Metamorphic evolution of ultrahigh-temperature Fe- and Al-rich granulites in the south Yenisei Ridge and tectonic implications


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Abstract

This study provides the first evidence for the occurrence of ultrahigh-temperature (UHT) granulite-facies metamorphism in the Yenisei Ridge (Angara–Kan block). UHT metamorphism is documented in Fe-Al-rich metapelites on the basis of the garnet–hypersthene–sillimanite–cordierite–plagioclase–biotite–spinel–quartz–K-feldspar assemblage. Microtextural relationships and compositional data for paragneisses of the Kan complex attest to three distinct metamorphic episodes: (M1) pre-peak prograde (820⎯900°C/5.5–7 kbar), (M2) peak UHT (920–1000°C/7–9 kbar), and (M3) post-peak retrograde (770⎯900°C/5.5–7.5 kbar). The observed counterclockwise P–T evolution at a high geothermal gradient (dT/dP = 100–200°C/kbar) suggests that UHT metamorphic assemblages were formed in an overall extensional tectonic setting accompanied by underplating of mantle-derived mafic magmas, which may be sourced from ~1750 Ma giant radiating dike swarms linked to the Vilyuy mantle plume as part of the Trans-Siberian LIP. The broad synchroneity of UHT metamorphism (1744 ± 26 Ma; monazite–zircon isochron age) and rift-related endogenic activity in the region can provide an additional line of evidence for the two-stage evolution of granulite-facies metamorphism in the Angara–Kan block. The Aldan–Stanovoy, Anabar, and Baikal basement inliers of high-grade metamorphic rocks within the Siberian craton record two Paleoproterozoic peaks (1.9 and 1.75 Ga) of granulite-facies metamorphism. The synchronous sequence of tectonothermal events at the periphery of the large Precambrian Laurentian, Baltica, and Siberian cratons provide convincing evidence for their spatial proximity over a wide time interval, which is consistent with the most recent paleomagnetic reconstructions of the Proterozoic supercontinent Nuna.

About the authors

I. I. Likhanov

Sobolev Institute of Geology and Mineralogy, Siberian Branch

Author for correspondence.
Email: likh@igm.nsc.ru
Russian Federation, pr. akademika Koptyuga 3, Novosibirsk, 630090

A. D. Nozhkin

Sobolev Institute of Geology and Mineralogy, Siberian Branch

Email: likh@igm.nsc.ru
Russian Federation, pr. akademika Koptyuga 3, Novosibirsk, 630090

V. V. Reverdatto

Sobolev Institute of Geology and Mineralogy, Siberian Branch

Email: likh@igm.nsc.ru
Russian Federation, pr. akademika Koptyuga 3, Novosibirsk, 630090

A. A. Krylov

Sobolev Institute of Geology and Mineralogy, Siberian Branch

Email: likh@igm.nsc.ru
Russian Federation, pr. akademika Koptyuga 3, Novosibirsk, 630090

P. S. Kozlov

Zavaritskii Institute of Geology and Geochemistry, Ural Branch

Email: likh@igm.nsc.ru
Russian Federation, Pochtovyi per. 7, Yekaterinburg, 620075

V. V. Khiller

Zavaritskii Institute of Geology and Geochemistry, Ural Branch

Email: likh@igm.nsc.ru
Russian Federation, Pochtovyi per. 7, Yekaterinburg, 620075

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