The Dzela complex, Polar Urals, Russia: a Neoproterozoic island arc
The Neoproterozoic Dzela complex in the southern part of the Polar Ural Mountains occurs within the Uralian fault zone. It represents residual oceanic lithospheric mantle, partial melt derived from it, and seafloor basalts. In low strain domains, a depleted mantle residue of ultramafic rocks (pyroxenite, lherzolite and dunite) and mafic rocks (gabbro, gabbro-norite and quartz gabbronorite) are preserved. Distinctive negative europium anomalies in the ultramafic rocks (and their metamorphosed equivalents) indicate their residual nature after basaltic melt extraction. Gabbroic rocks (and their metamorphosed equivalents) have elevated rare earth element (REE) concentrations, but similar overall REE patterns as the ultramafic rocks that host them, suggesting that the ultramafic rocks are the source of the gabbroic melts.
Blueschist- and greenschist-facies metabasalts overlie the ultramafic and mafic rocks. Two groups of metabasalts are defined. One has NMORB-like REE patterns, but is uniformly more depleted than NMORB, and the other has slightly enriched (relative to NMORB) LREE/HREE patterns. The latter has high field-strength elements (HFSE) concentrations consistent with formation in an intraoceanic subduction zone setting.
Dzela mafic rocks have been dated for the first time to 578 ± 8 Ma (2σ) (U-Pb zircon from quartz-bearing gabbro-norite), defining a Neoproterozoic crystallization age. The complex was probably accreted to the NE margin of Baltica (sensu lato) during the Timanian Orogeny. Locally reset U-Pb zircon ages of about 350 Ma probably record Uralian orogenesis and recrystallization associated with high-pressure/low-temperature metamorphism. The Dzela complex provides further evidence that ocean-continent collision was the driving mechanism for Timanian Orogeny.
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The Neoproterozoic Timanide Orogen of Eastern Baltica
The Neoproterozoic Timanide Orogen of eastern Baltiea extends from the high Arctic to the southern Ural Mountains and represents significant crustal growth of the northeastern European continental margin in the late Neoproterozoic. This volume, a co-operation between Western European and Russian scientists within the framework of the European Science Foundation’s EUROPROBE programme, provides a comprehensive overview of the orogen and represents a new synthesis of Timanian Orogeny. It includes: the pre-Timanian passive margin deposits of the northern and northeastern flank of the East European Craton; the magmatic, metamorphic and structural evolution of the orogen across the Timan Mountain and Pechora Basin regions to the Ural Mountains; the post-Timanian platform successions, important for interpreting the timing of orogeny and the return to an early Palaeozoic passive margin setting; and the extension of the orogen northwards to Novaya Zemlya. Relationships westwards to the Caledonides of Greenland and Scandinavia and eastwards to the Baikalides of Siberia are also treated.
This volume will be of interest to geoseientists, students and researchers concerned with orogenic processes and regional tectonics.