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- Natural Stones from Portugal : Proposal for harmonizing Commercial NamesPublication . Carvalho, Jorge; Carvalho, Cristina Isabel Paulo; Lopes, Luis; Silva, António; Santos, Catarina; Sousa, Luís; Martins, Ruben; Marques, CéliaABSTRACT: Over the years, the Portuguese Geological Survey – LNEG, has been dedicated to the characterization of Portuguese natural stones. Today, a newly updated LNEG web portal contains information on 149 natural stones, which are known by their unique trade names. Many of these names integrate the EN 12440 - Natural Stone - Denomination Criteria standard, but others do not. Furthermore, there many other names used to identify natural stones that are traded today and that do not integrate the LNEG web Portal or the EN 12440. This work presents a harmonization proposal for the commercial denomination of the Portuguese natural stones. It is a working basis for a final list that must be submitted to ISO/Technical Committee 118 – Natural Stones.
- Depth estimation of pre-Kalahari basement in Southern Angola using seismic noise measurements and drill-hole dataPublication . Carvalho, João; Alves, Daniela; Borges, José Fernando; Caldeira, Bento; Cordeiro, Domingos; Machadinho, Ana; Oliveira, Álvaro; Ramalho, Elsa; Rodrigues, José Feliciano; Llorente, J.; Ditutala, M.; Lobón, Jose Luis Garcia; Máximo, J.; Carvalho, Cristina Isabel Paulo; Labaredas, José; Ibarra, P.; Manuel, JoséABSTRACT: The remote Southern region of Angola is covered by siliciclastic Kalahari Cenozoic formations that host underground aquifers of great importance to local populations affected by water scarcity problems. These aquifers are well developed where Kalahari sands reach appropriate thicknesses. On the other hand, at the eastern end of this area, regional aeromagnetic data recently acquired suggested the possibility of the continuity of the geological structures of the Lufilian Arc, sited in the nearby Zambia and Congo, southwestwards into Angola under the Kalahari formations. Once the Lufilian Arc is associated with the presence of the so-called Central African Copperbelt, this possibility increased the interest in determining the depth to Pan-African rocks under the Kalahari basin. To estimate the thickness of Kalahari formations in this area of difficult access and poor logistics, an expedited and non-invasive geophysical method was needed. Seismic noise and the single-station Nakamura technique were chosen, but due to the large distance of the study area from the ocean, one of the major sources of seismic noise, a test survey was acquired in the Cuvelai region to assess the signal quality, where the data was calibrated using available drill-holes. >170 points of seismic ambient noise were later acquired and the horizontal/vertical (HVSR) amplitude versus frequency curves were 1D inverted for the best velocity/density model for each station. The results were compared with 1D inverted legacy vertical electrical soundings reprocessed and validated in this work, showing similar depth-to-basement, while interpreted velocities/densities of geological formations were sampled and confirmed with measurements. A depth-to-basement map was produced using seismic information, mechanical soundings, and geological information. Despite the relatively reduced geographical area covered, the map presents valuable information for hydrogeology and mineral exploration purposes and agrees with a previously available coarser map of Kalahari thickness and with observations from geological surveys simultaneously conducted at the time of the seismic surveys.
- A Pedra Natural Portuguesa : Proposta de harmonização de Designações ComerciaisPublication . Carvalho, Jorge; Carvalho, Cristina Isabel Paulo; Lopes, Luis; Silva, António; Santos, Catarina; Martins, Ruben; Marques, Célia; Sousa, LuísRESUMO: No início dos anos 80 do século passado, o LNEG – Laboratório Nacional de Energia e Geologia (Serviços Geológicos de Portugal), através das suas instituições públicas antecessoras, deu início à caracterização e à inventariação das rochas ornamentais extraídas em Portugal. Deste trabalho inaugural resultou o primeiro Catálogo de Rochas Ornamentais Portuguesas, publicado em 4 volumes entre 1983 e 1994, complementado por 8 fichas técnicas editadas entre 1995 e 2000. Em 2002, a 1ª versão em formato digital do catálogo começou a ser desenvolvida, tendo sido incluída no site do LNEG como o Portal das Rochas Ornamentais Portuguesas – ROP. Foi atualizado em 2021 (https://geoportal.lneg.pt/pt/bds/rop/), englobando toda a informação contida no catálogo, além de novas funcionalidades como a “pesquisa por critérios”, tais como a designação comercial, o município de exploração, a cor, assim como diversas características tecnológicas. Ao longo dos anos, novas pedras foram acrescentadas ao ROP, que atualmente contém a informação relativa a 149 litótipos comerciais portugueses.