Produção Nacional
A COLUMBITIZAÇÃO DO PIROCLORO DO ALBITA GRANITO NA MINA PITINGA (AM): RELAÇÕES COM A MINERALIZAÇÃO DE CRIOLITA
2006; Sociedade Brasileira de Geologia; Volume: 36; Issue: 1 Linguagem: Inglês
10.25249/0375-7536.200636s1124137
ISSN2177-4382
AutoresOrlando Renato Rigon Minuzzi, Artur Cezar Bastos Neto, Vítor Paulo Pereira, LISANDRO NUNES,
Tópico(s)Geological and Geochemical Analysis
ResumoAt the Pitinga mine (Amazonas state) the primary ore is associated with the Madeira granite albite facies that contains a world class Sn deposit and a important Nb, Ta, ETR, Y and F (cryolite) reserves. This study show the relationships among disseminated Nb/Ta ore cryolite (disseminated and massive) around the Cryolite Massive Deposit. The magmatic U-Pb-pyroclore was altereted by a fluid rich in fluorine. ln an initial stage, Pb was lost and U and Nb were enriched resulting in Pb-U and U-pyroclores. This process promote an increasing in site A vacancy and the piroclore structure colapse and result in columbite formation. This mineral mantain the Sn and U geochemical signatures, that are inherited from pyroclore. The Pb impoverishment was followed by Ca, F, Ce and Sn relative enrichment and Fe impoverishment. These behavior change at the transition zone between the nucleus and border albite granite subfacies. It was interpreted as product ofreduction on the fluorine activity, that promote the columbitization. Spatial relationships among pyroclore varieties and columbite distribution and Cryolite Massive Deposit permited verify that the columbitization process was promoted by the cryolite mineralizing fluido Gradients linked to F on this fluid probably explains the geochemical descontinuities in the studied minerais, as well as some differences among the nucleus and border albite granite subfacies. Some implications on Nb/Ta mining and recovering are also discussed.
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