Data??o U-Pb em zirc?o por SHRIMP de granitos Neoproterozoicos da por??o oriental do Domínio S?o Roque, Faixa Ribeira

摘要

Four granitic plutons from the easternmost portion of the S?o Roque Domain (SRD) were dated by U-Pb zircon SHRIMP;?the results indicate that the peak of granitic magmatism was concentrated in a short interval (606–589 Ma), the same as?in the central portion of the SRD. The two porphyritic biotite granites (Morro Azul and Imbiru?u) yield the oldest ages?(respectively, 601.0 ± 4.9 Ma and 606.3 ± 4.8 Ma) and have inherited zircons with similar ages (~2.1–2.0 Ga), but are not?comagmatic. The Morro Azul granite has geochemical signature similar to other high-K calc-alkaline (HKCA) granites?from the SRD, while the Imbiru?u granite has much higher Sr/Zr and other chemical features that demand different sources.?Other two dated samples are very different from each other and from the HKCA granites. The age of the Morro do P?o?tonalite (589.1 ± 5.5 Ma) indicates that, in spite of its more deformed character, it is younger; a similar value, although with?large uncertainty, is shown by the Serra dos índios peraluminous leucogranite (593 ± 12 Ma). Our analytic data combined?with field relationships suggest that soon after the main episode of HKCA magmatism, the SRD witnessed the emplacement?of granites of varied composition forming small bodies that recorded deformation associated with transcurrent tectonics.