Caracterização e distribuição dos minerais pesados ao longo da plataforma continental do Espírito Santo

Abstract

The heavy minerals have a density greater than 2,8 g/cm3 , upper to that of quartz (2,65 g/ cm3 ) and appear as accessory minerals in sedimentary, igneous and metamorphic rocks. The heavy minerals were used as a tool to better understand the past and present sedimentary processes of the Continental Shelf of Espírito Santo (CSES). The study area was subdivided into 3 sectores: Paleovalley Shelf, Doceriver Shelf and Abrolhos Shelf. The sediments found in the CSES are siliciclastic, biodetritic and mixed distributed in a peculiar manner respecting the different sedimentological characteristics governed by accommodation and supply regimes. Fifteen different species of heavy minerals were identified in the CSES: Ilmenite, limonite, sillimanite, zircon, tourmaline, epidote, monazite, hematite, magnetite, grenade, staourolite, rutile, titanite, andaluzita and kyanite. The deposits of heavy minerals with higher concentrations are found in the Doce river Shelf and Abrolhos Shelf, presenting values of maximum content of 3,6%. ZTR index values (zircon, tourmaline and rutile) associated with the interpretation of bathymetric profiles and geological knowledge on CSES have led us to believe that the most expressive heavy mineral deposits are composed of relict sediments possibly from past river transport associated with the relative lowering of sea level in the Late Quaternary.