CARACTERIZAÇÃO E EVOLUÇÃO DAS MICAS DO GRANITO ESTANÍFERO DA PEDRA BRANCA (GOIÁS) EM RELAÇÃO AOS PROCESSOS MINERALIZADORES TARDI/PÓS-MAGMÁTICOS

NILSON FRANCISQUINI BOTELHO

Resumo


The Pedra Branca Granite Massif is one of the granitic bodies wíth major metallogenetíc potential in the Goiás Tin Province. The study of micas brought much information about the late magmatic alterations responsible for the most important mineral concentrations in the Serra da Pedra Branca area. Biotite of the primitive porphyritic granite is a zincian fluorsiderophylite similar to biotites from many tin granites elsewhere. Two types of secondary biotite were identified; the late one, classified as protolithionite, is rich in Si, Fe3+, Sn, Li and F. This type occurs in mineralized greisen and greisenized granite, associated with quartz, topaz and fluorite. Muscovites are af secondary origin, related to albitization and greisenization events. The three identified types are enriched in Sn, F, Rb and Li, even though lithium values do not have the same significance as in muscovites from known greisens in many occurrences all over the world. It is suggested that petrographic and petrochemical characterization of mícas from a granite massif may be used as a guide to indicate the most favourable tin granites.

Texto completo:

PDF

Apontamentos

  • Não há apontamentos.