita; Pereira, Inês; Paquette, J. L.; Borba, M. L.; Tassinari, Colombo C. G.; Chew, David; Drakou, Foteini; Breiter, Karel; Araújo, Vítor
ABSTRACT: This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca. 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 degrees C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at ca. 356.8 +/- 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca. 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (ca. 770 degrees C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts.
Biogas reforming as a sustainable solution for hydrogen production: Comparative environmental metrics with steam-methane reforming and water electrolysis in the Portuguese context
Publication . Bento, Cláudia; Lopes, Tiago; Rodrigues, Pedro; Gírio, Francisco; Silva, Carla
ABSTRACT: This study delves into the dynamics of hydrogen production, with a specific focus on biogas reforming (BGSMR) for hydrogen generation. It compares the environmental impact of this solution with hydrogen production from natural gas-steam reforming (NGSMR) and commercial electrolysis in the Portuguese context. Various metrics, including carbon footprint, water depletion, energy utilization, and waste valorization are employed for a comprehensive comparison. The assessment explores the impact of operational parameters and different off-gas combustion scenarios, incorporating water recycling practices. Due to challenges in obtaining detailed data on the actual reforming process, the study relies on process simulation techniques, primarily using DWSIM. Commercially available data for water electrolysers were used for comparison. In the context of decarbonizing power systems, hydrogen from water electrolysis emerges as a competitive option only in a scenario where the power system is 100% reliant on renewable sources, particularly with respect to the carbon footprint metric. Biogas systems, characterized by near-zero carbon emissions, stand out as a favourable option from the near future to the long run. This research contributes valuable insights into the dynamics of hydrogen production, shedding light on environmentally viable alternatives across a range of power system scenarios.
Carbon footprint assessment of microalgal biomass production, hydrothermal liquefaction and refining to sustainable aviation fuel (SAF) in mainland Portugal
Publication . Pires, Renata; Silva, Tiago; Ribeiro, Cláudia; Costa, Luis; Matos, Cristina T.; Costa, Paula; Lopes, Tiago; Gírio, Francisco; Silva, Carla
ABSTRACT: Industrial liquid effluents (e.g., from fertilizer industry) and flue gas streams (e.g., CO2-rich, from cement industry) arise as an opportunity for waste valorization. Microalgae are suitable biomass for assimilating both effluents at the cultivation stage. Under a biorefinery concept, given the urge for energy transition in the aviation sector, this research explores the transformation of a microalgae consortium grown at an industrial site in Portugal and its subsequent harvesting, hydrothermal liquefaction (HTL), and bio-oil refining. A life cycle assessment (LCA) approach is undertaken with two functional units (FU): 1 kg of microalgae dry-cell weight (dw) and 1 MJ of bio-jet fuel. The latter follows an attributional approach with energy allocation for comparison with the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) guidelines. HTL is based on data from bench-scale experiments and literature, whereby the Petroleum Refinery Life Cycle Inventory Model (PRELIM) is used to mimic bio-oil refining. Following this approach, achieving Sustainable Aviation Fuel (SAF) compliance requires net-zero electricity (0 gCO2eq/kWh), with an HTL bio-oil yield of 55.6 % dw (the maximum observed), a minimum refining bio-jet fuel yield of at least 16 %. Alternatively, an HTL bio-oil yield of 36.9 % dw (the median observed) with a refining efficiency of at least 24.3 %.
Ediacaran and early-palaeozoic bimodal volcanism in the Ossa-Morena Zone, SW Iberian Massif: New clues for intraplate rifting shortly after the Cadomian Orogeny
Publication . Cachapuz, P.; Chichorro, Martim Afonso; Bento dos Santos, Telmo; Carvalho, D.; Linnemann, Ulf; Zieger-Hofmann, M.; Zieger, J.; Dantas, E.; Santos, R. V.; Moita, Patrícia; Beltrame, M.; Solá, A. Rita; Díaz-Azpíroz, M.; Fernández, C.
ABSTRACT: This study focuses on bimodal meta-volcanic rocks present in the Iberian Massif, in the Evora-Aracena Metamorphic Belt of the Ossa-Morena Zone (OMZ), near the boundary with the South Portuguese Zone. New petrological, geochemical (whole-rock and Sr-Nd isotopes) and LA-ICP-MS U-Pb zircon geochronology data are presented to track the magmatic evolution of both felsic and mafic rocks and their respective geodynamic setting during the transition between the Cadomian Orogeny and subsequent Palaeozoic rifting events. Our research shows that the Evora-Aracena Metamorphic Belt (EAMB) in the southwestern OMZ possesses a significant record of the transition between the Cadomian and Variscan cycles. U-Pb geochronological data confirm the existence of both felsic and mafic Ediacaran igneous rocks (546 and 556 Ma, respectively), a novelty in the region. The Cadomian-related felsic rocks show geochemical similarities to meta-felsic rocks formed during the initial phases of the Cambrian rifting event, namely very negative epsilon Nd values (-10.1 to -11.8), depleted HREE patterns and orogenic signatures. Such similarities imply that meta-felsic rocks formed in the earliest stages of the Cambrian Rift-to-Drift event resulted from a shallower melting. Moreover, meta-felsic rocks formed in the early stages of the Cambrian rifting (525 Ma) present a significant amount of Ediacaran aged zircons, whereas the Cadomian-related counterparts display a few discordant Cambrian ages, likely a consequence of Pb-loss. This indicates that the convergent, subduction-related regime that prevailed during most of the Cryogenian-Ediacaran times along the boundaries of NW Gondwana was swiftly supplanted by a rift-dominated regime during the Cambrian, with no substantial gap between these two thermal events. Meanwhile, meta-felsic rocks formed during the Rift-to-Drift (525-480 Ma) event exhibit progressively higher epsilon Nd values (-5.0 to +3.0), HREE-enrichment, as well as anorogenic signatures, denoting an increasing contribution of mantle-derived melts. This increasing mantle contribution eventually led to the occurrence of bimodal magmatism in the Middle Cambrian Main Rift event. Such Cambrian mafic rocks, unlike the Ediacaran mafic rocks that present flat REE patterns and continental arc signatures, display varying degrees of LREE enrichment and N-MORB to E-MORB signatures.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDP/50019/2020