OLD GEOPHYSICAL DATA APPLIED TO MODERN GEOLOGICAL MAPPING PROBLEMS: A CASE-STUDY IN THE SERIDÓ BELT, NE BRAZIL

ELTON LUIZ DANTAS, ADALENE MOREIRA SILVA, TATI ALMEIDA, ROBERTO ALEXANDRE VITÓRIA DE MORAES

Resumo


The Seridó belt, northeast Brazil, is a Brasiliano-Pan-African collisional orogen formed between the West African, São Francisco and Amazon cratons during the west Gondwana assemblage. This area is an excellent example for illustrating the usefulness of gamma-ray spectrometric data to support modern geological mapping in semi-arid terranes. Analyses of K, Th and U channels images, displayed as composite themes, correlate well with the main regional framework of the Seridó Belt. Several distinct mapped units are easily distinguishable in the gamma-ray spectrometric data, as the Paleoproterozoic basement rocks and the supracrustal metasedimentary sequences of the Neoproterozoic Seridó Group. Also, the granitic plutons and the Phanerozoic cover show different geophysical signatures. Definition of contacts among units, faults, folds and shapes of granitic intrusions are considerably enhanced by the airborne gammaray spectrometry data. The results here presented show that there is a strong relationship among geochemical, isotopic and geophysical signatures of different crustal blocks recognized in the region. This kind of approach seems fundamental for investigating regional crustal evolution in overly complex deformed Precambrian areas. It also can be of some help to better define the boundaries of the different lithostratigraphic units that could appear in similar orogenic belts within the Brazilian Shield.


Palavras-chave


Seridó Belt; Modern geological mapping; Airborne gamma-ray spectrometry data; Semi-arid terranes.

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