In:
Sciences Géologiques. Bulletin, PERSEE Program, Vol. 41, No. 1 ( 1988), p. 5-36
Abstract:
In Brazil, the same processes responsiblefor the formation of the thick lateritic mantle, which covers nearly 65 % of its territory , arc also responsible for metal accumulation which forms, under special condition, the lateritic ore deposits. In the origin of those accumulation, the parent rock composition and/or the convergence of the biological and morphoclimatic factors play a fundamental role. Considering this point of view, different lateritic ore deposits are discussed in this paper. Thus, the weathering of the Banded Iron Formations (from Archean to Upper Proterozoic) gave origin to some of the biggest iron deposits in the world at Carajas (Para), Quadrilatero Ferrifero (Minas Gérais) and Urucum (Mato Grosso). The products of the weathering of various rocks constituted very important bauxite deposits : Cretaceous alkaline massifs in the Southeast Brazil (Minas Gérais, Sao Paulo, Rio de Janeiro, Santa Catarina) ; Precambrian metamorphic or volcanic rocks in the Central-East Brazil (Quadrilatero Ferrifero, Atlantic coastal ridge) ; and Tertiary continental sediments in the Amazonian Basin (Trombetas, Paragominas, ...). The lateritic alteration concentrated the manganese from rocks that have been previously enriched in this element by volcanic-sedimentary processes (Amazônia, Minas Gérais). Finally, nicke-liferous latentes were accumulated by the weathering of ultramafic massifs scattered all over the country, concentrated mainly in Central Brazil (Barro Alto and Niquelandia, Goias), but also occurring in the more humid regions (Atlantic Coast and Amazônia). All this lateritic evolution of very specific bed rocks occurred essentially in the Tertiary during periods of tectonic stability which are related with extense erosional surfaces. The influence of lithologie, climatic and morphotectonic factors on the mechanism of formation of lateritic deposits is discussed.
Type of Medium:
Online Resource
ISSN:
0302-2692
DOI:
10.3406/sgeol.1988.1779
Language:
French
Publisher:
PERSEE Program
Publication Date:
1988
detail.hit.zdb_id:
192632-9
SSG:
13
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