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Mineral chemistry of cassiterites from Pitinga Province, Amozonian Craton, Brazil.

Authors
Publisher
Zeppelini Editorial
Publication Date
Keywords
  • Amazonian Craton
  • Pitinga Province
  • Mineral Chemistry
  • Cassiterite
Disciplines
  • Chemistry
  • Earth Science
  • Geography

Abstract

Tin mineralization in the Pitinga Province is associated with Paleoproterozoic (1.82 Ga) Madeira and Água Boa plutons. The primary mineralization occurs as (1) disseminated cassiterite in the magmatic albite granite facies of the Madeira pluton; (2) hydrothermal cassiterite, related with greisen and episyenites in the Água Boa pluton. Another type of mineralization is secondary and associated with the lateritic profile developed over the albite granite. The aim of this paper is to discuss the mineralogical and chemical characteristics of these cassiterites and the relationships between them and the style of mineralization. The cassiterites of group (1) show higher FeO, Nb2O5, and Ta2O5. and lower TiO2 contents when compared to those of the other groups. A coupled substitution 3 Sn4+􀃅􀃆 (Nb, Ta)5+ + Fe2+ is dominant and best explain the chemical variation observed in this group. The cassiterites from the group (2) and the laterites have comparatively higher TiO2 contents indicating that the mechanism Sn4+ 􀃅􀃆 Ti4+ is dominant. Thermogravimetric analysis and the non-stoichiometric behavior showed in some plots by the cassiterite of the laterite suggests that the coupled mechanism Sn4+ + O2 􀃅􀃆 Fe3+ + OH" is also effective in that group.

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