Long-lived proterozoic chemical heterogeneity of the sub-continental lithospheric mantle beneath northeastern Brazil

Mechanisms suggested for lithospheric enrichment include the influx of metasomatizing agents derived from subducting slabs (Jahn et al., 1999, Peccerillo, 1999) or infiltration by asthenospheric melts during periods of regional extension (e.g., Beraton, 1999). These processes redistribute incompatible trace elements and lead to anomalous enrichment, a diagnostic feature of mantle metasomatism (Roden and Murthy, 1985). Enrichment in light rare earth elements and accompanying fractionation between Sm and Nd occur as a consequence of such processes, causing the decrease in the Sm/Nd ratio of the modified mantle reservoir. This behavior makes Sm-Nd model ages useful tool for constraining the timing of chemical changes in the mantle. This paper reports Sr-Nd isotope features of magmas generated from the sub-continental lithospheric mantle (SCLM) beneath the Borborema Province, northeastern Brazil. For this study, we focus on regional mantle-derived magmatism ranging in age from late-Neoproterozoic to Mesozoic and Cenozoic in the Rio Grande do Norte Domain (RGND), in the northernmost portion of the Borborema Province where the resulting mafic rocks are well exposed. The isotope data allow us to establish correlation between the timing of chemical modification processes in the mantle and the chronology of tectonic events previously defined for the Borborema Province (au)