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Vol. XI, Fasc. 3/4 (1956)

Vol. XI, Fasc. 3/4 (1956)Category: Publications, Estudos, Notas e Trabalhos, 1950 to 1959
Data de publicação: 30 September, 2019


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1. Calcários Cristalinos da Região de Portel.
João Martins da Silva (19 pages)
Abstract: Dans le complexe cristallophyllien de la région de Portel s’alignent divers affleurements de roches calcaires, dans une bande orientée NW-SE, s’etendant sur près de 30 Km. Ce complexe comprend, outre des calcaires cristallins, des schistes métamorphiques, des amphibolites plus on mois altérées, et des leptynites. Des roches éruptives: tonalitiques, doléritiques et porphyriques affleurent dans la région, à côté de divers filons aplitiques et quartzeux. A l’extremité SE de cette zone, les roches cristallophylliennes sont recouvertes par des terrains palégéniques. Les formations anciennes semblent se disposer dans un système de plis isoclinaux, inclinés vers le quadrant SW. Les calcaires sont cristallins; la plupart sont à grain fin et de couleur blanche, jaunâtre, rosée, grisâtre, marron, violacé et gris plus ou moins foncé.En certains endroits on constate l’addition d’eléments ferro-magnésiens, parfois en grande quantité, de magnétite, ainsi que des rares cristaux de pyrite, extrêmement fins. Les résultats des analyses chimique effectuées ont permis de classer les calcaires.

2. Considérations sur la Geochimie de Blendes et de Galenes Portugaises.
J. M. Cotelo Neiva (32 pages)
Abstract: Le Professeur Alberto Brito (1955) a publié deux travaux de spectrochimie semi-quantitative, l’un sur des blendes, l’autre sur des galènes portugaises. (…)L’étude des résultats l’analyse spectrographique des éléments mineurs contenus dans les blendes et les galènes portugaises permet des interprétations et des considérations d’intérêt géochimique, géologique, métallogénique et applicables aussi à la prespection.
C’est à une partie des cette étude que ce travail a trait.
(…) Parcial Abstract

3. Géologie et Genése des Gisements de Manganese du “Baixo Alentejo”.
Fernando José da Silva (39 pages)
Abstract: In this work we deal with the manganese belds known to exist in the Baixo Alentejo, as well as similar beds of the Huelva Province in Spain, very much connected with the porphiritic rocks. Therefore, despite the different opinions on their origin, we think they can be attributed to a hydrothermal origin. The magmatic fluids must have risen throught the zones of structural weakness of the intwall rocks and on finding favourable temperature and pressure conditions, they deposited part of the substances in solution with partial metasomatosis of the rocks. The beds thus formed, from the morfologic point of view appear in veins, on a rosary form, with varying lengths, from tens to hundreds of meters, and sometimes, with continuous solutions.As the conditions of deposition, transport and solution of the manganese compounds and the silics are identical, apart from small details, the beds are, with a few exceptions, formed fundamentaly by jasper and manganese minerals, either disseminated in the middle of jasper or constituting pockets wich sometimes reach thousands of tons. It is in these pockets that the main value of the beds of the Alentejo manganese exists.

4. Jazigo de Ferro de Guadramil.
J. A. da Cunha Gouveia (27 pages)
Abstract: There is an on deposit at the NE end of Portugal, the Guadramil deposit, where the Serviço de Fomento Mineiro have carried out a wide research plan. The results of the first works were published in this review, vol. VI n.º 1-4, with the title «Notícia sobre o valor económico do jazigo de Guadramil (Trabalhos de reconhecimento)».It was stated there that it was a deposit constituted of a layer of sideritic ore changed to limonite near the surface; hypoteses regarding the structure were suggested and the proved reserves until then determined were indicated with regards to limonite as well as siderite and was foreseen that the latter would be largely increased with the research work still in course. This actually hapenned as it is shown in this report which describes the work carried out after the publication of the above mentioned report. On the whole the two reports constitue the final report of all the works.
The work carried out and the elements obtained on the structure of the bed made it possible to calculate the reserves with accuracy enough. The total reserves reach 5,5 million tons, 1 million being concerned to lomonite. Of the 4,5 million tons of sideritic ore, about 2,7 millions are proved reserves and 1,8 million probable reserves.
One can therefore conclude that not only the quality of the ore but reserves as well, the guadramil deposit has a definitive economic value, thought it cannot be the future national siderurgical basis.

5. Relatório do Serviço de Fomento Mineiro do Ano de 1955.
J. L. Guimarães dos Santos (77 pages)


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