info:eu-repo/semantics/article
PEGMATITES IN SOUTHEASTERN BRAZIL
PEGMATITES IN SOUTHEASTERN BRAZIL
Autor
BILAL, ESSAÏD
NEVES, JOSÉ MARQUES CORREIA
FUZIKAWA, KAZUO
HORN, ADOLF HEINRICH
MARCIANO, VITÓRIA RÉGIA PERES DA ROCHA OLIVEIROS
FERNANDES, MARIA LOURDES SOUZA
MOUTTE, JAQUES
MELLO, FERNANDO MACHADO DE
NASRAQUI, MOHAMED
Institución
Resumen
Two pegmatite groups are represented in southeastern Brazil. The first group, resulting from fractional crystallization, is linked to syn-tectonic granites (580 Ma – deformation event D1) and the second one is associated with another partial melting event of the crust which simultaneously produced porphyritic leucogranites [(520-500 Ma)- later deformation event D2 ] and pegmatites themselves. The Fe/Mn ratios of tourmalines, micas and columbite-tantalites decrease continuously from simple pegmatites to gem quality elbaite-rich ones. The Fe/Mn ratio has been used as a qualitative fractionation index which seems to reflect the regional zoning of the first pegmatites group around a hidden granite body. The Fe/Mn ratio values correlate negatively with Na and Li contents in tourmalines and mica. The REE, Nb, Co and Zn contents in tourmalines, micas, and columbite-tantalites are controlled by their mineral assemblages. Two pegmatite groups are represented in southeastern Brazil. The first group, resulting from fractional crystallization, is linked to syn-tectonic granites (580 Ma – deformation event D1) and the second one is associated with another partial melting event of the crust which simultaneously produced porphyritic leucogranites [(520-500 Ma)- later deformation event D2 ] and pegmatites themselves. The Fe/Mn ratios of tourmalines, micas and columbite-tantalites decrease continuously from simple pegmatites to gem quality elbaite-rich ones. The Fe/Mn ratio has been used as a qualitative fractionation index which seems to reflect the regional zoning of the first pegmatites group around a hidden granite body. The Fe/Mn ratio values correlate negatively with Na and Li contents in tourmalines and mica. The REE, Nb, Co and Zn contents in tourmalines, micas, and columbite-tantalites are controlled by their mineral assemblages.