GEOCHEMISTRY AND AGE OF ZIRCON FROM KHAPCHAN ACCRETIONAL OLISTOSTROM OF ANABAR SHIELD

Chaotic breccias in carbonate rocks of the Paleoproterozoic Khapchan series of the Anabar Shield were characterized for the first time. Breccias belong to the flysch-carbonate subtype of accretionary olistostrome and confirm the existence of a subduction zone in the Paleoproterozoic in the east of the Anabar Shield. The olistostrome was formed in connection with underwater thrusts during the destruction of an accretionary uplift composed of weakly lithified and loose sedimentary material. The Sm-Nd isotope system of olistostrome rocks indicates a Paleoproterozoic age (TNd(DM2) = 2.34-2.42 Ga) and a juvenile (εNd(T) = 0.6-1.5) proximal nature of the rock source. U-Pb dating of zircon from detrital material and olistostrome matrix constrains the lower temporal boundary of the accretionary stage in the Khapchan Belt. Based on detrital zircon from the carbonate matrix of the olistostrome, the age of accretion is no older than 2009 ± 11 Ma. Granulite metamorphism with an age of 1898 ± 5 Ma is caused by collision events that followed accretion.