ESTUDO PETROGRÁFICO DAS ROCHAS ÍGNEAS ALCALINAS DA REGIÃO DE LAGOA FORMOSA, MG

HILDOR JOSÉ SEER, LÚCIA CASTANHEIRA DE MORAES

Resumo


The first results of a petrographic study about the alkaline rocks from Lagoa Formosa region, Minas Gerais, Brazil, are presented. The rocks belong to the Cretaceous Mata da Corda Formation of the São Francisco Basin comprising volcanic breccias, lapillites, tuffs, cinerites, lava flows, volcanic pipes, and dykes. The related petrographic terms are mela-leucitites and minor sienites, alkalipyroxenite, and basalt, Generally, the rocks are porphyritic, mafic with olivine, phologopite and pyroxene phenocrysts in a pyroxene, leucite, phlogopite afanitic matrix.


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