Recursos Minerais das Bacias Sedimentares. Exemplos brasileiros

Resumo

The matter ts of a great amplitude, so the author intended to put it into the rational reality showing and explaining the geological data as the result of perforations and surface searches.

            On this purpose, he studied the following mineral resources.

            Limestones - The are found in United States in the sedimentary sequences of all geological periods: they are observed in Brazil in Paleozoic and cretaceous basin (Amazonas carboniferous basin and Rio Grande do Norte, Pernambuco and Sergipe cretaceous basin, occurring on Reconcavo Baiano in isolated massive beds).

            They are formed by calcium carbonate and when the are burnt they changed into lime; they are used in civil construction and in different industries; the essential raw-material in the cement fabrication and iron industry.

            Dolamite - It is common n sedimentary deposits, and it has been found in the inferior cretaceous formation of Sergipe.

            By the granules texture and resistance to the di1ute acid chloride in can be used as the substitute of magnesite in the manufacturing of refactury bricks.

            Anhydrite and gypsum - They occur on sedimentary formations of all world making

considerable thick beds. There are Anhydrite and gypsum beds in Brazil in Amazonas carboniferous evaporates Maranhão-Piauí sedimentary basin and in cretaceous border of Ceará Pernambuco and Piauí States. '

            Economical exploiting of gypsum deposits are found in siluriano North New York, and Kansas, Texas, Oklahoma and New Mexico Permian. Tertiary deposits are also notable in Paris basin.

            Anhydrite has sometimes the same color and gypsum texture, but it can be noticed its difference by the greater hardness and specific weight. While Anhydrite has no commercial value gypsum is one of the most important no metallic mineral. When it is pulverized it can be employed as fertilizer to improve soils pH; it becomes plaster when it is burnt and prepared.

            Barite - Barium sulfate is formed in Limestone, it has been found in different places of our territory: São Paulo, Minas Gerais, Paraíba and Amazonas, but the most important deposit is situated in Camamu bay. lt is also found in German and United States where the alluvial deposits are the most important.

            Due its high density it is chemically inet, it is used in ink, rubber and paper industries, etc.

            Distom - Distoms thick beds can be found in Califórnia tertiary territories. There are deposits in Pernambuco and Ceará coasts in plain exploitation.

            It is used as polisher agent, to isolate and to philter liquids and for some cement misture.

            Pyrite - Iron sulphuret is found in clay sediments and can be noticed in South Brazil coast in profusion.

            Probably it is the only brim-stone deposit to make sulphuret acid we have; it is an essential industry product.

            After emphasizing potassium salts as a "silvita" and carnelian are more soluble than sodium chloride (halite). He explains they are vital to modern agriculture for improvement of soil; they allow the development of cultivation by quick assimilation.

            He refers yet to another salt deposits in Brazilian sedimentary basins - the salt water  in deep reservatories found in petroleum perforations; one of the biggest occurrence of this water was registered in Alagoas but it is necessary the continuous examination of its salt content in order to make its economical valuation.

            Coal - At first the author gives the occurrence areas for three kinds of coal (anthracite, betuminoses and lignite coal), going after to the brazilian coal that occurs on Rio Grande do Sul, Santa Catarina, Paraná and São Paulo States. He looks over the property of each one and gives the distribution of deposits, he passes to Piauí coal and refers to Prof. Kegel analysis done a t 1955.

            He thinks about the possibility of coal in Amazonian basin and remembers that the natural conditions for its formation are numerous.

He looks at the different coal employment stating that the greatest port of our production is in the electric-therms factory although the concurrence of liquids combustible; he refers to bituminous coal as raw-material in cialbetar fabrication and possible "German" occurrence on south Brazil coals that perhaps will be one of the most valuable sub-product.

            The author considers that as the coal has been the chief energy source, only put a side nowadays by petroleum, however its enormous reserves in the world will make it to perform again an important place near thermonuclear energy which needs we go to a search way on purpose to find out new reserves. .

            Oil shale - Remembering that the distinction of extraction problem between shale and petroleum oil it is its searching. The author goes on giving the United Sates prmcipal reserves an-d its evaluation. He shows too the Brazil case where there is a sedimentary belt convening from São Paulo to Rio Grande do Sul where the problem is almost solved and it commercial one is being considered carefully; he examines this shale potential .he. tells that perhaps it will be possible to get from the oil that has been taken out the principal sulfur sources for our industries.

            He refers also to the experiences made in Paraíba valley and to the horizon that appears in Alagoas, Maranhão and South Camamu.

            Petroleum - The author states that petroleum is found in almost all world sedimentary basins, he looks at ali Venezuela and United States reserves going after to Brazil where he shows three basins: the South, Maranhão, Piauí and Amazonas whose petroleum areas it is calculated about 3. 000.000 km". He refers yet two important cretaceous basins: Alagoas, Sergipe and Recôncavo, this one as the only petroleum productive region in Brazil that we think is promising. Looking at the new discoveries in this region the author says that they can give big reserves.

            He explains about Nova Olinda perfurations trying to show the geological history of paleozoic and cretaceous basin, noticing us that each one of them has a peculiar technical aspect.

            He finishes concluding that national petroleum with present index of productivity and existent reserves is the most important mineral richness in Brazil.