Heavy minerals inbottom sediments from the Caraguatatuba Bay-SP-Brazil

Abstract

The bottom sediments of the Caraguatatuba bay, localized in the coast of São Paulo State, were collected for a qualitative study of the heavy minerals in the sandy fraction between 0,125 and 0,062 mm. The mineralogical study allowed the recognition of three groups of heavy minerals: group I – opaque minerals, with magnetite, ilmenite and pyrite; group II – transparent minerals, with amphibole, pyroxene, epidote, biotite, muscovite, zircon, tourmaline, titanite, rutile and apatite; and group III – carbonates, represented by bioclasts and aragonite needles. The source areas of these heavy detritic minerals are related with rocks of the coastal complex, of syntectonic granites and of the alkaline rocks from São Sebastião island. The average content of heavy detritic minerals in the Caraguatatuba bay is 0,77%. Besides biotite and bioclast material, magnetite and ilmenite, are the most abundant phases with an average percentage of 12,9% in the 0,125/0,062 mm fraction.