MAPAS PREVISIONAIS: CONCEPÇÃO E SUGESTÃO DE SUA APLICAÇÃO NA CARTOGRAFIA GEOLÓGICA BÁSICA NO BRASIL

HARTMUT BEURLEN

Resumo


Previsional maps according to the French conception of Nicolini (1970) should be the result of mapping and graphical representation of geologic features with confirmed importance for prospecting a certain mineral resource. In contrast, metallogenetic maps represent geologlcal themes that are supposed to be responsible for the genesis of a mineralization according to subjective and, thus, ephemeral models. In a true previsional map all possible metallotects should be tested as objectively as possible - may be statistically - according to the congruence degree with the known mineralization in(a) test area(s). According to this degree of congruence a rank of priority has to be established for the different metallotects. The cartographic representation of the selected features may be realized by conventions regardless of the scale of the final map. Data unusual in geologic maps, such as isopachs, distances to special rocks, structures, geomorphological límits etc, will also be represented when their importance is confirmed. The final scale must be the result or the size of the metallotects to be represented, and not preestablished. All features must be systematically mapped in the whole area independently of the scale of graphical representation. The final map has to indicate an order of priority for targets to be prospected . This order ís given by th e superposition of a greater number of confirmed metallotects. It is proposed that a similar procedure should be adopted in the usual systematic geological survey programa. Thus, previsional maps could be obtained as a low cost by-product.

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