GF - Comunicações em actas de encontros científicos internacionais
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- Heat Flow Density Estimations in the Portuguese Northern Hercynian Massif using Silica GeothermometryPublication . Correia, Antonio; Ramalho, ElsaABSTRACT: Surface heat flow density (HFD) estimates in the Portuguese northern Hercynian Massif are difficult to obtain using the usual Fourier method. As a matter of fact, this zone is mostly composed by granitoid and metamorphic rocks, and most wells drilled there are too shallow for reliable HFD calculations; furthermore, HFD estimates are scarce and their geographical distribution is still very irregular. All these conditions imply that a HFD map for this region must be obtained using alternative methods, such as the silica geothermometry method. Under certain conditions, the use of silica geothermometers to estimate HFD in mineral waters has proved to be an effective way to understand and establish the thermal regime in areas with scarce conventional HFD determinations. Because temperatures obtained with silica geothermometry are related to deep thermal conditions in the crust and to water-rock equilibrium, a regional HFD analysis may be carried out using those temperatures. The silica geothermometer, developed by Truesdell in 1976 (Truesdell, 1976), give good results for low SiO2 concentrations, which is the case for the Portuguese northern Hercynian Massif, and is applied to more than 30 samples of mineral water occurrences reported for the zone. This number of samples, even though small, is considerably higher and more evenly distributed than conventional HFD estimates for the same area. Application of silica geothermometry to northern Hercynian Massif waters shows a discrete reservoir temperature zoning, ranging from about 45 ºC, in its southwest limit, to more than 120 ºC, towards its northeast limit. Using temperatures obtained by silica geothermometry and heat flow density values calculated through the conventional method in an area of 1º x 1º in the study zone, an empirical linear relationship between HFD and temperatures obtained by silica geothermometry is obtained and used to construct a HFD map for the Portuguese northern Hercynian Massif. The resulting HFD map is compared with the general geological and structural framework, and an attempt to a geothermal characterisation of the Portuguese northern Hercynian Massif is made.
- GeoERA´s contribution towards resilience in Europe’s raw materials supply chainsPublication . Wittenberg, Antje; De Oliveira, Daniel Pipa Soares; González, Javier; Flindt Jørgensen, Lisbeth; Held, TomThe well-being of society and the interdependencies of national economies depend heavily on reliably functioning supply chains as the COVID-19 pandemic proved this long-known statement in everyone's daily life. None of the supply chains can do without the mostly mineral raw materials. The United Nations sees raw materials as the key component for achieving all 17 Sustainable Development Goals (SDGs).
- Three decades of reflection seismic surveying at Neves-Corvo, PortugalPublication . Donoso, George; MALEHMIR, Alireza; Carvalho, Jorge; Araújo, VítorSUMMARY: The Neves-Corvo is arguably the largest and one of the most important volcanogenic-hosted massive sulphide (VMS) endowments in the world. In the last three decades three seismic acquisition programs have been carried out in the area. In 1996, six profiles covering the area, with a special interest in the tier-1 Lombador deposit. Reprocessing of this dataset was done in 2019 and showed the relevance of revisiting legacy data using current tailored processing workflows. In 2011, a 24 km2 3D survey was done with the intention of producing new targets and in particular with the discovery of the Semblana deposit in 2010, the 3D dataset showed its potential beyond the earlier 2D surveys. In 2019, new technologies for seismic exploration were tested, the new seismic survey consisted of two perpendicular 2D surface profiles positioned above the known Lombador deposit, additionally source points were activated inside the exploration tunnels and simultaneously recorded on the surface, which provided an improved velocity model for migration and time-to-depth conversion. The objective of this study is to provide an overview of these surveys and present the latest results of revisiting the 2011 3D seismic data.
- Updated geothermal assessment of Lower Cretaceous aquifer in Lisbon region, PortugalPublication . Marrero Diaz, Rayco; Ramalho, Elsa; Costa, Augusto Marques da; Ribeiro, Maria Luísa; Carvalho, João; Pinto, Carlos C.; Rosa, Diogo; Correia, Antonio
- Earthquake mitigation in the Lisbon and Lower Tagus Valley area, PortugalPublication . Carvalho, João; Dias, Ruben Pereira; Pinto, Carlos C.; Cunha, Taigo A.; Leote, Jaime; Vilanova, Susana; Narciso, João; Borges, José Fernando; Ghose, Ranajit
- Earthquake mitigation in the Lisbon and Lower Tagus Valley area, PortugalPublication . Carvalho, João; Dias, Ruben Pereira; Pinto, Carlos C.; Cunha, Tiago A.; Leote, Jaime; Vilanova, Susana; Narciso, João; Borges, José Fernando; Ghose, Ranajit
- Integration of seismic, well, potential-field and geological data for ore prospecting in the Iberian Pyrite BeltPublication . Carvalho, João; Sousa, Pedro; Matos, João Xavier; Pinto, Carlos C.Ore prospecting using gravimetric and magnetic data has become one of the traditional approaches in the last decades, often complemented with electric and electromagnetic methods. However, due to the problem of non-uniqueness inherent to potential-filed modelling, constrains provided by structural methods such as seismic reflection are often used. During the exploration of massive sulphide polimetallic minerals in the Iberian Pyrite Belt Figueira de Cavaleiros sector, located in the Sado Tertiary Basin, several gravimetric and magnetic anomalies were considered as interesting targets. In order to reduce ambiguity of the gravimetric modelling and to confirm the geological model of the area, two seismic reflection profiles were acquired. The interpretation of these profiles was assisted by three mechanical boreholes, two of them located in the research area, in order to make a seismostratigraphic interpretation. Unfortunately, the gravimetric modelling suggests that the anomaly has a lithological and structural origin and is not related with massive sulphides. Nevertheless, a good agreement between the seismic and potential-field data was achieved and new insights into the geological model for the region were obtained form this work, with accurate data about the Tertiary cover and Palaeozoic basement.
- New approach on the gravity data of the Lagoa Salgada structure, Iberian Pyrite Belt, PortugalPublication . Represas, Patricia; Matos, João Xavier
- Estimation of imageable dip range of target structures in interferometric salt flank imaging with limited illuminationPublication . Loureiro, A.; Van der Neut, J.; Alves, Daniela; Carvalho, João; Afilhado, Alexandra; Draganov, D.; Matias, L.; Martins, T.
- The signature of a small-throw fault affecting unconsolidated sediments in S-wave reflection seismic dataPublication . Carvalho, João; Ghose, Ranajit; Loureiro, A.