New Data on the Age of Igneous Complexes of the Alazey–Oloy Foldbelt (Western Chukotka)

Abstract

New data on the age of the intrusive and subvolcanic rocks of the Oloy zone in Chukotka hosting commercially important Au–polymetallic and Cu–porphyry ore occurrences of the Burgakhchan area are reported. The age of the intrusive rocks of the Nichan and Vukney massifs, as well as the volcanic rocks of the Zybkin Formation in the Nenkan and Vukmaam structural–facies zones of Chukotka is determined reliably for the first time. U–Pb SHRIMP dating of zircons from three monzodiorite samples from the Nichan massif and three samples from the Vukney massif related to the Ekdygkych Complex provides evidence for their Berriasian–Valanginian age with mid-weighted values from 143 to 139 ± 2 Ma. The ages obtained correlate with the age of the porphyric diorite and monzonite of the Ekdygkych massif on the Peschanka deposit and indicate the high commercial significance of the studied intrusive complexes. The ore-bearing rocks intrude the volcanogenic–sedimentary rocks of the Zybkin Formation with a U–Pb zircon age of 146.5 ± 3 Ma.