Protolith ages of eclogites, Marun-Keu Complex, Polar Urals, Russia: implications for the pre- and early Uralian evolution of the northeastern European continental margin

Abstract

Abstract Single zircon U-Pb dating by ion microprobe and Pb-evaporation techniques, combined with Sr-Nd isotopic and geochemical data, constrain the pre- and early Uralian evolution of the Marun-Keu eclogite-facies metamorphic complex. Polar Urals, Russia. The complex is interpreted as a part of the Early Palaeozoic East European passive margin, subducted, metamorphosed and exhumed during Uralian arc-continent collision. In the Marun-Keu complex, a variety of meta-igneous and metasedimentary rocks documents different evolutionary stages of the northeastern margin of Baltica. Both the oldest, polystage detrital zircon population, which is 570 to 700 Ma in age, and the dominant zircon population in an island arc-type magmatic suite ( c. 550 Ma) are related to the Neoproterozoic Timanian orogeny, which resulted in continental growth of northeastern Europe by accretion of juvenile oceanic and island arc material. A distinct magmatic event at c. 490 Ma is documented in zircons from metagranites, and is interpreted as evidence for incipient post-Timanian rifting which finally led to formation of both the Proto-Uralian ocean and the Early Palaeozoic East European passive margin. A convergent setting was re-established in Silurian times, culminating in Uralian arc-continent collision by east-dipping subduction of the East European passive margin. Metamorphic zircon ages reflect the collision event at 360 to 355 Ma.