TY - JOUR

T1 - Regional, Contact Metamorphism, and Autometamorphism of the Olkhon Terrane (West Baikal Area)

AU - Sklyarov, E. V.

AU - Lavrenchuk, A. V.

AU - Fedorovsky, V. S.

AU - Gladkochub, D. P.

AU - Donskaya, T. V.

AU - Kotov, A. B.

AU - Mazukabzov, A. M.

AU - Starikova, A. E.

PY - 2020/1

Y1 - 2020/1

N2 - 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.

AB - 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.

KW - beerbachite

KW - hornfels

KW - metamorphism

KW - Olkhon terrane

KW - West Baikal Area

KW - ORTHO-PYROXENE

KW - THERMOMETRY

KW - MARGIN

KW - MA

KW - ROCKS

KW - LAKE BAIKAL

KW - PARAMETERS

UR - http://www.scopus.com/inward/record.url?scp=85083247409&partnerID=8YFLogxK

U2 - 10.1134/S0869591120010051

DO - 10.1134/S0869591120010051

M3 - Article

AN - SCOPUS:85083247409

VL - 28

SP - 47

EP - 61

JO - Petrology

JF - Petrology

SN - 0869-5911

IS - 1

ER -