TY - JOUR

T1 - Metamorphic and chronological constraints on the early Paleozoic tectono-thermal evolution of the Olkhon Terrane, southern Siberia

AU - Li, Zhiyong

AU - Jiang, Yingde

AU - Collett, Stephen

AU - Štípská, Pavla

AU - Schulmann, Karel

AU - Wang, Sheng

AU - Sukhorukov, Vasiliy

N1 - ACKNOWLEDGEMENTS: This study was supported by the National Natural Science Foundation of China (42022017, 42021002), the International Partnership Program of CAS (132744KYSB20190039), and the Czech Science Foundation (grant number 19-27682X). The fieldwork was doneon the state assignment of IGM SB RAS with the finan-cial support of the Ministry of Science and Higher Educa-tion of the Russian Federation.

PY - 2023

Y1 - 2023

N2 - Terranes accreted to the southeastern margin of the Siberian Craton record an important early Paleozoic tectono-thermal event (known as the Baikal orogenic cycle) in the evolution of the Central Asian Orogenic Belt (CAOB). However, the precise metamorphic conditions and relative timing of this event and its linkage to the wider CAOB remain far poorly constrained. The best exposed of these terranes is the Olkhon Terrane on the western bank of Lake Baikal. Here, late Neoproterozoic through early Paleozoic island arc and back-arc assemblages were metamorphosed to form a thin granulite facies belt cropping out adjacent to the Siberian Craton and lower temperature/pressure paragneiss and migmatite towards the southeast. Phase equilibria modelling suggests that the granulite facies belt preserved moderate pressure (c. 0.80 GPa) and high temperature (up to 900°C) conditions while the paragneiss and migmatites in the southeast have peak metamorphic conditions around 700–770°C at 0.60–0.80 GPa. New geochronological data (zircon U–Pb in granulite and monazite U–Pb in paragneiss/migmatite) in combination with phase equilibria modelling and petro-structural analysis suggest that the tectono-metamorphic evolution of the Olkhon Terrane was controlled by a long-lasting (535–450 Ma) and pervasive thermal anomaly. Discrete maxima in the zircon and monazite U–Pb ages at c. 535, 500, and 450 Ma are linked to different stages of a semi-continuous high-temperature metamorphic evolution. Based on existing geological data of the region, a generalized geodynamic model for the Baikal orogenic cycle involving switching between compressional and extensional regimes during the early Paleozoic accretion of ‘exotic’ CAOB-derived material to the southern margin of Siberia is proposed. The tectono-metamorphic evolution of the Olkhon Terrane may represent a world-class example of polyphase shortening of a long-lived hot intra-continental arc–back-arc system during its collision with cratonic blocks.

AB - Terranes accreted to the southeastern margin of the Siberian Craton record an important early Paleozoic tectono-thermal event (known as the Baikal orogenic cycle) in the evolution of the Central Asian Orogenic Belt (CAOB). However, the precise metamorphic conditions and relative timing of this event and its linkage to the wider CAOB remain far poorly constrained. The best exposed of these terranes is the Olkhon Terrane on the western bank of Lake Baikal. Here, late Neoproterozoic through early Paleozoic island arc and back-arc assemblages were metamorphosed to form a thin granulite facies belt cropping out adjacent to the Siberian Craton and lower temperature/pressure paragneiss and migmatite towards the southeast. Phase equilibria modelling suggests that the granulite facies belt preserved moderate pressure (c. 0.80 GPa) and high temperature (up to 900°C) conditions while the paragneiss and migmatites in the southeast have peak metamorphic conditions around 700–770°C at 0.60–0.80 GPa. New geochronological data (zircon U–Pb in granulite and monazite U–Pb in paragneiss/migmatite) in combination with phase equilibria modelling and petro-structural analysis suggest that the tectono-metamorphic evolution of the Olkhon Terrane was controlled by a long-lasting (535–450 Ma) and pervasive thermal anomaly. Discrete maxima in the zircon and monazite U–Pb ages at c. 535, 500, and 450 Ma are linked to different stages of a semi-continuous high-temperature metamorphic evolution. Based on existing geological data of the region, a generalized geodynamic model for the Baikal orogenic cycle involving switching between compressional and extensional regimes during the early Paleozoic accretion of ‘exotic’ CAOB-derived material to the southern margin of Siberia is proposed. The tectono-metamorphic evolution of the Olkhon Terrane may represent a world-class example of polyphase shortening of a long-lived hot intra-continental arc–back-arc system during its collision with cratonic blocks.

KW - CAOB

KW - Olkhon Terrane

KW - monazite geochronology

KW - phase equilibria modelling

KW - zircon geochronology

UR - https://www.scopus.com/inward/record.url?eid=2-s2.0-85146339463&partnerID=40&md5=2367ede1eda5eabdf537b384d4b579a7

UR - https://www.mendeley.com/catalogue/3cc5977b-0f52-3dc1-9453-ee3d6e771237/

U2 - 10.1111/jmg.12706

DO - 10.1111/jmg.12706

M3 - Article

VL - 41

SP - 525

EP - 556

JO - Journal of Metamorphic Geology

JF - Journal of Metamorphic Geology

SN - 0263-4929

IS - 4

ER -