The "Upper Basalts" of the East Chukotka Segment of Okhotsk–Chukotka Belt: the Along Strike Migration of Volcanic Activity or the Overprint by Later Magmatic Event?

New U–Pb and 40Ar/39Ar isotopic dates on volcanic rocks of the East Chukotka segment of the Okhotsk–Chukotka Belt correspond to 76–71 Ma span, which is partially beyond the conventional lifetime of this volcanic province. This could result from the migration of magmatic loci along the strike of the volcanic belt, and/or from the overprint by a younger magmatic event. [ABSTRACT FROM AUTHOR]