Descrição

Artigos

1. A Estação Pré-histórica de Vale de Carro (Albufeira).
O. da Veiga Ferreira ; L. de Albuquerque e Castro (8 páginas)

2. Algumas Formações Montmoriloníticas Portuguesas.
A. Cândido de Medeiros (5 páginas)
Resumo: Por não ser possível, devido ao estado de guerra, obter as bentonites necessárias ao consumo da indústria nacional, algumas empresas (entre elas: Indústria de Produtos Químicos de Moreira da Maia-Porto) solicitaram do Serviço de Fomento Mineiro informações relativas à existência, em Portugal, do referido produto ou de qualquer outro que o substituisse.Dentro deste espírito, realizaram-se visitas de reconhecimento e estudo a várias formações montmoriloníticas do Norte do País para se ajuízar das suas possibilidades de emprego industrial.

3. Bibliografia Mineira.
N. A. Múrias de Queirós
Resumo: O autor começa a sua nota por analisar o problema do cálculo dos revestimentos de poços em terrenos muito aquíferos. Cita algumas fórmulas utilizadas no cálculo da espessura do revestimento dos poços circulares e deduz, em seguida, uma nova fórmula, que dando maiores valores para a espessura de revestimento do que a dos tratadistas, se afigura mais vantajosa perante o estudo das tensões a que fica sujeito o material.Verificando que as discordâncias entre a fórmula deduzida e as clássicas passam a ter maior valor à medida que aumenta a pressão ou baixa a carga de segurança, vê-se da vantagem da aplicação da fórmula do autor, e da prudência a ter no uso das fórmulas congagradas. É em seguida apresentada pelo autor uma nova fórmula para a determinação da espessura dos revestimentos no caso dos terrenos resistentes e pouco aquíferos. São, a propósito, feitas judiciosas considerações de interesse prático.
Ainda é apresentada, nesta nota, uma fórmula para o cálculo das pressões dos parâmetros dos poços, de modo a calcular-se a secção das peças que constituem os revestimentos em quadros de madeira dum poço de secção rectangular. O autor, neste seu trabalho, lembra, por fim, que a solução teórica perfeita exigiria o conhecimento exacto das densidades médias dos terrenos e coeficientes de Poisson.

4. Gisements de Minerais de Fer du Sud du Portugal.
João Martins da Silva (12 páginas)
Resumo: In South Portugal there are the following kinds of iron deposits:

a) Deposits formed by concentration in magmas. Irregular masses of magnetite included in gabbros. The ore structure is similar to that of the adjoining rock. Minerals of metasomatic replacement are absent.

b) Pyrometasomatic deposits not related to contacts. The orebodies are lenticular masses of magnetite with pyrite that follow the stratification of adjoining rocks. These iron ores are in an Archaean series cut by eruptive rocks. They occur in crystalline limestones or at the contact of these with metamorphic schists.

c) Pyrometasomatic deposits. The iron ore occurs at the contact of crystalline limestone with diorite and is accompained by «skarn».

d) Veined deposits. The ore is hematite and limonite with manganese oxides. The walls are formed by quartz and barite, which are also the predominating gangue minerals.

e) Sedimentary deposits. Hematite ores with quartz occuring in Archaen-Precambrian rocks.

5. Montmorillonite dans des Pegmatites Granitiques et le Problème de la Montmorillonitisation.
D. J. Rosas da Silva ; J. M. Cotelo Neiva (5 páginas)
Resumo: Montmorillonite occurs in Portuguese granitic pegmatites partially replacing the orthoclase and microcline. Such a replacement would have ocurred through alkaline and magnesian hydrothermal solutions varying from 200° to 300° C. Under these conditions the feldspar would principally lose its alkalies and a part of silica, undergoing the inclusion of magnesium and water.

6. Principaux Gisements de Minerais de Plomb et de Zinc du Portugal.
J. L. Guimarães dos Santos (13 páginas)
Resumo: Though the earliest worked ore deposit, the concession of which was granted in 1836, was of lead, there are few lead or zinc deposits with real economic value. Most of the ore deposits are of the blende-galena-pyrite or blende-galena and calamine types. Sometimes the mineral association are more complex, with bismuth, nickel and cobalt ores. Galena appears as accessory ore in some auriferous and uraniferous ore deposits associated with torbernite and antunite. The deposits being of vein origin present generally a lenticular arrangement, the mineralization being in columns or zones and the useful ore being distributed in small lodes, concretions or spots of mineral concentrations. Extensive mineralised zones are rare. The main ore deposits are situated in the northern part of the country, north of the river Tagus. The production of galena reached its highest values between 1890 and 1900, and has been very limited during the last 15 years. The Vouga and Caima mining areas, situated in the centre of the country, are those which contributed most to the Portuguese production, but they are now facing the difficulties met by explorations having a long history. The production of blende was always very small and nowadays practically does not exist. As studies on most ore deposits are incomplete, limited or superficial, it is not possible to establish an accurate estimate of the reserves of lead and zinc. For some years the Portuguese State carried out a prospection program with a view to estimating the richness of the sub-sole, but, for the time being, it is not possible to supply estimates. It is foreseen that Portuguese reserves of lead and zinc will be very short and insufficient for the needs of the country.

7. Serpentines et Serpentinisation.
J. M. Cotelo Neiva (17 páginas)
Resumo: The serpentines have generally a mesh texture and rarely fibrous lamellar (felted), serpophitic, spherulitic and semi-spherulitic texture. Among the essential serpentinous minerals it has been possible to classify the following types:

a) serpophitic;

b) bastitic;

c) chrysotilic;

d) antigoritic;

e) chrysotilic-bastitic;

f) antigoritic-bastitic;

g) chrysotilic-antigoritic;

h) chrysotilic-serpophitic;

i) antigoritic-serpophitic;

j) chrysotilic-serpophitic-bastitic;

k) chrysotilic-serpophitic-antigoritic;

l) chrysotilic-antigoritic-bastitic;

m) serpophitic-antigoritic-bastitic;

n) chrysotilic-antigoritic-serpophitic-bastitic;

o) chloritic.

The serpentines have, as acessory minerals, magnetite, and other ferriferous pigments and, accidentaly, chromite, picotite, pleonaste, talc, clinochlore, tremolite-actinolite, magnesite and calcite. By their chemistry, the serpentines are ortho-metamorphic rocks as a result of metamorphism from rocks of calc-alkaline chemistry of the family of the peridotites; of the serpentines analysed some have peridotitic and others koswitic chemistry.

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