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UDC 551.243.8 (51)

https://doi.org/10.26516/2541-9641.2026.1.91

EDN: GVERGH

Changes in Late Cenozoic Volcanic Activities and Rock Composition Variations across the Central Tunka Valley of the Baikal Rift System

S.V. Rasskazov^1,2, I.S. Chuvashova^1,2, T.A. Yasnygina¹, K.A. Vinitsina², B.B. Budaev^2,3, O.Sh. Tsyrenov², A.P. Zambalov², V.Yu. Kononov², R.V. Antipin²

¹Institute of the Earth's Crust SB RAS, Irkutsk, Russia

²Irkutsk State University, Irkutsk, Russia

³V.B. Sochava Institute of Geography, SB RAS, Irkutsk, Russia

Abstract. Volcanism in the central Tunka Valley (in the Tunka Basin and Elovka interbasin uplift) occurred in the Middle Miocene (16–13 Myr ago), Late Miocene (11–8 Myr ago), and Pliocene–Pleistocene (4.0–0.8 Myr ago). In the southern core of the Tunka Valley (Irkut-Akhalik area), the composition of magmatic melts erupted during the Middle Miocene and Pliocene-Pleistocene volcanic intervals changed over time from basalts to trachybasalts, with a hiatus in volcanism from 13 to 4 Myr ago. In its northern core (Khobok area), basalts were followed with trachybasalts in the Middle Miocene (16–13 Myr ago), while in the Late Miocene (9–8 Myr ago) and the Pliocene–Pleistocene, only trachybasalts erupted. In the immediate southern mountainous framing (the Khamar-Daban Range) and northern mountainous framing (the Tunka Range), only Middle-Late Miocene volcanism occurred. Lava eruptions in the Tunka Valley 16–15 Myr ago, characterized by a homogeneous basaltic composition, mark the initial magmatism, coinciding in time with the triggering impulse of deep mantle magmatism at the axis of the Japan-Baikal geodynamic corridor that corresponded to the back-arc opening of the Sea of Japan Basin. Those of predominantly trachybasaltic composition 13, 11–8, and 4–0.8 Myr ago reflect the subsequent development of the Central Tunka zone of hot transtension under the fading activities in the Kamar-Stanovoy zone at the eastern end of the Tunka Valley.

Keywords: Baikal, Cenozoic, volcanism, basalt, trachybasalt, continental rifting

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Rasskazov Sergei Vasilevich,

doctor of geological and mineralogical sciences, professor,

664033, Irkutsk, st. Lermontova, 128,

Institute of the Earth's Crust SB RAS,

Head of the Laboratory for Isotopic and Geochronological Studies,

664025, Irkutsk, Lenin st., 3,

Irkutsk State University, Faculty of Geology,

Head of Dynamic Geology Char,

tel.: (3952) 51–16–59,

еmail: rassk@crust.irk.ru

 

Chuvashova Irina Sergeevna,

candidate of geological and mineralogical sciences,

664033, Irkutsk, st. Lermontova, 128,

Institute of the Earth's Crust SB RAS,

Senior Researcher,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

Associate Professor of Dynamic Geology Char,

еmail: chuvashova@crust.irk.ru

 

Yasnygina Tatyana Alexandrovna,

candidate of geological and mineralogical sciences,

664033, Irkutsk, st. Lermontova, 128,

Institute of the Earth's Crust SB RAS,

Senior Researcher,

еmail: ty@crust.irk.ru

 

Vinitsina Kristina Alexandrovna,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

еmail: kristya2651@yandex.ru

 

Budaev Bayar Buyantaevich,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

664033, Irkutsk, st. Ulaanbaatar 1,

V.B. Sochava Institute of Geography SB RAS,

graduate student,

еmail: bevabear7@gmail.com

 

Tsyrenov Oleg Zhargalovich,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

еmail: olegcyrenov@gmail.com

 

Zambalov Alexander Petrovich,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

еmail: zambalov1997@gmail.com

 

Kononov Vladislav Yurievich,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

еmail: ddoskononov@yandex.ru

 

Antipin Roman Vyacheslavovich,

664025, Irkutsk, st. Lenina, 3,

Irkutsk State University, Faculty of Geology,

second year student of master's degree program, correspondence department,

еmail: Antipin_roman@mail.ru