The Peralkaline Tin-Mineralizes Madeira Cryolite Albite-Rich Granite of Pitinga, Amazonian Craton, Brazil: Petrography, Mineralogy and Crystallization Processes.

• Autor(a) principal: Costi, Hilton Túlio
• Data de Publicação: 2009
• Outros Autores: Dall'Agnol, Roberto, Pichavant, Michel, Ramo, Osmo Tapani
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional do MPEG
• Texto Completo: http://repositorio.museu-goeldi.br/handle/mgoeldi/99
• topic: Albita-granito; Granito; Estanho; Peralcalinos; Criolita; Granito Madeira; Mina Pitinga; Nióbio; Petrografia; Mineralogia

The 1.818 Ga magmatic, subsolvus, Madeira albite-rich granite of the Pitinga province, exploited at the Pitinga mine, in northern Brazil, crystallized from a F-rich melt, also enriched in Sn, Rb, and HFSE. It is composed of a peralkaline, cryolitebearing core facies and a peraluminous to metaluminous, oxidized, fluorite-bearing border facies, generated by autometasomatic processes after the crystallization of the core facies. A metaluminous to peralkaline hypersolvus granite is comagmatic with the albite-rich granite. Petrographic studies indicate that quartz was the first phase to crystallize, at ~700°C; the quartz – K-feldspar cotectic was attained at around 650°C, and the ternary feldspar solvus and onset of albite crystallization down to the solidus, estimated at around 500°C. Massive cryolite and pegmatitic rocks found in the center of the stock were derived from the residual melt. The albite-rich granite probably originated by crystallization of a dense, F-rich, peralkaline phase derived from a peralkaline to metaluminous parental melt by immiscibility.