Isotopic signatures of paleoproterozoic granitoids of the gavião block and implications for the evolution of the São Francisco Craton, Bahia, Brazil

Abstract

Intense granitic plutonism of peraluminous and metaluminous calc-alkaline affinity took place in the northern sector of the São Francisco Craton, during the Paleoproterozoic. Rb-Sr and 207Pb/206Pb(zircon) radiometric data for the granitoids yield crystallization ages at ca. 2.0 Ga. The calculated 87Sr/86Sr initial ratios (up to 0.727), TDM model ages (between 2.6 and 3.5 Ga) and the range in the eNd(t) values (-5.8 to -13.4) are all compatible with participation of variable proportions of Archean crust material in the magma genesis of such plutons. Technically, these granites originated due to the Transamazonian collisional orogeny, which developed within large terranes of the Craton along the edge of the Archean Gavião Block.