A Brasiliano age (500 +/- Ma) for the mina III gold deposit, Crixas Greenstone belt, Central Brazil

K-Ar and 40Ar/39Ar geochronological studies were performed on selected minerals from the Minna III gold deposit, Crixas greenstone belt, state of Goias, central Brazil. They include amphibole and biotite from amphibole schists ; biotite from quartz-chlorite-carbonate-muscovite schists ; chloritoid, muscovite, and paragonite from muscovite schists ; and biotite from biotite-marbles. Analyses yielded ages between 750 and 500 Ma, indicating that the Brasiliano orogenic event affected rocks of the Archean greenstone belt. It is proposed that the gold mineralization, closely related to a post-metamorphic peak hydrothermal alteration and spatially associated with muscovite schists, is 505 +/- 10 Ma, whereas older ages may indicate an excess of argon. (Résumé d'auteur

A Brasiliano age (500 +/- Ma) for the mina III gold deposit, Crixas Greenstone belt, Central Brazil

K-Ar and 40Ar/39Ar geochronological studies were performed on selected minerals from the Minna III gold deposit, Crixas greenstone belt, state of Goias, central Brazil. They include amphibole and biotite from amphibole schists ; biotite from quartz-chlorite-carbonate-muscovite schists ; chloritoid, muscovite, and paragonite from muscovite schists ; and biotite from biotite-marbles. Analyses yielded ages between 750 and 500 Ma, indicating that the Brasiliano orogenic event affected rocks of the Archean greenstone belt. It is proposed that the gold mineralization, closely related to a post-metamorphic peak hydrothermal alteration and spatially associated with muscovite schists, is 505 +/- 10 Ma, whereas older ages may indicate an excess of argon. (Résumé d'auteur