Mineralogic and petrographic variations in the central portion of the Madeira albite granite, Pitinga, AM
Abstract
The Pitinga albite granite is a porphyritic facies of the Paleoproterozoic Madeira Granite (~1.83Ga) containing major massif and disseminated cryolite in its core. The phenocrysts, mainly quartz but also potassic feldspar, mica e amphibole associated with zircon, cryolite, polylithionite, pyrochlore, cassiterite and magnetite are corroded by an albitic matrix composed by albite, potassic feldspar, quartz, cassiterite, cryolite, opaque minerals and secondary fluorite. The mineralogical and petrographic variations, observed in the granite core, suggests that saline, water-rich fluids exsolved from the same body of magma allowed the occurrence of oxidation reactions and cryolitization, argillization and silicification processes, which are responsible for corrosion and replacement of primary magmatic minerals in a late stage of its cooling history.
Key words: albite-granite, cryolite, Pitinga,Madeira Granite, Proterozoic.Downloads
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