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BIBTEX RIS

Altération hydrothermale des monazites-(Ce) des pegmatites du district de Santa Maria de Itabira (Minas Gerais, Brésil)

1998; Volume: 326; Issue: 10 Linguagem: Inglês

10.1016/s1251-8050(98)80180-8

ISSN

1778-4107

Autores

Essaïd Bilal, Vitória Régia Péres da Rocha Oliveiros Marciano, José Marques Correia Neves, Kazuo Fuzikawa, B. F. Riffel, Hermínio Arias Nalini Júnior, Maria Lourdes Souza Fernandes, Mohamed Nasraoui,

Tópico(s)

Geochemistry and Elemental Analysis

Resumo

Monazite-(Ce) is found in granitic pegmatites in the Santa Maria de Itabira pegmatite district (Minas Gerais, Brazil). During the magmatic stage, monazite-(Ce) seems to have had higher contents of cheralite and huttonite in the solid solution. The Th content in primary monazite-(Ce) is high and characteristic for each pegmatite body. During the late stage (albitization), the mean LREE content in the altered zone is slightly higher and Th content is very low. The accessory mineral assemblages changed; huttonite and cheralite crystallize together with Th-poor and La-rich monazite-(Ce) at the border of altered crystals. Nd/Sm and U/Pb ratios are also changed during the hydrothermal stage. Les monazites-(Ce) ont été collectées dans cinq corps pegmatitiques du district de Santa Maria de Itabira (Minas Gerais, Brésil). Les monazites-(Ce) primaires sont riches en thorium et présentent en solution solide de la chéralite et de la huttonite. Une albitisation tardive affecte les pegmatites ; durant ce stade hydrothermal, les monazites-(Ce) s'enrichissent en terres rares légères et s'appauvrissent en thorium. Huttonite et chéralite cristallisent dans les microfissures des monazites-(Ce). Les rapports Sm/Nd et U/Pb varient également au cours de l'altération hydrothermale.

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