Геодинамика и тектонофизика (Jun 2021)

P–T CONDITIONS, U/Pb AND 40Ar/39Ar ISOTOPIC AGES OF UHT GRANULITES FROM CAPE KALTYGEI, WESTERN BAIKAL REGION

  • N. I. Volkova,
  • E. I. Mikheev,
  • A. V. Travin,
  • A. G. Vladimirov,
  • A. S. Mekhonoshin,
  • V. V. Khlestov

DOI
https://doi.org/10.5800/GT-2021-12-2-0526
Journal volume & issue
Vol. 12, no. 2
pp. 310 – 331

Abstract

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The study is focused on metapelitic granulites of Cape Kaltygei (Western Baikal region) that contain a diagnostic mineral assemblage of ultrahigh temperature (UHT) metamorphic rocks (orthopyroxene+sillimanite+quartz). The pseudosection-based thermobarometry yields peak metamorphic temperature and pressure values (T=950 °C, P=~9 kbar) and suggests near-isobaric cooling (IBC) conditions during the retrograde evolution of the granulites. The U/Pb zircon age estimates for metamorphism (~1.87 Ga) support the data published by other researchers. The SHRIMP-II U-Pb dating of zircon cores yields a minimum protolith age of 1.94–1.91 Ga. Biotites and amphiboles from granulites of Cape Kaltygei show the 40Ar/39Ar isotopic ages that are close to the Early Paleozoic accretion-collision system of the Western Baikal region.

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