U-PB ZIRCON AGES FROM THE ESKOLABREEN FORMATION, SOUTHERN NY FRIESLAND, SVALBARD

The Eskolabreen Formation is the lowermost unit within the tectonostra tigraphic pile of the Caledonian Hecla Hock succession of Ny Friesland , Svalbard, and is exposed in the core of the Atomfjella Antiform. It is composed of strongly deformed and banded migmatitic gneisses and am phibolites, and intercalated granitic geneisses. U-Pb dating of prisma tic zircons from a band of muscovite-biotite gneiss yields a poorly de fined upper intercept age of ca. 1770 Ma. Zircons From two nearby samp les of granitic gneiss yield a pooled upper intercept age of 1766+/-10 Ma, interpreted to date the intrusion of the granite. A lower interce pt age for these zircons at 404+/-8 Ma, and a similar U-Pb titanite ag e, record the age of Caledonian metamorphism in Ny Friesland. The resu lts agree with U-Pb zircon and titanite ages recorded from the overlyi ng Bangenhuk granitoids, and emphasize the importance of the ca. 1.7-1 .8 Ga tectonothermal event within the intercalated basement units of t he Ny Friesland Caledonides.