ABSTRACT
The Seridó fold belt is the host to abundant pegmatites mined for columbite-tantalite, beryl and gem quality tourmaline. The δ18O values of quartz and muscovite from the pegmatites reveal oxygen isotopic reequilibration at low temperatures and/or external contamination. Six U-Pb ages of columbite fall between 509.5 ± 2.9 and 514.9 ± 1.1 Ma. Monazite from peraluminous granite, genetically related to pegmatites yields an age of 535 ± 4.1 Ma. The latter and the heterogeneous pegmatites are interpreted as two distinct and successive magmatic events from a common, deep reservoir, using the same structures during their crustal ascent.
