SILURIAN GRANITOID MAGMATISM OF THE RASSOKHA TERRANE (NORTH-EAST RUSSIA)
U–Pb dating of zircons from granitoids located within the Rassokha terrane showed the Silurian age of their formation. Younger ages from one of the samples are related to the radiogenic lead loss during secondary alteration of rocks. According to REE distribution as well as to well-defined positive anomalies of K, Pb and negative anomalies of Ba, Sr, Nb, Ta, Ti they are comparable with rocks of suprasubduction environments. With reference to the dating of intrusions from adjacent areas, Silurian granitoid magmatism of the Rassokha terrane supports the existence of back-arc basin and a long island arc in the Ordovician-Silurian time.