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MINERALOGIA, MORFOLOGIA E CRISTALOQUÍMICA DA MONAZITA DE CATALÃO I (GO, BRASIL)

2004; Sociedade Brasileira de Geologia; Volume: 34; Issue: 1 Linguagem: Inglês

10.5327/rbg.v34i1.1100

2317-4889

Maria Cristina Motta de Toledo, Sônia Maria Barros de Oliveira, François Fontan, Viviane Carillo Ferrari, Philippe de Parseval,

Geochemistry and Elemental Analysis

The Catalao alkaline carbonatite complex hosts a number of mineral resources including monazite. This mineral is a common accessory phase in two lithological units: carbonatite and silexite. Textural evidence suggest that monazite replaced carbonates in the carbonatite and crystallized simultaneously with quartz in the silexite. Monazite was resistant to the strong laterization that affected the massif, except for the incipient transformation into gorceixite or cerianite. In both carbonatite and silexite, monazite occurs as a complex aggregate of sub-micrometric crystals, showing unusual morphological and chemical characteristics. It contains Ca, Sr, and Ba in the A-site, and shows a certain degree of hydration indicated by ATD and IV data. Structural formulae calculated on the basis of sum of cations=1 show a moderate ionic deficiency in the anionic site. Rietveld reffinement indicated poor crystallinity. Notwithstanding these peculiar characteristics, cell dimensions are similar to those of standard monazite.