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The Dzela complex, Polar Urals, Russia: a Neoproterozoic island arc

By
D. Remizov
D. Remizov
1
Institute of Geology, Komi Science Centre, Russian Academy of Sciences
54 Pervomayskaya Street, 167610 Syktyvkar, Russia
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V. Pease
V. Pease
2
Department of Geology and Geochemistry, Stockholm University, SE-106 91 Stockholm, and Laboratory for Isotope Geology, Swedish Natural History Museum
Stockholm, Sweden
vicky.pease@geo.su.se
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Published:
January 01, 2004

Abstract

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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Contents

Geological Society, London, Memoirs

The Neoproterozoic Timanide Orogen of Eastern Baltica

David G. Gee
David G. Gee
Uppsala University, Sweden
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Victoria Pease
Victoria Pease
Stockholm University, Sweden
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Geological Society of London
Volume
30
ISBN electronic:
9781862394056
Publication date:
January 01, 2004

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