Age and composition of basement beneath the De Long archipelago, Arctic Russia, based on zircon U–Pb geochronology and O–Hf isotopic systematics from crustal xenoliths in basalts of Zhokhov Island

Abstract

U–Pb ages, in conjunction with oxygen isotope and hafnium isotope geochemistry of zircons from granitic and siliciclastic crustal xenoliths from Cenozoic alkali basalts on Zhokhov Island (De Long Archipelago, Russian Arctic), provide new insights about the island’s subsurface geology. Zircons from granitic gneiss xenoliths yield 206Pb/238U ages ranging from 600 to 660 Ma, similar to protolith ages of granite intrusions and orthogneisses in Protouralian–Timanian magmatic basement of the northern Urals as well as to rocks that form the basement of Arctic Chukotka and Wrangel Island, thus suggesting continuity between these three regions. Depleted mantle-like Hf and O isotopic signatures in the dated zircons suggest juvenile crust that originally formed in the Neoproterozoic and was later reworked during the Paleozoic and Mesozoic. Sandstone xenoliths contain detrital zircon (DZ) populations that establish their depositional age as younger than Permian and reveal similarities to DZ populations of Permian and Triassic strata of Taimyr and Chukotka.