Regional, Contact Metamorphism, and Autometamorphism of the Olkhon Terrane (West Baikal Area)

E. V. Sklyarov, A. V. Lavrenchuk, V. S. Fedorovsky, D. P. Gladkochub, T. V. Donskaya, A. B. Kotov, A. M. Mazukabzov, A. E. Starikova

Research output: Contribution to journalArticle

Abstract

The rocks of the Olkhon terrane experienced high-grade regional metamorphism reaching granulite facies. In addition to regional metamorphism, they were subjected to contact metamorphism and autometamorphism (mafic dikes). Three types of regional metamorphism have been distinguished. A terrane collage north of the Orso Zone revealed two stages of regional metamorphism: early-stage granulite metamorphism (Т = 750–900°С, Р = 8–9 kbar, around 500 Ma) and late-stage amphibolite and low–amphibolite facies (Т = 550–710°С, Р = 4–6 kbar, 460–470 Ma). The Orso microterrane separating the Krestovsky island-arc subterrane from a collage of other microterranes contains high-pressure mineral assemblages (up to 10 kbar), which are characterized by the presence of high-calcium garnet in metapelites. The Orso microterrane and Krestovsky subterrane are characterized by relatively high-pressure path of metamorphism. An extended zone of contact high-temperature metamorphism related to the emplacement of gabbro of the second phase of the Ustkrestovsky Complex has been mapped in the Krestovsky subterrane. The temperature of formation of two-pyroxene hornfels after metaporphyrites of the Birkhin volcanoplutonic association is estimated at 750–850°С. Beerbachites were formed by autometamorphism of subvolcanic mafic bodies, which compose the northern part of the Tazheran composite massif (syenite, Ne-syenite, subalkaline gabbro), dikes in the Birkhin gabbro massif, as well as dikes and separate blocks in marble mélange. The temperature of autometamorphism during formation of beerbachites is estimated from two-pyroxene geothermometer as 700–1000°С.

Original languageEnglish
Pages (from-to)47-61
Number of pages15
JournalPetrology
Volume28
Issue number1
DOIs
Publication statusPublished - Jan 2020

Keywords

  • beerbachite
  • hornfels
  • metamorphism
  • Olkhon terrane
  • West Baikal Area
  • ORTHO-PYROXENE
  • THERMOMETRY
  • MARGIN
  • MA
  • ROCKS
  • LAKE BAIKAL
  • PARAMETERS

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  • Cite this

    Sklyarov, E. V., Lavrenchuk, A. V., Fedorovsky, V. S., Gladkochub, D. P., Donskaya, T. V., Kotov, A. B., Mazukabzov, A. M., & Starikova, A. E. (2020). Regional, Contact Metamorphism, and Autometamorphism of the Olkhon Terrane (West Baikal Area). Petrology, 28(1), 47-61. https://doi.org/10.1134/S0869591120010051