Timanian blueschist-facies metamorphism in the Kvarkush metamorphic basement, Northern Urals, Russia
Monica Beckholmen, Johannes Glodny, 2004. "Timanian blueschist-facies metamorphism in the Kvarkush metamorphic basement, Northern Urals, Russia", The Neoproterozoic Timanide Orogen of Eastern Baltica, David G. Gee, Victoria Pease
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The core of the Kvarkush Anticline, on the western side of the Northern Urals, contains pre-Ordovician metasediments and minor metabasites that have undergone multistage deformation and transitional greenschist- to blueschist-facies metamorphism. Metamorphic conditions for the blueschist-facies assemblages are estimated at 350–400 °C and 7–8 kbar. The metamorphic rocks are cut by mafic dykes, one of which yields a Sm-Nd mineral age of 398 ± 37 Ma (2σ). The age of the high-pressure/low-temperature (HP/LT) metamorphism has been controversial. New Rb-Sr mineral data yield ages for the waning of blueschist-facies metamorphism at c. 536 Ma (535 ± 6 Ma, 535.8 ± 6.5 Ma, 536 ± 19 Ma, all 2σ), demonstrating that the specific conditions required for blueschist-facies metamorphism were attained in latest Neoproterozoic to earliest Cambrian times. The new data are the first well-constrained documentation of HP/LT metamorphism within the Timanian Orogen. We suggest that easterly-directed subduction of the East European continental margin (present-day coordinates) during the Timanian Orogeny, involving compressional thickening of the margin sediments, is the most likely scenario for the formation of the Kvarkush blueschists. The Kvarkush HP/LT metasediments, together with lower greenschist-facies and subgreenschist-facies metasediments further west, form parts of a Timanian orogenic wedge on an east-dipping thrust ramp. Reworking during the Uralian orogenesis was of minor importance.
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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.