Silurian Granitoid Magmatism of the Rassokha Terrane (North-East Russia)

U–Pb dating of zircons from granitoids located within the Rassokha terrane show a Silurian age of their formation. Younger dates from one of the samples are related to radiogenic lead loss during secondary alteration of the rocks. Based on REE distributions as well as well-defined positive anomalies of K and Pb and negative anomalies of Ba, Sr, Nb, Ta, and Ti, the granitoids are comparable to rocks from supra-subduction environments. Combined with intrusive ages from adjacent areas, Silurian granitoid magmatism of the Rassokha terrane supports the existence of a back-arc basin and a long island arc in Ordovician-Silurian time.