Neoproterozoic Taymyr Ophiolitic Belts and Opening of the Paleo-Pacific Ocean

Abstract

The Taymyr Neoproterozoic ophiolites are located within the Precambrian accretionary belt, which occurs between the Siberian continent and the Kara continental block. Petrological-geochemical studies suggest that the formation of ophiolites reflects an ensimatic marginal-sea geodynamic environment. Zircon U-Pb dating and Sm-Nd isotopic study suggest a Neoproterozoic age for the plagiogranite from the Chelyuskin ophiolite belt. We regard the zircon U-Pb age (740 Ma) as the upper age boundary for the formation of the ophiolites and the Sm-Nd model age (850 to 785 Ma) as its lower boundary. Data on Sm-Nd, Rb-Sr, Ar-Ar, and K-Ar isotopic systems in garnet amphibolites from the Stanovoy ophiolite belt allowed us to establish the age interval of their metamorphism, ∼600 Ma, as the time of obduction of ophiolites and the entire accretionary belt onto the Siberian craton margin. Age data on island-arc volcanics and plagiogranites as well as diabase dikes and sills, traced from the Canadian Cordillera through the Yukon and Franklin belts of North America and further through the Alaska-Chukchi block to Taymyr, may be indicative of the opening of the northern Paleo-Pacific at ∼800 Ma.